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Approximately 15% of locally advanced colorectal cancers (CRC) have DNA mismatch repair deficiency (dMMR), resulting in high microsatellite instability and a high tumour mutational burden. These cancers are frequently sensitive to therapy with immune-checkpoint inhibitors (ICIs) in the metastatic setting. This sensitivity seems to be even more pronounced in locally advanced disease, and organ preservation has become a realistic aim in ongoing clinical trials involving patients with dMMR rectal cancer. By contrast, metastatic CRCs with proficient DNA mismatch repair (pMMR) are generally resistant to ICIs, although a proportion of locally advanced pMMR tumours seem to have a high degree of sensitivity to ICIs. In this Review, we describe the current and emerging clinical evidence supporting the use of neoadjuvant ICIs in patients with dMMR and pMMR CRC, and the potential advantages (based on a biological rationale) of such an approach. We discuss how neoadjuvant 'window-of-opportunity' trials are being leveraged to progress biomarker discovery and we provide an overview of potential predictive biomarkers of response to ICIs, exploring the challenges faced when evaluating such biomarkers in biopsy-derived samples. Lastly, we describe how these discoveries might be used to drive a rational approach to trialling novel immunotherapeutic strategies in patients with pMMR CRC, with the ultimate aim of disease eradication and the generation of long-term immunosurveillance., Competing Interests: Competing interests C.J.M.W. has received institutional research funding from GSK, Merck Serono, and Roche Diagnostics and honoraria from Merck Serono, Roche Diagnostics, Servier and Tactics MD. A.M.P. has received institutional research funding from GSK. P.M.K. has received institutional research funding from Agenus. J.F.S. has received institutional research funding from Amgen, GSK, Merck Serono, and Pierre Fabre Medicament and honoraria from AstraZeneca, Biocartis, BMS, GSK, Jazz Pharmaceuticals, Merck Serono, Pierre Fabre Medicament, Roche Diagnostics, Sanofi, Seagen, Servier and Takeda. C.S.R. has received institutional research funding from GSK. G.W.M. has received institutional research funding from AstraZeneca. S.T. has received institutional research funding from GSK., (© 2024. Springer Nature Limited.)

Circulating tumor cells (CTCs) enumeration and molecular profiling hold promise in revolutionizing the management of solid tumors. Their understanding has evolved significantly over the past two decades, encompassing pivotal biological discoveries and clinical studies across various malignancies. While for some tumor types, such as breast, prostate, and colorectal cancer, CTCs are ready to enter clinical practice, for others, additional research is required. CTCs serve as versatile biomarkers, offering insights into tumor biology, metastatic progression, and treatment response. This review summarizes the latest advancements in CTC research and highlights future directions of investigation. Special attention is given to concurrent evaluations of CTCs and other circulating biomarkers, particularly circulating tumor DNA. Multi-analyte assessment holds the potential to unlock the full clinical capabilities of liquid biopsy. In conclusion, CTCs represent a transformative biomarker in precision oncology, offering extraordinary opportunities to translate scientific discoveries into tangible improvements in patient care., Competing Interests: Declaration of Competing Interest Singhal S. has received consulting fees from Oncohost. Fusco N. has received honoraria for consulting, advisory role, speaker bureau, travel, and/or research grants from Merck Sharp & Dohme (MSD), Merck, Novartis, AstraZeneca, Roche, Menarini, Daiichi Sankyo, GlaxoSmithKline (GSK), Gilead, Adicet Bio, Sysmex, Reply, Veracyte Inc., Sakura, Leica Biosystems, Lilly. Cristofanilli M reports personal fees from Lilly, Sermonix, Data Genomics, Foundation Medicine, Guardant Health, Celcuity, Iylon, and Ellipses and grants and personal fees from Pfizer, AZ and Menarini. The other authors have no conflicts of interest to declare. Rolfo C. is a speaker for Merck Sharp and Dohme, AstraZeneca, COR2ED, Daiichi Sankyo, Physicians Education Resource, and Roche (CH); has research collaborations (nonfinancial support) with Guardant Health; advisory board activity: Archer, Inivata, Bayer U.C. LLC, Boston pharmaceutical, CEA, MD Serono, General Dynamics, MedStar, Novartis, Sanofi Genzyme-Regeneron. Provides expert testimony to Intellisphere, scientific board for Imagene, and is a coordinating PI for MD Serono Global PI LUNG itrapid@024 trial. Research grant from LCRF-Pfizer unrelated to the current work. Gandara D.R. received honoraria from Merck, research funding from Merck, Amgen, Genentech, AstraZeneca, Astex Pharmaceuticals, and has consulting or advisory role for AstraZeneca, Guardant Health, OncoCyte, IO Biotech, Roche/Genentech, and Adagene. Kasi P.M. reports personal fees from Foundation Medicine, MSD Oncology/Merck, Tempus, Bayer, Lilly, Delcath Systems, QED Therapeutics, Servier, Taiho Oncology, Exact Sciences, Daiichi Sankyo/AstraZeneca, Eisai, Seattle Genetics, SAGA Diagnostics, Illumina, BostonGene, Guardant Health, and Taiho; personal fees and other support from Elicio Therapeutics; other support from Precision Biosensors Inc.; and grants from Merck, Novartis, and Agenus Bio. Malapelle U. received personal fees (consultant and/or speaker bureau) from Boehringer Ingelheim, Roche, MSD, Amgen, Thermo Fisher Scientifics, Eli Lilly, Diaceutics, GSK, AstraZeneca, Janssen, Diatech, Novartis, and Hedera. The other authors declare no competing interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Immune thrombocytopenia (ITP) secondary to durvalumab, a programmed cell death ligand 1 inhibitor, is a rare but clinically significant immune-related adverse event. Herein, we present 2 patients with cholangiocarcinoma who developed ITP immediately post-yttrium-90 radioembolization (Y90-RE) while on durvalumab-based systemic therapy. We hypothesize that given the timing, the immunotherapy and the radioembolization combination led to this event. It is not uncommon given the approval of immunotherapy and its role in locoregional therapies, that patients are treated with a combination of systemic immunotherapy and radioembolization or other forms of radiation, thus signifying the importance of potential complications., Case Presentation: Two patients, a 67-year-old female and a 60-year-old man, with biopsy-proven advanced unresectable cholangiocarcinoma, received a combination of systemic therapy with durvalumab, gemcitabine, and cisplatin and subsequently Y90-RE. Both patients developed ITP following in the immediate post-Y90-RE period. All other causes of ITP were comprehensively ruled out and treatment for ITP was initiated in the form of high-dose steroid and intravenous immunoglobulins. Durvalumab was discontinued, and only gemcitabine/cisplatin-based chemotherapy was continued thereafter. Due to recurrence, one of the patients required longer courses of steroids as well as thrombopoietin receptor agonists., Conclusion: Immunotherapy in the form of durvalumab and now pembrolizumab alongside chemotherapy is an approved first-line standard of care. Furthermore, it is not uncommon for patients to receive Y90-RE to improve patient outcomes. This report highlights the development of ITP in 2 patients who received durvalumab alongside Y90-RE. Awareness of this as a potential immune-mediated event is important to allow for close monitoring of platelet counts and for early intervention/management when this occurs., Competing Interests: P.M.K. reports grants paid to the institution by Merck, Agenus Bio, Novartis, Advanced Accelerator Applications, TerSera, and Boston Scientific; a consultancy and advisory board relationship with Elicio (scientific advisory board member/shares/stock ownership); cofounder of Precision BioSensors Inc.; consultancy/advisory board fees from Guardant Health, Natera, Foundation Medicine, Illumina, BostonGene, Merck/MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, IPBA, QED Therapeutics, Boston Healthcare Associates, Servier, Taiho Oncology, Exact Sciences, Daiichi Sankyo/AstraZeneca, Eisai, Saga Diagnostics, NeoGenomics, DoMore Diagnostics AS, and Seattle Genetics; consulting fees paid to the institution by Taiho Pharmaceutical and Ipsen; receiving travel support from AstraZeneca for presentation of an investigator-initiated trial. All other authors have no conflicts of interest to report., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

Introduction: Personalized and tumor-informed circulating tumor DNA (ctDNA) testing is feasible and allows for molecular residual disease (MRD) identification in patients with pancreatic ductal adenocarcinoma (PDAC)., Methods: In this retrospective analysis of commercial cases from multiple US institutions, personalized, tumor-informed, whole-exome sequenced, and germline-controlled ctDNA levels were quantified and analyzed in patients with PDAC. Plasma samples (n = 1329) from 298 clinically validated patients were collected at diagnosis, perioperatively (MRD-window; within 2-12 weeks after surgery, before therapy), and during surveillance (>12 weeks post-surgery if no ACT or starting 4 weeks post-ACT) from November 2019 to March 2023., Results: Of the initially diagnosed patients with stages I-III PDAC who went for resection, the median follow-up time from surgery was 13 months (range 0.1-214). Positive ctDNA detection rates were 29% (29/100) and 29.6% (45/152) during the MRD and surveillance windows, respectively. Positive ctDNA detection was significantly associated with shorter DFS within the MRD window (median DFS of 6.37 months for ctDNA-positive vs 33.31 months for ctDNA-negative patients; HR: 5.45, P < .0001) as well as during the surveillance period (median DFS: 11.40 months for ctDNA-positive vs NR for ctDNA-negative; HR: 12.38, P < .0001). Additionally, DFS was significantly better with KRAS wildtype status followed by KRASG12R (HR: 0.99, P = .97), KRASG12D (HR: 1.42, P = .194), and worse with KRASG12V (HR: 2.19, P = .002) status. In multivariate analysis, ctDNA detection at surveillance was found to be the most significant prognostic factor for recurrence (HR: 24.28, P < .001)., Conclusions: Perioperative tumor-informed ctDNA detection in PDAC is feasible across all stages and is associated with patient survival outcomes., (© The Author(s) 2024. Published by Oxford University Press.)

Purpose: The new CAP guideline published in August 2022 recommends using immunohistochemistry (IHC) to test for mismatch repair defects in gastroesophageal (GE), small bowel (SB), or endometrial carcinoma (EC) cancers over next-generation sequencing assessment of microsatellite instability (NGS-MSI) for immune checkpoint inhibitor (ICI) therapy eligibility and states there is a preference to use IHC over NGS-MSI in colorectal carcinoma (CRC)., Methods: We assessed the concordance of NGS-MSI and IHC-MMR from a very large cohort across the spectrum of solid tumors., Results: Of the over 190,000 samples with both NGS-MSI and IHC-MMR about 1,160 were initially flagged as discordant. Of those samples initially flagged as discordant, 50.9% remained discordant after being reviewed by an additional pathologist. This resulted in a final discordance rate of 0.31% (590/191,767). Among CRC, GE, SB and EC, 55.4% of mismatch repair proficient/MSI high (MMRp/MSI-H) tumors had at least one somatic pathogenic mutation in an MMR gene or POLE . Mismatch repair deficient/microsatellite stable (MMRd/MSS) tumors had a significantly lower rate of high tumor mutational burden than MMRp/MSI-H tumors. Across all solid tumors, MMRd/MSI-H tumors had significantly longer overall survival (OS; hazard ratio [HR], 1.47, P < .001) and post-ICI survival (HR, 1.82, P < .001) as compared with MMRp/MSS tumors. The OS for the MMRd/MSS group was slightly worse compared to the MMRp/MSI-H tumors, but this difference was not statistically significant (HR, 0.73, P = .058), with a similar pattern when looking at post-ICI survival (HR, 0.43, P = .155)., Conclusion: This study demonstrates that NGS-MSI is noninferior to IHC-MMR and can identify MSI-H tumors that IHC-MMR is unable to detect and conversely IHC-MMR can identify MMRd tumors that NGS-MSI misses.

Background: Cholangiocarcinoma-with a growing incidence rate and poor prognosis-is not an uncommon cancer. Molecular profiling can reveal actionable aberrations in at least a third of the tumors. This is especially so in the case of intrahepatic cholangiocarcinoma (ICC), where mutations in the isocitrate dehydrogenase 1 and 2 genes ( IDH1/2 ) make up 15%-20% of these tumors. IDH1/2 mutant ICC is a rare disease that has not been adequately reported. To expand the spectrum of findings seen in these patients, we present a single institution case series., Methods and Results: We descriptively characterize the clinical, radiological, and histopathological findings of 12 such patients. IDH1/2 mutant ICC was found in elderly women, with two-thirds of patients having additional co-mutations. Anecdotally, patients who did receive systemic and/or locoregional therapies had long-term durable outcomes., Conclusion: Our findings indicate an increasing need to personalize an approach for these patients with specific molecular alterations. With the advent of the IDH1 inhibitor ivosidenib and other inhibitors in this space, IDH1/2 mutation have both prognostic and predictive value. Our series builds upon the patterns and findings seen in these patients., Competing Interests: Declaration of Conflicts of InterestThe authors declare the following financial interests/personal relationships which may be considered as potential competing interests: PMK reports grants paid to the institution by Merck, Agenus Bio, Novartis, Advanced Accelerator Applications, Tersera, and Boston Scientific; a consultancy and advisory board relationship with Elicio (scientific advisory board member/shares/stock ownership); cofounder of Precision BioSensors Inc.; consultancy/advisory board fees from Guardant Health, Natera, Foundation Medicine, Illumina, BostonGene, Merck/MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, IPBA, QED Therapeutics, Boston Healthcare Associates, Servier, Taiho Oncology, Exact Sciences, Daiichi Sankyo/AstraZeneca, Eisai, Saga Diagnostics, Neogenomics, Do More Diagnostics AS, and Seattle Genetics; consulting fees paid to the institution by Taiho Pharmaceutical and Ipsen; receiving travel support from AstraZeneca for presentation of an investigator-initiated trial. All other authors have no conflicts of interest to report.

Background: Doublet platinum or taxane-based therapies are the current standard backbone of treatment for advanced gastric/gastroesophageal junction (GEJ) adenocarcinoma. Previously used anthracycline-based triplet regimens are no longer used routinely due to toxicity and lack of superior efficacy. We hypothesized that the addition of nab-paclitaxel to FOLFOX (FOLFOX-A) would induce higher efficacy and better tolerability., Patients and Methods: Eligible patients with chemotherapy-naïve advanced unresectable HER2-negative gastric or GEJ adenocarcinoma were enrolled in this phase II single-arm trial of FOLFOX (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, 5-FU 2400 mg/m2 over 46-48 hours) + nab-paclitaxel (150 mg/m2) every 14 days of a 28-day cycle. Evaluable disease according to RECIST v1.1 for solid tumors was required. The primary endpoint was the objective response rate. Simon's optimal 2-stage design was used to test 5% versus 20% response rate with 90% power and 10% one-sided type I error rate., Results: The study enrolled 39 patients. Median age was 63 (range 20-80) years, 30 (77%) were male, 34 (94%) were White, and 21 (57%) had gastric tumors. The median number of cycles completed was 4.5 (range: 0-36), and 25 patients required dose reductions or discontinuation of at least one component due to toxicity. Of the 38 patients evaluable for response, 15 (42.9%) had complete/partial response (CR/PR) as the best response, and 13 (37.1%) had stable disease. progression-free survival (PFS) and OS data were available for 38 patients, with a median follow-up duration of 27 months (range: 18.2-51.9 months for censored patients). Median PFS was 6.6 months (95% CI: 5.6-12.9), with 31.0% (95% CI: 18.4%-52.4%) 12-month PFS rate. The median OS was 10.5 months (95% CI: 8.8-20.7), 12-month OS rate was 44.7% (95% CI: 31.4%-63.7%). Treatment-related grade 3-4 toxicities included peripheral sensory neuropathy and anemia (18.4% each), neutropenia (15.8%), and diarrhea and lymphopenia (7.9% each)., Conclusions: FOLFOX-A has a significant response rate, expected toxicities, and should be considered for future investigation in combination with immunotherapy given the recent approvals., (© The Author(s) 2024. Published by Oxford University Press.)

Purpose: Cancer of unknown primary (CUP) is a syndrome comprising metastatic cancers without a clinically identified primary site. Although patients with CUP have an unfavorable prognosis, treatment with site-specific therapies guided by clinical features, standard pathology, and molecular assays can improve overall survival. The 92-gene assay (CancerTYPE ID) is a gene expression-based classifier that helps identify the tissue of origin for metastatic cancers with unknown or uncertain diagnoses. This study reports the frequency of selected molecular aberrations of oncogenes, including KRAS , IDH1/2 , BRCA1/2 , and BRAF , in patients with CUP in the MOSAIC database to highlight potential treatment options., Methods: MOSAIC is a database of patients with CUP submitted for CancerTYPE ID testing and NeoTYPE biomarker testing. Tumor biopsy samples were analyzed by CancerTYPE ID for tumor type identification and further tested for molecular aberrations of oncogenes, including KRAS , IDH1/2 , BRCA1/2 , and BRAF ., Results: CancerTYPE ID identified a specific tumor type in 92.5% (2,929 of 3,168) of CUP cases in the MOSAIC database. The most commonly identified histological type was adenocarcinoma (75.4%), with pancreaticobiliary being the most common molecularly diagnosed cancer (24.9%). Aberrations in KRAS , IDH1/2 , BRCA , and BRAF genes were identified in 18.8% (n = 597) of biopsies. A cancer-specific US Food and Drug Administration (FDA)-approved or investigational targeted therapy was potentially available for 24.6% (n = 147) of these patients., Conclusion: This retrospective analysis supports incorporating CancerTYPE ID into the evaluation for patients with CUP to help determine the tissue of origin and identify actionable genetic alterations. This approach may allow more patients with CUP to benefit from site-specific FDA-approved targeted therapies or enrollment into clinical trials.

Purpose: Genomic rearrangements can generate potent oncogenic drivers or disrupt tumor suppressor genes. This study examines the landscape of fusions and rearrangements detected by liquid biopsy (LBx) of circulating tumor DNA (ctDNA) across different cancer types., Experimental Design: LBx from 53,842 patients with 66 solid tumor types were profiled using FoundationOneLiquid CDx, a hybrid-capture sequencing platform that queries 324 cancer-related genes. Tissue biopsies (TBx) profiled using FoundationOneCDx were used as a comparator., Results: Among all LBx, 7,377 (14%) had ≥1 pathogenic rearrangement detected. A total of 3,648 (6.8%) LBx had ≥1 gain-of-function (GOF) oncogene rearrangement, and 4,428 (8.2%) LBx had ≥1 loss-of-function rearrangement detected. Cancer types with higher prevalence of GOF rearrangements included those with canonical fusion drivers: prostate cancer (19%), cholangiocarcinoma (6.4%), bladder (5.5%), and non-small cell lung cancer (4.4%). Although the prevalence of driver rearrangements was lower in LBx than TBx overall, the frequency of detection was comparable in LBx with a tumor fraction (TF) ≥1%. Rearrangements in FGFR2, BRAF, RET, and ALK, were detected across cancer types, but tended to be clonal variants in some cancer types and potential acquired resistance variants in others., Conclusions: In contrast to some prior literature, this study reports detection of a wide variety of rearrangements in ctDNA. The prevalence of driver rearrangements in tissue and LBx was comparable when TF ≥1%. LBx presents a viable alternative when TBx is not available, and there may be less value in confirmatory testing when TF is sufficient., (©2023 The Authors; Published by the American Association for Cancer Research.)

Pancreatic and colorectal cancers are often KRAS mutated and are incurable when tumor DNA or protein persists or recurs after curative intent therapy. Cancer vaccine ELI-002 2P enhances lymph node delivery and immune response using amphiphile (Amph) modification of G12D and G12R mutant KRAS (mKRAS) peptides (Amph-Peptides-2P) together with CpG oligonucleotide adjuvant (Amph-CpG-7909). We treated 25 patients (20 pancreatic and five colorectal) who were positive for minimal residual mKRAS disease (ctDNA and/or serum tumor antigen) after locoregional treatment in a phase 1 study of fixed-dose Amph-Peptides-2P and ascending-dose Amph-CpG-7909; study enrollment is complete with patient follow-up ongoing. Primary endpoints included safety and recommended phase 2 dose (RP2D). The secondary endpoint was tumor biomarker response (longitudinal ctDNA or tumor antigen), with exploratory endpoints including immunogenicity and relapse-free survival (RFS). No dose-limiting toxicities were observed, and the RP2D was 10.0 mg of Amph-CpG-7909. Direct ex vivo mKRAS-specific T cell responses were observed in 21 of 25 patients (84%; 59% both CD4 + and CD8 + ); tumor biomarker responses were observed in 21 of 25 patients (84%); biomarker clearance was observed in six of 25 patients (24%; three pancreatic and three colorectal); and the median RFS was 16.33 months. Efficacy correlated with T cell responses above or below the median fold increase over baseline (12.75-fold): median tumor biomarker reduction was -76.0% versus -10.2% (P < 0.0014), and the median RFS was not reached versus 4.01 months (hazard ratio = 0.14; P = 0.0167). ELI-002 2P was safe and induced considerable T cell responses in patients with immunotherapy-recalcitrant KRAS-mutated tumors. ClinicalTrials.gov identifier: NCT04853017 ., (© 2024. The Author(s).)

Colorectal cancer is the third most common cancer worldwide, and incidence is rising in younger individuals. Anti-EGFR antibodies, including cetuximab and panitumumab, have been incorporated into standard-of-care practice for patients with advanced disease. Herein, we review the molecular characteristics of these agents and the trials that lead to their approvals. Further, we discuss clinical implications of data regarding biomarkers that dictate treatment selection, different dosing strategies, and side effect management. Finally, we look towards the future and describe contexts in which these agents are currently being investigated clinically with a focus on combinations with MAPK-targeted therapies and immunotherapy. Overall, this review provides historical context, current clinical usage, and future directions for anti-EGFR antibodies in advanced colorectal cancer., (© The Author(s) 2023. Published by Oxford University Press.)

Objective: Most of the work in terms of liquid biopsies in patients with solid tumors is focused on circulating tumor DNA (ctDNA). Our aim was to evaluate the feasibility of using circulating tumor cells (CTCs) in peripheral blood samples from patients with advanced or metastatic gastrointestinal (GI) cancers., Methods: In this prospective study, blood samples were collected from each patient in 2 AccuCyte ® blood collection tubes and each tube underwent CTC analysis performed utilizing the RareCyte ® platform. The results from both tubes were averaged and a total of 150 draws were done, with 281 unique reported results. The cadence of sampling was based on convenience sampling and piggybacked onto days of actual clinical follow-ups and treatment visits. The CTC results were correlated with patient- and tumor-related variables., Results: Data from a total of 59 unique patients were included in this study. Patients had a median age of 58 years, with males representing 69% of the study population. More than 57% had received treatment prior to taking blood samples. The type of GI malignancy varied, with more than half the patients having colorectal cancer (CRC, 54%) followed by esophageal/gastric cancer (17%). The least common cancer was cholangiocarcinoma (9%). The greatest number of CTCs were found in patients with colorectal cancer (Mean: 15.8 per 7.5 ml; Median: 7.5 per 7.5 ml). In comparison, patients with pancreatic cancer (PC) had considerably fewer CTCs (Mean: 4.2 per 7.5 ml; Median: 3 per 7.5 ml). Additionally, we found that patients receiving treatment had significantly fewer CTCs than patients who were not receiving treatment (Median 2.7 versus 0.7). CTC numbers showed noteworthy disparities between patients with responding/stable disease in comparison to those with untreated/progressive disease (Median of 2.7 versus 0). When CTCs were present, biomarker analyses of the four markers human epidermal growth factor receptor 2 (HER2)/programmed death-ligand 1 (PD-L1)/Kiel 67 (Ki-67)/epidermal growth factor receptor (EGFR) was feasible. Single cell sequencing confirmed the tumor of origin., Conclusion: Our study is one of the first prospective real-time studies evaluating CTCs in patients with GI malignancies. While ctDNA-based analyses are more common in clinical trials and practice, CTC analysis provides complementary information from a liquid biopsy perspective that is of value and worthy of continued research., Competing Interests: Author PK reports grants paid to the institution by Merck, Agenus Bio, Novartis, Advanced Accelerator Applications, Tersera, and Boston Scientific; a consultancy and advisory board relationship with Elicio scientific advisory board member/shares/stock ownership; consultancy/advisory board fees from Guardant Health, Natera, Foundation Medicine, Illumina, BostonGene, Merck/MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, IPBA, QED Therapeutics, Boston Healthcare Associates, Servier, Taiho Oncology, Exact Sciences, Daiichi Sankyo/AstraZeneca, Eisai, Saga Diagnostics, Neogenomics, Do More Diagnostics AS, and Seattle Genetics; consulting fees paid to the institution by Taiho Pharmaceutical and Ipsen; receiving travel support from AstraZeneca for presentation of an investigator-initiated trial. Authors LC, AR, and TG are employees of RareCyte. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Malkawi, Lutfi, Afghan, Shah, Costandy, Ramirez, George, Toor, Salem and Kasi.)

In patients with locally advanced cancer without distant metastases, the neoadjuvant setting presents a platform to evaluate new drugs. For mismatch repair proficient/microsatellite stable (pMMR/MSS) colon and rectal cancer, immunotherapy has shown limited efficacy. Herein, we report exceptional responses observed with neoadjuvant botensilimab (BOT), an Fc-enhanced next-generation anti-CTLA-4 antibody, alongside balstilimab (BAL; an anti-PD-1 antibody) in two patients with pMMR/MSS colon and rectal cancer. The histological pattern of rapid immune response observed ("inside-out" (serosa-to-mucosa) tumor regression) has not been described previously in this setting. Spatial biology analyses (RareCyte Inc.) reveal mechanisms of actions of BOT, a novel innate-adaptive immune activator. These observations have downstream implications for clinical trial designs using neoadjuvant immunotherapy and potentially sparing patients chemotherapy., (© 2023. The Author(s).)

Purpose: Immune checkpoint inhibitors are approved for advanced solid tumors with microsatellite instability-high (MSI-H). Although several technologies can assess MSI-H status, detection and outcomes with circulating tumor DNA (ctDNA)-detected MSI-H are lacking. As such, we examined pan-cancer MSI-H prevalence across 21 cancers and outcomes after ctDNA-detected MSI-H., Methods: Patients with advanced cancer who had ctDNA testing (Guardant360) from October 1, 2018, to June 30, 2022, were retrospectively assessed for prevalence. GuardantINFORM, which includes anonymized genomic and structured payer claims data, was queried to assess outcomes. Patients who initiated new treatment within 90 days of MSI-H detection were sorted into immunotherapy included in treatment (IO) or no immunotherapy included (non-IO) groups. Real-world time to treatment discontinuation (rwTTD) and real-world time to next treatment (rwTTNT) were assessed in months as proxies of progression-free survival (PFS); real-world overall survival (rwOS) was assessed in months. Cox regression tests analyzed differences. Colorectal cancer, non-small-cell lung cancer (NSCLC), prostate cancer, gastroesophageal cancer, and uterine cancer (UC) were assessed independently; all other cancers were grouped., Results: In total, 1.4% of 171,881 patients had MSI-H detected. Of 770 patients with outcomes available, rwTTD and rwTTNT were significantly longer for patients who received IO compared with non-IO for all cancers ( P ≤ .05; hazard ratio [HR] range, 0.31-0.52 and 0.25-0.54, respectively) except NSCLC. rwOS had limited follow-up for all cohorts except UC (IO 39 v non-IO 23 months; HR, 0.18; P = .004); however, there was a consistent trend toward prolonged OS in IO-treated patients., Conclusion: These data support use of a well-validated ctDNA assay to detect MSI-H across solid tumors and suggest prolonged PFS in patients treated with IO-containing regimens after detection. Tumor-agnostic, ctDNA-based MSI testing may be reliable for rapid decision making.

Metastatic colorectal cancer (mCRC) is a heterogeneous disease that can evoke discordant responses to therapy among different lesions in individual patients. The Response Evaluation Criteria in Solid Tumors (RECIST) criteria do not take into consideration response heterogeneity. We explored and developed lesion-based measurement response criteria to evaluate their prognostic effect on overall survival (OS)., Patients and Methods: Patients enrolled in 17 first-line clinical trials, who had mCRC with ≥ 2 lesions at baseline, and a restaging scan by 12 weeks were included. For each patient, lesions were categorized as a progressing lesion (PL: > 20% increase in the longest diameter (LD)), responding lesion (RL: > 30% decrease in LD), or stable lesion (SL: neither PL nor RL) based on the 12-week scan. Lesion-based response criteria were defined for each patient as follows: PL only, SL only, RL only, and varied responses (mixture of RL, SL, and PL). Lesion-based response criteria and OS were correlated using stratified multivariable Cox models. The concordance between OS and classifications was measured using the C statistic., Results: Among 10,551 patients with mCRC from 17 first-line studies, varied responses were noted in 51.6% of patients, among whom, 3.3% had RL/PL at 12 weeks. Among patients with RL/SL, 52% had stable disease (SD) by RECIST 1.1, and they had a longer OS (median OS (mOS) = 19.9 months) than those with SL only (mOS = 16.8 months, HR (95% CI) = 0.81 (0.76, 0.85), p < 0.001), although a shorter OS than those with RL only (mOS = 25.8 months, HR (95% CI) = 1.42 (1.32, 1.53), p < 0.001). Among patients with SL/PL, 74% had SD by RECIST 1.1, and they had a longer OS (mOS = 9.0 months) than those with PL only (mOS = 8.0 months, HR (95% CI) = 0.75 (0.57, 0.98), p = 0.040), yet a shorter OS than those with SL only (mOS = 16.8 months, HR (95% CI) = 1.98 (1.80, 2.18), p < 0.001). These associations were consistent across treatment regimen subgroups. The lesion-based response criteria showed slightly higher concordance than RECIST 1.1, although it was not statistically significant., Conclusion: Varied responses at first restaging are common among patients receiving first-line therapy for mCRC. Our lesion-based measurement criteria allowed for better mortality discrimination, which could potentially be informative for treatment decision-making and influence patient outcomes.

Background: HER2 is an actionable target in metastatic colorectal cancer. We assessed the activity of tucatinib plus trastuzumab in patients with chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer., Methods: MOUNTAINEER is a global, open-label, phase 2 study that enrolled patients aged 18 years and older with chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer at 34 sites (clinics and hospitals) in five countries (Belgium, France, Italy, Spain, and the USA). Initially, the study was designed as a single-cohort study, which was expanded following an interim analysis to include more patients. Initially, patients were given tucatinib (300 mg orally twice daily) plus intravenous trastuzumab (8 mg/kg as an initial loading dose, then 6 mg/kg every 21 days; cohort A) for the duration of treatment (until progression), and after expansion, patients were randomly assigned (4:3), using an interactive web response system and stratified by primary tumour location, to either tucatinib plus trastuzumab (cohort B) or tucatinib monotherapy (cohort C). The primary endpoint was confirmed objective response rate per blinded independent central review (BICR) for cohorts A and B combined and was assessed in patients in the full analysis set (ie, patients with HER2-positive disease who received at least one dose of study treatment). Safety was assessed in all patients who received at least one dose of study treatment. This trial is registered with ClinicalTrials.gov, NCT03043313, and is ongoing., Findings: Between Aug 8, 2017, and Sept 22, 2021, 117 patients were enrolled (45 in cohort A, 41 in cohort B, and 31 in cohort C), of whom 114 patients had locally assessed HER2-positive disease and received treatment (45 in cohort A, 39 in cohort B, and 30 in cohort C; full analysis set), and 116 patients received at least one dose of study treatment (45 in cohort A, 41 in cohort B, and 30 in cohort C; safety population). In the full analysis set, median age was 56·0 years (IQR 47-64), 66 (58%) were male, 48 (42%) were female, 88 (77%) were White, and six (5%) were Black or African American. As of data cutoff (March 28, 2022), in 84 patients from cohorts A and B in the full analysis set, the confirmed objective response rate per BICR was 38·1% (95% CI 27·7-49·3; three patients had a complete response and 29 had a partial response). In cohorts A and B, the most common adverse event was diarrhoea (55 [64%] of 86), the most common grade 3 or worse adverse event was hypertension (six [7%] of 86), and three (3%) patients had tucatinib-related serious adverse events (acute kidney injury, colitis, and fatigue). In cohort C, the most common adverse event was diarrhoea (ten [33%] of 30), the most common grade 3 or worse adverse events were increased alanine aminotransferase and aspartate aminotransferase (both two [7%]), and one (3%) patient had a tucatinib-related serious adverse event (overdose). No deaths were attributed to adverse events. All deaths in treated patients were due to disease progression., Interpretation: Tucatinib plus trastuzumab had clinically meaningful anti-tumour activity and favourable tolerability. This treatment is the first US Food and Drug Administration-approved anti-HER2 regimen for metastatic colorectal cancer and is an important new treatment option for chemotherapy-refractory HER2-positive metastatic colorectal cancer., Funding: Seagen and Merck & Co., Competing Interests: Declaration of interests JHS reports support from Seagen for the present manuscript; grants paid to the institution by Amgen, Bayer, Erasca, Seagen, Daiichi-Sankyo, Gossamer Bio, AStar D3, Sanofi, Roche/Genentech, Curegenix, Nektar, AbbVie, and Silverback Therapeutics; receiving consulting fees from AbbVie, Takeda, AstraZeneca, Bayer, GlaxoSmithKline, Inivata, Mereo Biopharma, Pfizer, Roche/Genentech, Seagen, Silverback Therapeutics, and Viatris; receiving honoraria from Bayer, Natera, and Pfizer; receiving travel support from Seagen and Guardant Health; receiving other services from Guardant Health; and is a member of advisory boards for AbbVie and Pionyr Immunotherapeutics. AC reports grants paid to their institution by Seagen, GlaxoSmithKline, and Inspira (previously RGenix) and receiving advisory or consultancy fees from Bayer, Merck, Seagen, GlaxoSmithKline, Janssen, and G1 Therapeutics. SS is a member of advisory boards for Agenus, AstraZeneca, Bayer, Bristol Myers Squibb, CheckmAb, Daiichi-Sankyo, Guardant Health, Menarini, Merck, Novartis, Pierre-Fabre, Roche-Genentech, and Seagen. TA reports attending advisory board meetings and receiving consulting fees from Astellas, Aptitude Health, Bristol Myers Squibb, Gritstone Oncology, GamaMabs Pharma Sa, GlaxoSmithKline, Gilead, Kaleido Oncology, Merck & Co, Pierre Fabre, Seagen, Servier Transgène, and Roche/Ventana; receiving support for attending meetings from Bristol Myers Squibb, Merck & Co, and Servier; and receiving honoraria for speaking, manuscript writing, or educational events from AstraZeneca, Bristol Myers Squibb, Gritstone Oncology, GlaxoSmithKline, Merck & Co, Pierre Fabre, Seagen, Roche/Ventana, Sanofi, and Servier; and receiving travel support from Bristol Myers Squibb and Merck & Co. KN reports grants from Pharmavite, Revolution Medicines, Evergrande Group, and Janssen and receiving consultancy fees from Bayer, Seagen, X-Biotix Therapeutics, Array Biopharma, BiomX, Bicara Therapeutics, GlaxoSmithKline, Pfizer, and Redesign Health. EVC reports grants paid to the institution by Amgen, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Ipsen, Lilly, Merck Sharp & Dohme, Merck KGaA, Novartis, Roche, and Servier and receiving consulting fees from AbbVie, Array, Astellas, AstraZeneca, Bayer, Beigene, Biocartis, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Daiichi, Halozyme, GlaxoSmithKline, Helsinn, Incyte, Ipsen, Janssen Research, Lilly, Merck Sharp & Dohme, Merck KGaA, Mirati, Novartis, Pierre Fabre, Roche, Seattle Genetics, Servier, Sirtex, Terumo, Taiho, TRIGR, and Zymeworks. CW reports grants paid to the institution by Boston Biomedical, Bristol Myers Squibb, Lycera, RAPT Therapeutics, Seagen, Symphogan, Vaccinex, INHBRX, and Pfizer; receiving honoraria from Array Biopharma, Signatera, Pfizer, Daiichi Sankyo; receiving travel support from Array Biopharma; and former employment at Winship Cancer Institute of Emory University, Atlanta, GA, USA (at the time of study conduct). ASP reports receiving support for the present from Seagen to provide medical writing assistance, institutional funding, study materials, processing charges; funding paid to the institution for clinical research trials from Ipsen, Bristol Myers Squibb, Exelixis, HutchMed, Seagen, Taiho, Lilly, AstraZeneca, Incyte, Deciphera, G1 Therapeutics, Zentalis, Tempus, Camurus, Relay Therapeutics, Nucana, Merck, and Bayer; receiving honoraria from Ideo Oncology and MJH Life Sciences (both educational event companies); participating in advisory boards for Amgen, Bristol Myers Squibb, Eisai, Ipsen, AAA, Exelixis, Pfizer, QED, Lilly, Mirati, HutchMed, Astellas, and Aadi; receiving travel support from Pfizer; owning stock or stock options from Aptose, Actinium, and Alexion; and receiving medical writing services from Bayer, Ipsen, HutchMed, Exelixis, and Seagen. JMH reports grants paid to the institution by Merck, Boston Biomedical, Senhwa Pharmaceuticals, Bayer, Incyte, TriOncology, Seattle Genetics, Hutchison MediPharma, Pionyr Immunotherapeutics, Trovogene, G1 Therapeutics, Roche, and Treos Bio and participation on advisory boards with honoraria to the institution by Bayer, Merck, BeiGene, and Incyte. ALC reports grants from Nucana, Seagen, Abgenomics, Novocure, Actuate, Medimmune/AstraZeneca, PanCan, Amgen, and Nextrast. CF reports support for the present manuscript paid to the institution by Seattle Genetics (currently Seagen) and grants paid to their institution by the National Comprehensive Cancer Network Foundation, National Comprehensive Cancer Network Oncology Research Program, Taiho Oncology, National Cancer Institute (NCI), and Pfizer. AK reports no conflict of interest. PMK reports grants paid to the institution by Advanced Accelerator Applications, Tersera, and Boston Scientific; a consultancy and advisory board relationship with Elicio (scientific advisory board member/shares/stock ownership); receiving consulting fees from Natera, Foundation Medicine, Illumina, BostonGene, Merck/MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, IPBA, QED Therapeutics, Boston Healthcare Associates, Servier, Taiho Oncology, Exact Sciences, Daiichi Sankyo/AstraZeneca, Eisai, and Seattle Genetics; consulting fees paid to the institution by Taiho Pharmaceutical and Ipsen; receiving travel support from AstraZeneca; and former employment at University of Iowa Hospitals and Clinics, Iowa City, IA, USA (at the time of study conduct). H-JL reports grants from NCI (P30, U01, U2c, UG1, and UM1), US Department of Defense, Southwest Oncology Group; receiving consulting fees from Merck, Bayer, Merck KG, Roche, Fulgent, Oncocyte, G1 Therapeutics, Jazz Therapeutics, 3T bioscience, and Adagene; receiving honoraria from Bayer, Roche, and Pfizer; participating in unpaid leadership roles with Wunderglo Foundation, Debbie Dream Foundation, and Cancer Support Group; and owning stock options in Fulgent. KKC reports grants paid to the institution by Bristol Myers Squibb, Array, Incyte, Daiichi Sankyo, Nucana, Merck, Pfizer, Calithera, Genentech, and Seagen; participating on advisory boards and receiving consulting fees from Merck, Lilly/Loxo, Pfizer, Replimune, Personalis, Exelixis, and Array; receiving travel or hotel support for attending advisory board meeting from Array; and participating on the Board of Directors for Academic and Community Cancer Research United. EE reports grants, receiving consulting fees and payment for expert testimony, receiving honoraria, receiving travel support, and participating in advisory boards from Amgen, Bayer, Hoffmann-La Roche, Merck Serono, Sanofi, Pierre Fabre, MSD, Organon, Novartis, Servier and financial support for clinical trials or contracted research paid to the institution from Amgen Inc, Array Biopharma Inc, AstraZeneca Pharmaceuticals LP, BeiGene, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Debiopharm International SA, F Hoffmann-La Roche, Genentech, HalioDX SAS, Hutchison MediPharma International, Janssen-Cilag SA, MedImmune, Menarini, Merck Health KGAA, Merck Sharp & Dohme, Merus NV, Mirati, Novartis Farmaceutica SA, Pfizer, Pharma Mar, Sanofi Aventis Recherche & Developpement, Servier, Taiho Pharma USA. DLB reports a grant for trial support of the present study paid to the institution by Seagen; grants paid to the institution by Seagen, Rafael/Cornerstone, and Abbvie; receiving honoraria for speakers bureau from Natera; receiving salary support for participating on the local data safety monitoring board for University Hospitals; receiving no payment for participating on the advisory board for Rafael pharmaceuticals; and receiving study drug from Novartis and Epizyme. CC reports grants paid to the institution by Merck, Bayer, Servier, Amgen, and Roche; receiving honoraria from Roche, Amgen, Merck, MSD, Pierre Fabre, Servier, Bayer, and Nordic Pharma; receiving payment for expert testimony from Merck and Bayer; receiving travel support from Amgen; participating on advisory boards for Nordic Pharma, Amgen, MSD, Pierre Fabre, and Mirati. FS reports no conflict of interest. MS reports being employed by and owning stock in Seagen. WF reports being employed by and owning stock in Seagen. TSB-S reports research funding paid to the institution by Agios, Arys, Arcus, Atreca, Boston Biomedical, Bayer, Eisai, Celgene, Lilly, Ipsen, Clovis, Seattle Genetics, Genentech, Novartis, Mirati, Merus, Abgenomics, Incyte, Pfizer, and Bristol Myers Squibb; consulting fees paid to the institution by Ipsen, Arcus, Pfizer, Seattle Genetics, Bayer, Genentech, Incyte, Eisai, and Merck; receiving consulting fees from Stemline, AbbVie, Boehringer Ingelheim, Janssen, Daichii Sankyo, Natera, TreosBio, Celularity, Exact Science, Sobi, Beigene, Kanaph, Astra Zeneca, Deciphera, MJH Life Sciences, Aptitude Health, Illumina, and Foundation Medicine; participating on independent data monitoring committees or data safety monitoring boards for Fibrogen, Suzhou Kintor, AstraZeneca, Exelixis, Merck/Eisai, PanCan, and 1Globe; participating on scientific advisory boards for Imugene, Immuneering, Xilis, Replimune Artiva, and Sun Biopharma; receiving royalties from Uptodate; and inventions or patents—WO/2018/183488: HUMAN PD1 PEPTIDE VACCINES AND USES THEREOF (licensed to Imugene) and WO/2019/055687: METHODS AND COMPOSITIONS FOR THE TREATMENT OF CANCER CACHEXIA (licensed to Recursion)., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: Anal squamous cell carcinoma (SCCA) is an uncommon malignancy with a rising incidence that has a high cure rate in its early stages. There is an unmet need for a reliable method to monitor response to treatment and assist in surveillance. Circulating tumor DNA (ctDNA) testing has shown great promise in other solid tumors for monitoring disease progression and detecting relapse in real time. This study aimed to determine the feasibility and use of personalized and tumor-informed ctDNA testing in SCCA., Patients and Methods: We analyzed real-world data from 251 patients (817 plasma samples) with stages I-IV SCCA, collected between 11/5/19 and 5/31/22. The tumor genomic landscape and feasibility of ctDNA testing was examined for all patients. The prognostic value of longitudinal ctDNA testing was assessed in patients with clinical follow-up (N = 37)., Results: Whole-exome sequencing analysis revealed PIK3CA as the most commonly mutated gene, and no associations between mutations and stage. Anytime ctDNA positivity and higher ctDNA levels (MTM/mL) were associated with metastatic disease (P = .004). For 37 patients with clinical follow-up, median follow-up time was 21.0 months (range: 4.1-67.3) post-diagnosis. For patients with stages I-III disease, anytime ctDNA-positivity after definitive treatment was associated with reduced DFS (HR: 28.0; P = .005)., Conclusions: Our study demonstrates the feasibility of personalized and tumor-informed ctDNA testing as an adjunctive tool in patients with SCCA as well as potential use for detection of molecular/minuteimal residual disease, and relapse during surveillance. Prospective studies are needed to better evaluate the use of ctDNA testing in this indication., (© The Author(s) 2022. Published by Oxford University Press.)

Merkel cell carcinoma is a rare, aggressive skin malignancy, also known as neuroendocrine carcinoma of the skin, with high rates of recurrence and distant metastasis. In refractory metastatic Merkel cell carcinoma (mMCC), besides immunotherapy, chemotherapy, and radiation, peptide receptor radionuclide therapy (PRRT) may be a viable option since this type of tumor can express somatostatin receptors. Methods: We performed a comprehensive review of the literature to evaluate the efficacy of PRRT in mMCC patients. Results: Thirty-seven patients with mMCC received PRRT (1-5 cycles) with 177 Lu- or 90 Y-labeled somatostatin analogs (cumulative activity, 1.5-30 GBq). Radiographic response was available for 19 of 28 patients who received PRRT alone. Six (31.6%) of 19 patients showed objective responses, from partial to complete, and no severe adverse events were reported. Conclusion: Our analysis supports the use of PRRT in mMCC with sufficient somatostatin receptor uptake, although the quality of the available evidence is low. Prospective clinical trials are already in development and have started accruing in some parts of the world., (© 2023 by the Society of Nuclear Medicine and Molecular Imaging.)

Acquired resistance to systemic treatments is inevitable in most cancers, but the genetic basis for this in many cancer types has remained elusive due to constraints in obtaining tissue specimens longitudinally. In the management of gastrointestinal cancers, molecular profiling is conventionally performed at a single time point, although serial evaluations may yield biological insights that inform treatment decisions. We characterize genetic changes in serial liquid biopsies which provide real-time snapshots of tumor genetics and heterogeneity in refractory non-colorectal gastrointestinal cancers, and determine the clinical utility of repeat circulating tumor DNA (ctDNA) testing. In a national cohort of 449 patients with pancreatic, biliary, esophagogastric, and hepatocellular cancers, resistance to conventional therapies is broadly associated with tumor evolution. Emergent ctDNA alterations only detectable at progression occurs in 63% of patients and are frequently associated with treatment actionability. Tumor mutation burden is dynamic in cancers undergoing treatment, but is not associated with time to progression. Objective tumor responses in a case series of patients receiving treatment matched to emergent alterations show that repeat liquid biopsies may have clinical benefit by expanding treatment options in advanced gastrointestinal cancers., (© 2022. The Author(s).)

Purpose: Circulating tumor DNA (ctDNA) analyses allow for postoperative risk stratification in patients with curatively treated colon and breast cancers. Use of ctDNA in esophagogastric cancers (EGC) is less characterized and could identify high-risk patients who have been treated with curative intent., Methods: In this retrospective analysis of real-world data, ctDNA levels were analyzed in the preoperative, postoperative, and surveillance settings in patients with EGC using a personalized multiplex polymerase chain reaction-based next-generation sequencing assay. Plasma samples (n = 943) from 295 patients at > 70 institutions were collected before surgery, postoperatively, and/or serially during routine clinical follow-up from September 19, 2019, to February 21, 2022. ctDNA detection was annotated to clinicopathologic features and recurrence-free survival., Results: A total of 295 patients with EGC were analyzed, and 212 patients with stages I-III disease were further explored. Pretreatment ctDNA was detected in 96% (23/24) of patients with preoperative time points. Postoperative ctDNA was detected in 23.5% (16/68) of patients with stage I-III EGC within 16 weeks (molecular residual disease window) after surgery without receiving systemic therapy. ctDNA detection at any time point after surgery (hazard ratio [HR], 23.6; 95% CI, 10.2 to 66.0; P < .0001), within the molecular residual disease window (HR, 10.7; 95% CI, 4.3 to 29.3; P < .0001), and during the surveillance period (HR, 17.7; 95% CI, 7.3 to 50.7; P < .0001) was associated with shorter recurrence-free survival. In multivariable analysis, ctDNA status and clinical stage of disease were independently associated with outcomes., Conclusion: Using real-world data, we demonstrate that postoperative tumor-informed ctDNA detection in EGC is feasible and allows for enhanced patient risk stratification and prognostication during curative-intent therapy., Competing Interests: Brandon M. HuffmanStock and Other Ownership Interests: Doximity Vasily N. AushevEmployment: NateraStock and Other Ownership Interests: NateraTravel, Accommodations, Expenses: Natera Griffin L. BuddeEmployment: NateraStock and Other Ownership Interests: NateraTravel, Accommodations, Expenses: Natera Joseph ChaoConsulting or Advisory Role: Lilly, Merck, AstraZeneca, Foundation Medicine, Daiichi Sankyo, Amgen, Bristol Myers Squibb, Astellas Pharma, Turning Point Therapeutics, Roche, Silverback Therapeutics, Novartis, Coherus Biosciences, Geneos, Guardant HealthSpeakers' Bureau: Merck, Bristol Myers SquibbResearch Funding: Merck (Inst), Novonco Therapeutics (Inst), Brooklyn Immunotherapeutics (Inst)Travel, Accommodations, Expenses: Merck, Macrogenics, Foundation Medicine, AmgenOther Relationship: Yiviva Farshid DayyaniEmployment: RocheConsulting or Advisory Role: Genentech/Roche, Array BioPharma, Exelixis, Eisai, QED Therapeutics, SignateraSpeakers' Bureau: Genentech/Roche, Amgen, Eisai, ipsen, Exelixis, Sirtex Medical, Deciphera, Natera, ServierResearch Funding: Bristol Myers Squibb (Inst), AstraZeneca (Inst), Merck (Inst), Genentech (Inst), Taiho Pharmaceutical (Inst), Exelixis (Inst), Ipsen (Inst) Diana HannaConsulting or Advisory Role: Boehringer Ingelheim, AstraZeneca Gregory P. BottaHonoraria: NateraConsulting or Advisory Role: NateraSpeakers' Bureau: Natera Daniel V.T. CatenacciHonoraria: Genentech/Roche, Lilly, Amgen, Foundation Medicine, Taiho Pharmaceutical, Guardant Health, Merck, Bristol Myers Squibb, Gritstone Bio, Five Prime Therapeutics, Astellas Pharma, Seattle Genetics, Tempus, Pieris Pharmaceuticals, Daiichi Sankyo/UCB Japan, Zymeworks, QED Therapeutics, Natera, Archer, NovartisConsulting or Advisory Role: Genentech/Roche, Amgen, Merck, Lilly, Taiho Pharmaceutical, Bristol Myers Squibb, Astellas Pharma, Seattle Genetics, Daiichi Sankyo/UCB Japan, Zymeworks, Guardant HealthSpeakers' Bureau: Guardant Health, Genentech, Lilly, Merck, Tempus, Daiichi Sankyo/Astra Zeneca Steven B. MaronStock and Other Ownership Interests: Calithera BiosciencesHonoraria: Vindico Medical Education, Clarion Healthcare, Physicans' Education ResourceConsulting or Advisory Role: Natera, Basilea, Daichi Sankyo, Bicara Therapeutics, Novartis, AmgenResearch Funding: Guardant Health (Inst), Epic Sciences Shifra KrinshpunEmployment: NateraStock and Other Ownership Interests: NateraTravel, Accommodations, Expenses: Natera Shruti SharmaEmployment: NateraStock and Other Ownership Interests: Natera Giby V. GeorgeEmployment: NateraStock and Other Ownership Interests: Natera Meenakshi MalhotraEmployment: NateraStock and Other Ownership Interests: Natera Adham JurdiEmployment: NateraStock and Other Ownership Interests: Natera, Cardiff OncologySpeakers' Bureau: NateraTravel, Accommodations, Expenses: Natera Solomon MoshkevichEmployment: Natera, Mahana TherapeuticsStock and Other Ownership Interests: NateraPatents, Royalties, Other Intellectual Property: Named as inventor on a patent filed by Natera, incTravel, Accommodations, Expenses: Natera Alexey AleshinEmployment: Natera, NateraLeadership: NateraStock and Other Ownership Interests: NateraConsulting or Advisory Role: Mission BioTravel, Accommodations, Expenses: Natera Pashtoon M. KasiConsulting or Advisory Role: Taiho Pharmaceutical (Inst), Ipsen (Inst), Natera, Foundation Medicine, MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, Inflecton Point Biomedical Advisors, QED Therapeutics, Boston Healthcare Associates, SERVIER, Taiho Oncology, Exact Sciences, Daiichi Sankyo/Astra Zeneca, Eisai, Seattle GeneticsResearch Funding: Advanced Accelerator Applications (Inst), Tersera (Inst), Boston Scientific (Inst)Travel, Accommodations, Expenses: AstraZeneca Samuel J. KlempnerThis author is a member of the JCO Precision Oncology Editorial Board. Journal policy recused the author from having any role in the peer review of this manuscript.Stock and Other Ownership Interests: TP Therapeutics, Nuvalent, IncHonoraria: NateraConsulting or Advisory Role: Lilly, Astellas Pharma, Bristol Myers Squibb, Pieris Pharmaceuticals, Merck, Daiichi Sankyo/UCB Japan, Sanofi/Aventis, Mersana, Exact Sciences, NovartisResearch Funding: Leap Therapeutics (Inst), BeiGene (Inst), Silverback Therapeutics (Inst)Other Relationship: NCCNNo other potential conflicts of interest were reported.

There exists a tremendous opportunity in identifying and determining the appropriate predictive and prognostic biomarker(s) for risk stratification of patients with colorectal cancers (CRCs). Circulating tumor DNA (ctDNA) has emerged as a promising prognostic and possibly predictive biomarker in the personalized management of patients with CRCs. The disease is particularly suited to a liquid biopsy-based approach since there is a great deal of shedding of circulating tumor fragments (cells, DNA, methylation markers, etc). ctDNA has been shown to have several potential applications, including detecting minimal residual disease (MRD), monitoring for early recurrence, molecular profiling, and therapeutic response prediction. The utility of ctDNA has broadened from its initial use in the advanced/metastatic setting for molecular profiling and detection of acquired resistance mechanisms, toward identifying MRD, as well as early detection. Prospective studies such as CIRCULATE, COBRA, Dynamic II/III, and ACT3 are underway in the MRD setting to further understand how ctDNA may be used to inform clinical decision making using both tumor-informed and tumor-agnostic platforms. These prospective studies use ctDNA to guide management of patients with CRC and will be critical to help guide how and where ctDNA should or should not be used in clinical decision making. It is also important to understand that there are different types of ctDNA liquid biopsy platforms, each with advantages and disadvantages in different clinical indications. This review provides an overview of the current and evolving use of ctDNA in CRC.

Purpose: Subset analyses from phase III evaluation of epidermal growth factor receptor inhibition (EGFRi) suggest improved outcomes in patients with EGFR- amplified gastroesophageal adenocarcinoma (GEA), but large-scale analyses are lacking. This multi-institutional analysis sought to determine the role of EGFRi in the largest cohort of patients with EGFR- amplified GEA to date., Patients and Methods: A total of 60 patients from 15 tertiary cancer centers in six countries met the inclusion criteria. These criteria required histologically confirmed GEA in the metastatic or unresectable setting with EGFR amplification identified by using a Clinical Laboratory Improvement Amendments-approved assay, and who received on- or off-protocol EGFRi. Testing could be by tissue next-generation sequencing, plasma circulating tumor DNA next-generation sequencing, and/or fluorescence in situ hybridization performed by a Clinical Laboratory Improvement Amendments approved laboratory. Treatment patterns and outcomes analysis was also performed using a deidentified clinicogenomic database (CGDB)., Results: Sixty patients with EGFR -amplified GEA received EGFRi, including 31 of 60 patients (52%) with concurrent chemotherapy. Across treatment lines, patients achieved a 43% objective response rate with a median progression-free survival of 4.6 months (95% CI, 3.5 to 6.4). Patients receiving EGFRi in first-, second-, and third-line therapy achieved a median overall survival of 20.6 months (95% CI, 13.5 to not reached [NR]), 9 months (95% CI, 7.9 to NR), and 8.4 months (7.6 to NR), respectively. This survival far exceeded the 11.2-month (95% CI, 8.7 to 14.2) median overall survival from first-line initiation of non-EGFRi therapy in patients with EGFR -amplified GEA in the CGDB. Despite this benefit, analysis of the CGDB (January 2011-December 2020) suggests that only 5% of patients with EGFR -amplified GEA received EGFRi., Conclusion: Patients with EGFR- amplified GEA derive significant benefit from EGFRi. Further prospective investigation of EGFRi in a well-selected patient population is ongoing in an upcoming trial of amivantamab in EGFR and/or MET amplified GEA.

For patients with metastatic RAS/RAF wild-type refractory colorectal cancer, the question of anti-EGFR therapy rechallenge often comes up after initial use. However, not all patients derive benefit. It is now well known that these tumors acquire mechanisms of resistance in the mitogen-activated protein kinase (MAPK) pathway, which can be detected on circulating tumor DNA (ctDNA)-based testing. We present a series of patients who had serial testing post-EGFR blockade showing its feasibility and value. This would have implications for EGFR rechallenge. We reviewed records for patients who were initially noted to be RAS/RAF wild-type on tissue, who received prior anti-EGFR therapy and then subsequently had at least one circulating tumor DNA-based testing. These patients also had tissue-based genomic testing obtained earlier as part of their standard of care, alongside serial ctDNA-based testing that was done later when subsequent lines of therapy were being decided. The median duration of initial prior anti-EGFR therapy was around 10 months. Known acquired mechanisms of resistance were noted in 100% of the cases. These included KRAS , NRAS , extracellular domain mutations in EGFR , and BRAF mutations. Interestingly, the levels of the sub-clones expressed in variant allele fraction percentage varied and decreased over time in relation to timing of the prior EGFR exposure. Additionally, these were noted to be polyclonal, and the number of clones also varied including some disappearing over time during non-EGFR-based therapy (EGFR holiday). Patients' post-EGFR blockade may have multiple mechanisms of acquired resistance that can be easily detected on non-invasive liquid biopsies. These patients do not benefit from EGFR rechallenge based on the results of the recently reported CRICKET (NCT02296203) and CAVE (NCT04561336) clinical trials. Furthermore, excluding these patients from EGFR rechallenge is already being adopted in prospectively done clinical trials, e.g., the CHRONOS study (NCT03227926). Rechecking the liquid biopsy plasma RAS/RAF status is one thing that may be incorporated into practice with EGFR rechallenge only a consideration if acquired mechanisms of resistance are absent., Competing Interests: Author PMK: Consulting/Advisory Board: Merck/MSD, Servier, Delcath, Foundation Medicine, Taiho (self/institution), Tempus, QED, Eli Lilly, Daiiche Sankyo, Bayer, Incyte, Eisai, Natera, Exact Sciences, Ipsen (institution). Research support to institution: BTG/Boston Scientific, AstraZeneca, Tersera, RenovoRX. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Chennamadhavuni and Kasi.)

Clinical trials reporting the robust antitumor activity of immune checkpoint inhibitors (ICIs) in microsatellite instability-high (MSI-H) solid tumors have used tissue-based testing to determine the MSI-H status. This study assessed if MSI-H detected by a plasma-based circulating tumor DNA liquid biopsy test predicts robust response to ICI in patients with pancreatic ductal adenocarcinoma (PDAC). Retrospective analysis of patients with PDAC and MSI-H identified on Guardant360 from October 2018 to April 2021 was performed; clinical outcomes were submitted by treating providers. From 52 patients with PDAC +MSI-H, outcomes were available for 10 (19%) with a median age of 68 years (range: 56-82 years); the majority were male (80%) and had metastatic disease (80%). Nine of 10 patients were treated with ICI. Eight out of nine patients received single-agent pembrolizumab (8/9), while one received ipilimumab plus nivolumab. The overall response rate by Response Evaluation Criteria in Solid Tumors was 77% (7/9). The median progression-free survival and overall survival were not reached in this cohort. The median duration of treatment with ICI was 8 months (range: 1-24), and six out of seven responders continued to show response at the time of data cut-off after a median follow-up of 21 months (range: 11-33). Tissue-based MSI results were concordant with plasma-based G360 results in five of six patients (83%) who had tissue-based test results available, with G360 identifying one more patient with MSI-H than tissue testing. These results suggest that detecting MSI-H by a well-validated liquid biopsy test could predict a robust response to ICI in patients with PDAC. The use of liquid biopsy may expand the identification of PDAC patients with MSI-H tumors and enable treatment with ICI resulting in improved outcomes., Competing Interests: Competing interests: SC: Advisory role- QED Therapeutics. Research support-Natera. Speakers Bureau- Natera. LB :Employee and shareholder of Guardant Health, Inc. HD: Employee and shareholder of Guardant Health, Inc.PMK: Consulting or Advisory Role- Taiho Pharmaceutical (Inst), Ipsen (Inst), Natera, Foundation Medicine, AstraZeneca, MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, Axiom Healthcare Strategies, IPBA, QED Therapeutics, Boston Healthcare Associates. Research Funding- Bristol Myers Squibb (Inst), Advanced Accelerator Applications (Inst), Array BioPharma (Inst), Celgene (Inst), Tersera (Inst), Boston Scientific (Inst).Travel, Accommodations, Expenses- AstraZeneca., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: Immunotherapy (IO) has transformed the treatment paradigm for a wide variety of solid tumours. However, assessment of response can be challenging with conventional radiological imaging (eg, iRECIST), which do not precisely capture the unique response patterns of tumours treated with IO. Emerging data suggest that circulating tumour DNA (ctDNA) can aid in response assessment in patients with solid tumours receiving IO. The short half-life of ctDNA puts it in a unique position for early treatment response monitoring. The BESPOKE IO study is designed to investigate the clinical utility of serial ctDNA testing to assess treatment response using a tumour-informed, bespoke ctDNA assay (Signatera) and to determine its impact on clinical decision-making with respect to continuation/discontinuation, or escalation/de-escalation of immunotherapy in patients with advanced solid tumours., Methods and Analysis: The BESPOKE IO is a multicentre, prospective, observational study with a goal to enroll over 1500 patients with solid tumours receiving IO in up to 100 US sites. Patients will be followed for up to 2 years with serial ctDNA analysis, timed with every other treatment cycle. The primary endpoint is to determine the percentage of patients who will have their treatment regimen changed as guided by post-treatment bespoke ctDNA results along with standard response assessment tools. The major secondary endpoints include progression-free survival, overall survival and overall response rate based on the ctDNA dynamics., Ethics and Dissemination: The BESPOKE IO study was approved by the WCG Institutional Review Board (Natera-20-043-NCP BESPOKE Study of ctDNA Guided Immunotherapy (BESPOKE IO)) on 22 February 2021. Data protection and privacy regulations will be strictly observed in the capturing, forwarding, processing and storing patients' data. Natera will approve the publication of any study results in accordance with the site-specific contract., Trial Registration Number: NCT04761783., Competing Interests: Competing interests: PMK acknowledges role as a consultant/advisor for Taiho Oncology, Ipsen, Natera, Foundation Medicine, Research/Trial Support (to institution): BMS, Celgene, AstraZeneca, BTG, Advanced Accelerator Applications, Array Biopharma. SC acknowledges membership of the Natera’s speakers’ bureau. AP acknowledges membership of the Bristol Myers Squibb speakers’ bureau, role as a consultant for Novartis, participatory role in a Natera Ad Board, and role as a speaker for Natera and Grail. GA has nothing to disclose. LG is a federal employee and reports no conflict of interest. ZE: Research Support: Pfizer, Novartis; Consultancy: Pfizer, Eisai, Natera Inc., OncoSec, Genentech. All other authors are employees of Natera, Inc. with stock/options to own stock on the company. This study is being sponsored by Natera, Inc., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The practice of medicine has steadily employed less invasive methods to obtain information derived from the tumor to guide clinical management of patients. Liquid biopsy-the sampling of blood-is a non-invasive method for generating information previously only available from tissue biopsies of the tumor mass. Analysis of fragmented circulating tumor DNA in the plasma is clinically used to identify actionable mutations and detect residual or recurrent disease. Plasma analysis cannot, however, assess cancer phenotypes, including the expression of drug targets and protein biomarkers. Circulating tumor cells (CTCs) are intact cancer cells that have entered the blood that have the potential for distant metastasis. While enumeration of CTCs is prognostic of outcome, recently developed technology allows for the interrogation of protein biomarkers on CTCs that could be predictive of response. Furthermore, since CTCs contain intact whole cancer genomes, isolating viable CTCs detected during therapy could provide a rational approach to assessing mutational profiles of resistance. Identification, characterization and molecular analysis of CTCs together will advance the capacity of liquid biopsy to meet the requirements of twenty-first century medicine., Competing Interests: EK, AR, LC, NE and TG: employees of RareCyte, Inc. PK: Consulting/Advisory Board for AstraZeneca/Daiichi Sankyo, Axiom Healthcare Strategies, Bayer, Delcath Systems, Foundation Medicine, Incyte, Ipsen, IPBA, Lilly, Merck, MSD Oncology, Natera, Servier, Taiho Oncology, and Tempus; Research/Trial funding: BTG/Boston Scientific, Tersera, Merck. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Kaldjian, Ramirez, Costandy, Ericson, Malkawi, George and Kasi.)

Purpose: Earlier detection of cancer recurrence using circulating tumor DNA (ctDNA) to detect molecular residual disease (MRD) has the potential to dramatically affect cancer management. We review evidence supporting the use of ctDNA as a biomarker for detection of MRD and highlight the potential impact that ctDNA testing could have on the conduct of clinical trials., Methods: We searched the literature using MEDLINE (via PubMed) for articles from January 1, 2000, focusing on studies that assessed ctDNA as a predictor of cancer recurrence. Broadly focused searches on ctDNA and cancer were also performed to provide additional background information. www.clinialtrials.gov was searched to identify trials that incorporate ctDNA testing., Results: Numerous studies across different cancer types indicate that ctDNA-based MRD detection predicts recurrence with high sensitivity and specificity, and with lead times that precede standard imaging by up to 12 months. Recently, ctDNA testing has started being used to enroll MRD-positive patients at high risk of recurrence into trials, promising gains in statistical power that allow clinical utility to be demonstrated with smaller cohorts. Trials where ctDNA testing based-MRD detection is used to stratify patients into low or high-risk categories for treatment assignment are also ongoing. In addition, there is increasing evidence supporting the use of ctDNA dynamics or clearance as a surrogate end point, which could significantly reduce trial duration., Conclusion: ctDNA-based trial enrichment across many cancers seems likely to become increasingly common for cost- and time-reduction benefits. Trial efficiency could also benefit from using ctDNA as a surrogate end point, leading to accelerated approval of new therapeutics. A clear demonstration of efficacy from trials that use ctDNA-based MRD detection to assign treatment could transform clinical practice., Competing Interests: Pashtoon M. KasiConsulting or Advisory Role: Taiho Pharmaceutical (Inst), Ipsen (Inst), Natera, Foundation Medicine, AstraZeneca, MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, Axiom Healthcare Strategies, Inflecton Point Biomedical Advisors, QED Therapeutics, Boston Healthcare AssociatesResearch Funding: Bristol Myers Squibb (Inst), Advanced Accelerator Applications (Inst), Array BioPharma (Inst), Celgene (Inst), Tersera (Inst), Boston Scientific (Inst)Travel, Accommodations, Expenses: AstraZeneca Gordon FehringerEmployment: NateraStock and Other Ownership Interests: NateraConsulting or Advisory Role: Natera Hiroya TaniguchiHonoraria: Bayer, Sanofi, Takeda, Chugai Pharma, Taiho Pharmaceutical, Lilly Japan, Merck Serono, Yakult Honsha, Medical & Biological Laboratories Co, Ltd, Bristol Myers Squibb Japan, MSD K.K, Novartis, Daiichi Sankyo, Mitsubishi Tanabe Pharma, Nippon Kayaku, Ono YakuhinResearch Funding: Dainippon Sumitomo Pharma (Inst), Array BioPharma (Inst), MSD Oncology (Inst), Ono Pharmaceutical (Inst), Daiichi Sankyo (Inst), Sysmex (Inst), Novartis (Inst), Takeda (Inst) Naureen StarlingHonoraria: Lilly, MSD Oncology, Merck Serono, Pierre Fabre, SERVIER, GlaxoSmithKline, Amgen, NovartisConsulting or Advisory Role: SERVIER, AstraZeneca, Pfizer, MSD, Novartis Pharmaceuticals UK Ltd, MSD OncologyResearch Funding: AstraZeneca (Inst), Pfizer/EMD Serono (Inst), BMS (Inst)Travel, Accommodations, Expenses: MSD Oncology, AstraZeneca, BMS, Lilly, Merck, Roche Yoshiaki NakamuraResearch Funding: Taiho Pharmaceutical (Inst), Guardant Health (Inst), Genomedia (Inst), Chugai Pharma (Inst), Seattle Genetics (Inst), Roche Diagnostics Japan (Inst) Daisuke KotaniHonoraria: Takeda, Chugai Pharma, Lilly Japan, Merck Serono, Sysmex, Taiho Pharmaceutical, Ono Pharmaceutical, Bristol Myers Squibb Japan, MSD, Daiichi Sankyo/UCB JapanResearch Funding: Ono Pharmaceutical (Inst), MSD (Inst), Novartis (Inst), Janssen (Inst), IQvia (Inst), Syneos Health (Inst), CMIC (Inst) Thomas PowlesConsulting or Advisory Role: Bristol Myers Squibb, Merck, AstraZeneca, Ipsen, Pfizer, Novartis, Incyte, Seattle Genetics, Roche, Exelixis, MSD, Merck Serono, Astellas Pharma, Johnson & Johnson, EisaiResearch Funding: AstraZeneca, Roche, Bristol Myers Squibb, Exelixis, Ipsen, Merck, MSD, Novartis, Pfizer, Seattle Genetics, Merck Serono, Astellas Pharma, Johnson & Johnson, EisaiTravel, Accommodations, Expenses: Pfizer, MSD, AstraZeneca, Roche, Ipsen Bob T. LiResearch Funding: Roche/Genentech (Inst), AstraZeneca (Inst), GRAIL (Inst), Daiichi Sankyo (Inst), Hengrui Therapeutics (Inst), Guardant Health (Inst), Amgen (Inst), Lilly (Inst), MORE Health (Inst), Bolt Biotherapeutics (Inst).Patents, Royalties, Other Intellectual Property: US62/514,661 (Inst), US62/685,057 (Inst), Karger Publishers - Book royalty, Shanghai Jiao Tong University Press - Book royaltyTravel, Accommodations, Expenses: MORE Health, Jiangsu Hengrui MedicineUncompensated Relationships: Amgen, AstraZeneca, Genentech, Lilly, Boehringer Ingelheim, Daiichi Sankyo Lajos PusztaiHonoraria: bioTheranostics, Natera, OncoCyte, AthenexConsulting or Advisory Role: H3 Biomedicine, Merck, Novartis, Seattle Genetics, Syndax, AstraZeneca, Roche/Genentech, Bristol Myers Squibb, Clovis Oncology, Immunomedics, Eisai, Almac Diagnostics, PfizerResearch Funding: Merck (Inst), Genentech (Inst), Seattle Genetics (Inst), AstraZeneca (Inst), Bristol Myers Squibb (Inst), Pfizer (Inst)Travel, Accommodations, Expenses: AstraZenecaUncompensated Relationships: NanoString Technologies, Foundation MedicineOpen Payments Link: https://openpaymentsdata.cms.gov/physician/110878 Vasily N. AushevEmployment: NateraStock and Other Ownership Interests: NateraTravel, Accommodations, Expenses: Natera Ekaterina KalashnikovaEmployment: NateraStock and Other Ownership Interests: NateraTravel, Accommodations, Expenses: Natera Shruti SharmaEmployment: NateraStock and Other Ownership Interests: Natera Meenakshi MalhotraEmployment: NateraStock and Other Ownership Interests: Natera Zachary P. DemkoEmployment: NateraStock and Other Ownership Interests: Natera Alexey AleshinEmployment: NateraLeadership: NateraStock and Other Ownership Interests: NateraConsulting or Advisory Role: Mission BioTravel, Accommodations, Expenses: Natera Angel RodriguezEmployment: NateraLeadership: NateraStock and Other Ownership Interests: Natera Paul R. BillingsEmployment: NateraLeadership: Biological Dynamics, OmniSeq, Alveo Technologies, Mission BioStock and Other Ownership Interests: Natera, Trovagene, Biological Dynamics, OmniSeq, Alveo TechnologiesConsulting or Advisory Role: Bethesda Group, Guidepoint Global Axel GrotheyHonoraria: Elsevier, Aptitude Health, IMEDEXConsulting or Advisory Role: Genentech/Roche, Bayer (Inst), Bristol Myers Squibb (Inst), Lilly (Inst), Boston Biomedical (Inst), Amgen (Inst), Array BioPharma (Inst), Daiichi Sankyo (Inst), OBI PharmaResearch Funding: Genentech/Roche (Inst), Bayer (Inst), Pfizer (Inst), Eisai (Inst), Lilly (Inst), Boston Biomedical (Inst), Daiichi Sankyo (Inst), Array BioPharma (Inst).Travel, Accommodations, Expenses: Genentech/Roche, Bayer Julien TaiebConsulting or Advisory Role: Roche, Merck KGaA, Amgen, SERVIER, MSD, Pierre Fabre, NovartisSpeakers' Bureau: SERVIER, Amgen, Roche/Genentech, Sanofi, Merck, Lilly, MSD, Pierre Fabre David CunninghamStock and Other Ownership Interests: OVIBIOConsulting or Advisory Role: OVIBIOResearch Funding: Celgene (Inst), MedImmune (Inst), Bayer (Inst), 4SC (Inst), Clovis Oncology (Inst), Lilly (Inst), Roche (Inst), Leap Oncology (Inst). Takayuki YoshinoHonoraria: Chugai Pharma, Merck, Bayer Yakuhin, Ono Pharmaceutical, Lilly, Taiho PharmaceuticalResearch Funding: Chugai Pharma (Inst), MSD (Inst), DAIICHI SANKYO COMPANY, LIMITED (Inst), PAREXEL International Inc (Inst), Ono Pharmaceutical (Inst), Taiho Pharmaceutical (Inst), Amgen (Inst), Sanofi (Inst). Scott KopetzThis author is a member of the JCO Precision Oncology Editorial Board. Journal policy recused the author from having any role in the peer review of this manuscript.Stock and Other Ownership Interests: MolecularMatch, Lutris, Iylon, Frontier MedicinesConsulting or Advisory Role: Genentech, EMD Serono, Merck, Holy Stone Healthcare, Novartis, Lilly, Boehringer Ingelheim, Boston Biomedical, AstraZeneca/MedImmune, Bayer Health, Pierre Fabre, EMD Serono, Redx Pharma, Ipsen, Daiichi Sankyo, Natera, HalioDx, Lutris, Jacobio, Pfizer, Repare Therapeutics, Inivata, GlaxoSmithKline, Jazz Pharmaceuticals, Iylon, Xilis, AbbVie, Amal Therapeutics, Gilead Sciences, Mirati Therapeutics, Flame Biosciences, Servier, Carina Biotech, Bicara Therapeutics, Endeavor BioMedicines, Numab, Johnson & Johnson/Janssen, Genomic Health, Frontier MedicinesResearch Funding: Sanofi, Biocartis, Guardant Health, Array BioPharma, Genentech/Roche, EMD Serono, MedImmune, Novartis, Amgen, Lilly, Daiichi SankyoNo other potential conflicts of interest were reported.

Immune checkpoint inhibitors have shown great promise in treating patients with mismatch repair deficient/microsatellite instability high (dMMR/MSI-H) colorectal cancer (CRC). Although single-agent pembrolizumab has been approved for first-line treatment of dMMR/MSI-H metastatic CRC, combination therapy with cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) inhibition (ipilimumab/nivolumab) has reported higher response rates. It is unclear whether patients who progress on PD-1 inhibition will respond to CTLA-4 blockade. Here, we report a case series of three patients with dMMR/MSI-H mCRC, where a durable and ongoing response to nivolumab with ipilimumab was achieved after initial progression with pembrolizumab monotherapy. Blood-based biomarkers such as carcinoembryonic antigen and CA 19-9 were employed to assess treatment response and monitor disease progression along with circulating tumor DNA (ctDNA). Our findings indicate ctDNA's potential to accurately monitor response to therapy and detect disease progression, as validated by standard imaging. This case series demonstrates that CTLA-4 rescue is worthy of additional investigation as a treatment strategy after progression on PD-1 blockade in patients with dMMR/MSI-high mCRC. Our data support the utilization and expansion of clinical studies with combination therapies and using ctDNA kinetics as early dynamic marker for therapy response assessment., Competing Interests: Competing interests: PMK Consultancy/Advisory Board: Taiho Oncology, Ipsen, Natera, Foundation Medicine; Research/Trial Support (to institution): BMS, Celgene, AstraZeneca, BTG, Advanced Accelerator Applications, Array Biopharma. AG: Research funding from Array BioPharma, Bayer, Boston Biomedical, Daiichi Sankyo, Eisai, Genentech/Roche, Lilly, Pfizer. SEK: Research funding from Amgen, Array BioPharma, Biocartis, EMD Serono, Genentech/Roche, Guardant Health, Lilly, MedImmune, Novartis, Sanofi. GB, MK, VNA, AKM, MM, PO, PRB and AA are employees of Natera with stock/options to own stock in the company., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ.)

Competing Interests: Pashtoon Murtaza KasiConsulting or Advisory Role: Taiho Pharmaceutical (Inst), Ipsen (Inst), Natera, Foundation Medicine, AstraZeneca, MSD Oncology, Tempus, Bayer, Lilly, Delcath Systems, Axiom Healthcare Strategies, Inflection Point Biomedical Advisors, QED Therapeutics, Boston Healthcare AssociatesResearch Funding: Bristol Myers Squibb (Inst), Advanced Accelerator Applications (Inst), Array BioPharma (Inst), Celgene (Inst), TerSera (Inst), Boston Scientific (Inst)Travel, Accommodations, Expenses: AstraZenecaNo other potential conflicts of interest were reported.