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Introduction: Colorectal cancer (CRC) is a major public health problem. Despite major progress understanding the biological basis of this tumor added to the incorporation of optimized diagnostic an...

Purpose: OncoBEAM™ is a circulating tumor DNA (ctDNA) test that uses the BEAMing digital PCR technology. We clarified the association between the baseline tumor burden and discordance in the RAS status by metastatic sites in patients with a single metastatic site. Experimental Design: Data from previous Spanish and Japanese studies investigating the concordance of the RAS status between OncoBEAM™ and tissue biopsy in 221 patients with metastatic colorectal cancer (mCRC) were used. We collected data from patients with liver, peritoneal, or lung metastases and evaluated the concordance rates according to the metastatic site and the association between the concordance rate and tumor burden. Results: Patients had metastases in the liver (n = 151), peritoneum (n = 25), or lung (n = 45) with concordance rates of 91% (95% confidence interval, 85%–95%), 88% (68%–97%), and 64% (49%–78%), respectively. Factors associated with concordance included the baseline longest diameter and lesion number (P = 0.004), and sample collection interval (P = 0.036). Concordance rates ≥90% were observed in the following groups: liver metastases alone, regardless of the baseline longest diameter and lesion number; peritoneal metastases alone in patients with a baseline longest diameter ≥20 mm; and lung metastases alone in patients with a baseline longest diameter ≥20 mm and/or number of lesions ≥10. Conclusions: Plasma ctDNA-based liquid biopsy in patients with mCRC may be useful depending on the metastatic site. The maximum diameter and lesion number should be carefully considered when determining patients' RAS status with only peritoneal or lung metastases.

Summary Background Effective treatments for patients with cholangiocarcinoma after progression on gemcitabine-based chemotherapy are urgently needed. Mutations in the BRAF gene have been found in 5% of biliary tract tumours. The combination of dabrafenib and trametinib has shown activity in several BRAFV600E-mutated cancers. We aimed to assess the activity and safety of dabrafenib and trametinib combination therapy in patients with BRAFV600E-mutated biliary tract cancer. Methods This study is part of an ongoing, phase 2, open-label, single-arm, multicentre, Rare Oncology Agnostic Research (ROAR) basket trial in patients with BRAFV600E-mutated rare cancers. Patients were eligible for the biliary tract cancer cohort if they were aged 18 years or older, had BRAFV600E-mutated, unresectable, metastatic, locally advanced, or recurrent biliary tract cancer, an Eastern Cooperative Oncology Group performance status of 0–2, and had received previous systemic treatment. All patients were treated with oral dabrafenib 150 mg twice daily and oral trametinib 2 mg once daily until disease progression or intolerance of treatment. The primary endpoint was the overall response rate, which was determined by Response Evaluation Criteria in Solid Tumors version 1.1 in the intention-to-treat evaluable population, which comprised all enrolled patients regardless of receiving treatment who were evaluable (ie, had progression, began a new anticancer treatment, withdrew consent, died, had stable disease for 6 weeks or longer, or had two or more post-baseline assessments). The ROAR trial is registered with ClinicalTrials.gov , NCT02034110 . These results are based on an interim analysis; the study is active but not recruiting. Findings Between March 12, 2014, and July 18, 2018, 43 patients with BRAFV600E-mutated biliary tract cancer were enrolled to the study and were evaluable. Median follow-up was 10 months (IQR 6–15). An investigator-assessed overall response was achieved by 22 (51%, 95% CI 36–67) of 43 patients. An independent reviewer-assessed overall response was achieved by 20 (47%, 95% CI 31–62) of 43 patients. The most common grade 3 or worse adverse event was increased γ-glutamyltransferase in five (12%) patients. 17 (40%) patients had serious adverse events and nine (21%) had treatment-related serious adverse events, the most frequent of which was pyrexia (eight [19%]). No treatment-related deaths were reported. Interpretation Dabrafenib plus trametinib combination treatment showed promising activity in patients with BRAFV600E-mutated biliary tract cancer, with a manageable safety profile. Routine testing for BRAFV600E mutations should be considered in patients with biliary tract cancer. Funding GlaxoSmithKline and Novartis.

Background EGFR amplification occurs in about 1% of metastatic colorectal cancers (mCRCs) but is not routinely tested as a prognostic or predictive biomarker for patients treated with anti-EGFR monoclonal antibodies. Herein, we aimed to characterize the clinical and molecular landscape of EGFR-amplified mCRC. Methods In this multinational cohort study, we compared clinical data of 62 patients with EGFR-amplified vs 1459 EGFR nonamplified mCRC, as well as comprehensive genomic data of 35 EGFR-amplified vs 439 EGFR nonamplified RAS/BRAF wild-type and microsatellite stable (MSS) tumor samples. All statistical tests were 2-sided. Results EGFR amplification was statistically significantly associated with left primary tumor sidedness and RAS/BRAF wild-type status. All EGFR-amplified tumors were MSS and HER2 nonamplified. Overall, EGFR-amplified samples had higher median fraction of genome altered compared with EGFR-nonamplified, RAS/BRAF wild-type MSS cohort. Patients with EGFR-amplified tumors reported longer overall survival (OS) (median OS = 71.3 months, 95% confidence interval [CI] = 50.7 to not available [NA]) vs EGFR-nonamplified ones (24.0 months; 95% CI = 22.8 to 25.6; hazard ratio [HR] = 0.30, 95% CI = 0.20 to 0.44; P < .001; adjusted HR = 0.46, 95% CI = 0.30 to 0.69; P < .001). In the subgroup of patients with RAS/BRAF wild-type mCRC exposed to anti-EGFR-based therapy, EGFR amplification was again associated with better OS (median OS = 54.0 months, 95% CI = 35.2 to NA, vs 29.1 months, 95% CI = 27.0 to 31.9, respectively; HR = 0.46, 95% CI = 0.28 to 0.76; P = .002). Conclusion Patients with EGFR-amplified mCRC represent a biologically defined subgroup and merit dedicated clinical trials with novel and more potent EGFR-targeting strategies beyond single-agent monoclonal antibodies.

Immunotherapy; Phase 1 trials; Prognostic model Inmunoterapia; Ensayos de fase 1; Modelo pronóstico Immunoteràpia; Assajos de fase 1; Model pronòstic Purpose Patient selection in phase 1 clinical trials (Ph1t) continues to be a challenge. The aim of this study was to develop a user-friendly prognostic calculator for predicting overall survival (OS) outcomes in patients to be included in Ph1t with immune checkpoint inhibitors (ICIs) or targeted agents (TAs) based on clinical parameters assessed at baseline. Methods Using a training cohort with consecutive patients from the VHIO phase 1 unit, we constructed a prognostic model to predict median OS (mOS) as a primary endpoint and 3-month (3m) OS rate as a secondary endpoint. The model was validated in an internal cohort after temporal data splitting and represented as a web application. Results We recruited 799 patients (training and validation sets, 558 and 241, respectively). Median follow-up was 21.2 months (m), mOS was 10.2 m (95% CI, 9.3–12.7) for ICIs cohort and 7.7 m (95% CI, 6.6–8.6) for TAs cohort. In the multivariable analysis, six prognostic variables were independently associated with OS – ECOG, number of metastatic sites, presence of liver metastases, derived neutrophils/(leukocytes minus neutrophils) ratio [dNLR], albumin and lactate dehydrogenase (LDH) levels. The phase 1 prognostic online (PIPO) calculator showed adequate discrimination and calibration performance for OS, with C-statistics of 0.71 (95% CI 0.64–0.78) in the validation set. The overall accuracy of the model for 3m OS prediction was 87.2% (95% CI 85%–90%). Conclusions PIPO is a user-friendly objective and interactive tool to calculate specific survival probabilities for each patient before enrolment in a Ph1t. The tool is available at https://pipo.vhio.net/. The research leading to these results has received funding from “la Caixa” Foundation (LCF/PR/CE07/50610001). Cellex Foundation for providing research facilities and equipment. This work was supported by the Accelerator Award (UpSMART) from Fundacion Científica – Asociacion Espanola Contra el Cancer (FC -AECC)/ Associazione Italiana per la Ricerca sul Cancro (AIRC) /Cancer Research United Kingdom (CRUK).

Neoplasias gastrointestinales; Inmunoterapia Neoplàsies gastrointestinals; Immunoteràpia Gastrointestinal neoplasms; Immunotherapy Background The efficacy of immune checkpoint inhibitors (ICIs) in patients with microsatellite instability (MSI)-high metastatic colorectal cancer (mCRC) is unprecedented. A relevant proportion of subjects achieving durable disease control may be considered potentially ‘cured’, as opposed to patients experiencing primary ICI refractoriness or short-term clinical benefit. We developed and externally validated a nomogram to estimate the progression-free survival (PFS) and the time-independent event-free probability (EFP) in patients with MSI-high mCRC receiving ICIs. Methods The PFS and EFP were estimated using a cure model fitted on a developing set of 163 patients and validated on a set of 146 patients with MSI-high mCRC receiving anti-programmed death (ligand)1 (PD-(L)1) ± anticytotoxic T-lymphocyte antigen 4 (CTLA-4) agents. A total of 23 putative prognostic factors were chosen and then selected using a random survival forest (RSF). The model performance in estimating PFS probability was evaluated by assessing calibration (internally—developing set and externally—validating set) and quantifying the discriminative ability (Harrell C index). Results RFS selected five variables: ICI type (anti-PD-(L)1 monotherapy vs anti-CTLA-4 combo), ECOG PS (0 vs >0), neutrophil-to-lymphocyte ratio (≤3 vs >3), platelet count, and prior treatment lines. As both in the developing and validation series most PFS events occurred within 12 months, this was chosen as cut-point for PFS prediction. The combination of the selected variables allowed estimation of the 12-month PFS (focused on patients with low chance of being cured) and the EFP (focused on patients likely to be event-free at a certain point of their follow-up). ICI type was significantly associated with disease control, as patients receiving the anti-CTLA-4-combination experienced the best outcomes. The calibration of PFS predictions was good both in the developing and validating sets. The median value of the EFP (46%) allowed segregation of two prognostic groups in both the developing (PFS HR=3.73, 95% CI 2.25 to 6.18; p

BACKGROUND: Patients with metastatic colorectal cancer with the BRAF V600E mutation have a poor prognosis, with a median overall survival of 4 to 6 months after failure of initial therapy. Inhibition of BRAF alone has limited activity because of pathway reactivation through epidermal growth factor receptor signaling. METHODS: In this open-label, phase 3 trial, we enrolled 665 patients with BRAF V600E-mutated metastatic colorectal cancer who had had disease progression after one or two previous regimens. Patients were randomly assigned in a 1:1:1 ratio to receive encorafenib, binimetinib, and cetuximab (triplet-therapy group); encorafenib and cetuximab (doublet-therapy group); or the investigators' choice of either cetuximab and irinotecan or cetuximab and FOLFIRI (folinic acid, fluorouracil, and irinotecan) (control group). The primary end points were overall survival and objective response rate in the triplet-therapy group as compared with the control group. A secondary end point was overall survival in the doublet-therapy group as compared with the control group. We report here the results of a prespecified interim analysis. RESULTS: The median overall survival was 9.0 months in the triplet-therapy group and 5.4 months in the control group (hazard ratio for death, 0.52; 95% confidence interval [CI], 0.39 to 0.70; P

KRAS mutations are common in colorectal cancer (CRC). In this setting, mutation status determination in circulating-free DNA from blood samples (liquid biopsy) has been shown to be a viable alternative to tissue testing. The objective of this study was to compare the sensitivity of two liquid biopsy methods for detecting KRAS mutations in plasma samples from metastatic CRC patients. Samples with a positive (KRAS-MUT+) result and a mutant allelic fraction (MAF) KRAS mutations in 81/116 OncoBEAM KRAS-MUT+ samples with MAF KRAS mutations than Idylla. Importantly, our data identified a “gray zone” below 1% MAF where Idylla showed reduced KRAS mutation detection, highlighting the importance of an accurate method to provide the mutational status of CRC patients.

INTRODUCTION The addition of monoclonal antibody (mAb) epidermal growth factor receptor (EGFR) inhibitors to classic chemotherapy doublet backbones has improved survival of metastatic colorectal cancer (mCRC). However, the role of triple-drug chemotherapy regimens in combination with an anti-EGFR mAb inhibitor is not yet clear. AREAS COVERED The activity of triple-drug chemotherapy regimens when combined with an anti-EGFR mAb in mCRC patients is examined. We describe the overall safety and tolerability profiles based on a literature review of all published phase I and II clinical trials in this setting. Drug exposure, tumor mutational status, and metastases resectability are discussed. A review of PubMed and abstracts of major oncology congresses from 2009 to 2018, with MeSH and full-text search terms for clinical trials of anti-EGFR for 'metastatic' or 'advanced' 'colorectal cancer/adenocarcinoma' was implemented. Only English language publications were included. EXPERT OPINION Efficacy data from phase II trials are promising, but the safety profiles are not as encouraging; the development of severe diarrhea and acneiform rash limit the drug exposure that is critical for improved outcomes. Phase II studies of these triplet chemotherapy/anti-EGFR mAb combinations have focused on conversion therapy in liver-limited disease or in the first-line setting in advanced disease. The identification of biomarkers of response and toxicity may support the use of personalized medicine and more precise design of phase III trials.

Background Metastatic colorectal cancer (mCRC) has low survival rates. We assessed if addition of veliparib, concurrent to FOLFIRI, improves survival in patients with previously untreated mCRC. Methods This study compared veliparib (200 mg BID for 7 days of each 14-day cycle) to placebo, each with FOLFIRI. Bevacizumab was allowed in both arms. The primary endpoint was progression-free survival (PFS). Results Patients were randomised to receive veliparib (n = 65) or placebo (n = 65) in combination with FOLFIRI. Median PFS was 12 vs 11 months (veliparib vs placebo) [HR = 0.94 (95% CI: 0.60, 1.48)]. Median OS was 25 vs 27 months [HR = 1.26 (95% CI: 0.74, 2.16)]. Response rate was 57% vs 62%. Median DOR was 11 vs 9 months [HR = 0.73 (95% CI: 0.38, 1.40)]. AEs with significantly higher frequency (p

BACKGROUND: In the KEYNOTE-177 study, pembrolizumab monotherapy provided statistically significant and clinically meaningful improvements in progression-free survival versus chemotherapy as first-line treatment in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. To further support the efficacy and safety findings of the KEYNOTE-177 study, results of the health-related quality of life (HRQOL) analyses are reported here.METHODS: KEYNOTE-177 is an open-label, randomised, phase 3 trial being done at 192 cancer centres in 23 countries, in patients aged 18 years and older with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had not received previous systemic therapy for metastatic disease. Eligible patients were randomly assigned (1:1) centrally by use of interactive voice response or integrated web response technology to receive pembrolizumab 200 mg intravenously every 3 weeks or investigator's choice chemotherapy (mFOLFOX6 [leucovorin, fluorouracil, and oxaliplatin] or FOLFIRI [leucovorin, fluorouracil, and irinotecan] intravenously every 2 weeks with or without intravenous bevacizumab or cetuximab). Patients and investigators were not masked to treatment assignment. The primary endpoints were progression-free survival (previously reported) and overall survival (data to be reported at the time of the final analysis). HRQOL outcomes were evaluated as prespecified exploratory endpoints. The analysis population comprised all randomly assigned patients who received at least one dose of study treatment and completed at least one HRQOL assessment. HRQOL outcomes were mean change from baseline to prespecified week 18 in European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and EORTC Quality of Life Questionnaire-Colorectal 29 (EORTC QLQ-CR29) scale and item scores, and in the EuroQoL 5 Dimensions 3 Levels (EQ-5D-3L) visual analogue scale and health utility scores; the proportion of patients with improved, stable, or deteriorated scores from baseline to prespecified week 18 in EORTC QLQ-C30 scales and items; and time to deterioration in EORTC QLQ-C30 global health status/quality of life (GHS/QOL), physical functioning, social functioning, and fatigue scores and EORTC QLQ-CR29 urinary incontinence scores. The threshold for a small and clinically meaningful mean difference in EORTC QLQ-C30 score was 5-8 points. This study is registered with ClinicalTrials.gov, NCT02563002 and is ongoing; recruitment is closed.FINDINGS: Between Feb 11, 2016, and Feb 19, 2018, 307 patients were enrolled and randomly assigned to receive pembrolizumab (n=153) or chemotherapy (n=154). The HRQOL analysis population comprised 294 patients (152 receiving pembrolizumab and 142 receiving chemotherapy). As of Feb 19, 2020, median time from randomisation to data cutoff was 32·4 months (IQR 27·7-37·8). Least squares mean (LSM) change from baseline to prespecified week 18 showed a clinically meaningful improvement in EORTC QLQ-C30 GHS/QOL scores with pembrolizumab versus chemotherapy (between-group LSM difference 8·96 [95% CI 4·24-13·69]; two-sided nominal p=0·0002). Median time to deterioration was longer with pembrolizumab versus chemotherapy for GHS/QOL (hazard ratio 0·61 [95% CI 0·38-0·98]; one-sided nominal p=0·019), physical functioning (0·50 [95% CI 0·32-0·81]; one-sided nominal p=0·0016), social functioning (0·53 [95% CI 0·32-0·87]; one-sided nominal p=0·0050), and fatigue scores (0·48 [95% CI 0·33-0·69]; one-sided nominal pINTERPRETATION: Pembrolizumab monotherapy led to clinically meaningful improvements in HRQOL compared with chemotherapy in patients with previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. These data, along with the previously reported clinical benefits, support pembrolizumab as a first-line treatment option for this population.FUNDING: Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ, USA.

Simple Summary The survival of patients with metastatic colorectal cancer (mCRC) has been improved over the years and now reaches 30–40 months. However, few therapeutic options are available after failure of first- and second-line treatments. In fact, prognosis of chemo-refractory mCRC remains poor. Therefore, new therapeutic strategies are needed. Emerging evidence suggest that retreatment with epidermal growth factor (EGFR) inhibitors after a treatment break, in patients that obtained a clinical benefit by previous anti-EGFR, could lead to prolonged survival. The rationale beyond this “rechallenge” strategy is that after a “treatment holiday” EGFR resistant cancer cells decay, restoring the sensibility to EGFR blockade. In this review we analyze the current knowledge of retreatment with EGFR inhibitors, examine the role of novel biomarkers that can guide the appropriate selection of patients. Finally, we discuss future perspectives and on-going clinical trials. Abstract The prognosis of patients with metastatic colorectal cancer (mCRC) who progressed to the first and the second lines of treatment is poor. Thus, new therapeutic strategies are needed. During the last years, emerging evidence suggests that retreatment with anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MAbs) in the third line of mCRC patients, that have previously obtained clinical benefit by first-line therapy with anti-EGFR MAbs plus chemotherapy, could lead to prolonged survival. The rationale beyond this “rechallenge” strategy is that, after disease progression to first line EGFR-based therapy, a treatment break from anti-EGFR drugs results in RAS mutant cancer cell decay, restoring the sensitivity of cancer cells to cetuximab and panitumumab. In fact, rechallenge treatment with anti-EGFR drugs has shown promising clinical activity, particularly in patients with plasma RAS and BRAF wild type circulating tumor DNA, as defined by liquid biopsy analysis at baseline treatment. The aim of this review is to analyze the current knowledge on rechallenge and to investigate the role of novel biomarkers that can guide the appropriate selection of patients that could benefit from this therapeutic strategy. Finally, we discuss on-going trials and future perspectives.

Background: The ESMO Resilience Task Force has investigated wellbeing since COVID-19 in relation to work, lifestyle and support factors in oncology professionals globally. We reported on the significant impact of the initial surge of the pandemic on wellbeing and job performance (Banerjee et al. 2021). As the pandemic continues, it is imperative to understand experiences and concerns to better inform support measures for the oncology workforce. Methods: Three anonymous online surveys were conducted during the COVID-19 pandemic (S1, Apr/May 2020;S2, Jul/Aug 2020;S3, Feb/Mar 2021). Longitudinal analysis of responses at these timepoints were conducted. Here, we present responses to questions on job demands and resources, and perceived job performance since COVID-19 (JP-CV). Results: We analysed 3894 individual responses (S1, n=1520;S2, n=942;S3, n=1432): 53% (n=1961/3731) female, 45% (n=1679/3731) =/ 100 countries. There has been significant increases from S1 to S3 (p

PURPOSE BEACON CRC evaluated encorafenib plus cetuximab with or without binimetinib versus investigators' choice of irinotecan or FOLFIRI plus cetuximab in patients with BRAFV600E–mutant metastatic colorectal cancer (mCRC), after progression on 1-2 prior regimens. In the previously reported primary analysis, encorafenib, binimetinib plus cetuximab (ENCO/BINI/CETUX; triplet) and encorafenib plus cetuximab (ENCO/CETUX; doublet) regimens improved overall survival (OS) and objective response rate (ORR; by blinded central review) versus standard of care. The purpose of this analysis was to report updated efficacy and safety data. METHODS In this open-label, phase III trial, 665 patients with BRAF V600E–mutant mCRC were randomly assigned 1:1:1 to receive triplet, doublet, or control. Primary end points were OS and independently reviewed ORR comparing triplet to control. OS for doublet versus control was a key secondary end point. Updated analyses include 6 months of additional follow-up and ORR for all randomized patients. RESULTS Patients received triplet (n = 224), doublet (n = 220), or control (n = 221). Median OS was 9.3 months (95% CI, 8.2 to 10.8) for triplet and 5.9 months (95% CI, 5.1 to 7.1) for control (hazard ratio [HR], 0.60 [95% CI, 0.47 to 0.75]). Median OS for doublet was 9.3 months (95% CI, 8.0 to 11.3) (HR v control, 0.61 [95% CI, 0.48 to 0.77]). Confirmed ORR was 26.8% (95% CI, 21.1% to 33.1%) for triplet, 19.5% (95% CI, 14.5% to 25.4%) for doublet, and 1.8% (95% CI, 0.5% to 4.6%) for control. Adverse events were consistent with the prior primary analysis, with grade ≥ 3 adverse events in 65.8%, 57.4%, and 64.2% for triplet, doublet, and control, respectively. CONCLUSION In the BEACON CRC study, encorafenib plus cetuximab improved OS, ORR, and progression-free survival in previously treated patients in the metastatic setting compared with standard chemotherapy. Based on the primary and updated analyses, encorafenib plus cetuximab is a new standard care regimen for previously treated patients with BRAF V600E mCRC.

The heterogenous nature of colorectal cancer (CRC) renders it a major clinical challenge. Increasing genomic understanding of CRC has improved our knowledge of this heterogeneity and the main cancer drivers, with significant improvements in clinical outcomes. Comprehensive molecular characterization has allowed clinicians a more precise range of treatment options based on biomarker selection. Furthermore, this deep molecular understanding likely extends therapeutic options to a larger number of patients. The biological associations of consensus molecular subtypes (CMS) with clinical outcomes in localized CRC have been validated in retrospective clinical trials. The prognostic role of CMS has also been confirmed in the metastatic setting, with CMS2 having the best prognosis, whereas CMS1 tumors are associated with a higher risk of progression and death after chemotherapy. Similarly, according to mesenchymal features and immunosuppressive molecules, CMS1 responds to immunotherapy, whereas CMS4 has a poorer prognosis, suggesting that a CMS1 signature could identify patients who may benefit from immune checkpoint inhibitors regardless of microsatellite instability (MSI) status. The main goal of these comprehensive analyses is to switch from "one marker-one drug" to "multi-marker drug combinations" allowing oncologists to give "the right drug to the right patient." Despite the revealing data from transcriptomic analyses, the high rate of intra-tumoral heterogeneity across the different CMS subgroups limits its incorporation as a predictive biomarker. In clinical practice, when feasible, comprehensive genomic tests should be performed to identify potentially targetable alterations, particularly in RAS/BRAF wild-type, MSI, and right-sided tumors. Furthermore, CMS has not only been associated with clinical outcomes and specific tumor and patient phenotypes but also with specific microbiome patterns. Future steps will include the integration of clinical features, genomics, transcriptomics, and microbiota to select the most accurate biomarkers to identify optimal treatments, improving individual clinical outcomes. In summary, CMS is context specific, identifies a level of heterogeneity beyond standard genomic biomarkers, and offers a means of maximizing personalized therapy.

Background Young oncologists are at particular risk of professional burnout, and this could have a significant impact on their health and care of their patients. The coronavirus disease 2019 (COVID-19) pandemic has forced rapid changes in professionals' jobs and training, with the consequent physical and psychological effects. We aimed to characterize burnout levels and determinants in young oncologists, and the effects of the pandemic on their training and health. Methods Two online surveys were conducted among oncology residents and young oncology specialists in Spain. The first addressed professional burnout and its determinants before the COVID-19 pandemic, while the second analyzed the impact of the pandemic on health care organization, training, and physical and psychological health in the same population. Results In total, 243 respondents completed the first survey, and 263 the second; 25.1% reported significant levels of professional burnout. Burnout was more common among medical oncology residents (28.2%), mainly in their second year of training. It was significantly associated with a poor work–life balance, inadequate vacation time, and the burnout score. Nearly three-quarters of respondents (72%) were reassigned to COVID-19 care and 84.3% of residents missed part of their training rotations. Overall, 17.2% of this population reported that they had contracted COVID-19, 37.3% had scores indicating anxiety, and 30.4% moderate to severe depression. Almost a quarter of young oncologists (23.3%) had doubts about their medical vocation. Conclusions Burnout affects a considerable number of young oncologists. The COVID-19 pandemic has had a profound impact on causes of burnout, making it even more necessary to periodically monitor it to define appropriate detection and prevention strategies., Highlights • Oncologists are susceptible to burnout. The COVID-19 pandemic has significantly impacted health care workers' mental health. • This study analyzes professional burnout and its determinants as well as the impact of COVID-19 among young oncologists. • Ensuring specialized training and preventing burnout are essential to ensure quality medical oncology care in the future.

Summary Background HER2 amplification has been identified in 2–3% of patients with colorectal cancer, although there are currently no approved HER2-targeted therapies for colorectal cancer. We aimed to study the antitumour activity and safety of trastuzumab deruxtecan (an antibody–drug conjugate of humanised anti-HER2 antibody with topoisomerase I inhibitor payloads) in patients with HER2-expressing metastatic colorectal cancer. Methods DESTINY-CRC01 is an open-label, phase 2 study that recruited patients from 25 clinics and hospitals in Italy, Japan, Spain, the UK, and the USA. Eligible patients had centrally confirmed HER2-expressing metastatic colorectal cancer that had progressed on two or more previous regimens (HER2-targeted therapies other than trastuzumab deruxtecan permitted), were aged 18 years or older (≥20 years in Japan), had an Eastern Cooperative Oncology Group score of 0 or 1, and had RAS and BRAFV600E wild-type tumours. Patients were enrolled into one of three cohorts by HER2 expression level: cohort A (HER2-positive, immunohistochemistry [IHC] 3+ or IHC2+ and in-situ hybridisation [ISH]-positive), cohort B (IHC2+ and ISH-negative), or cohort C (IHC1+). Patients received 6·4 mg/kg trastuzumab deruxtecan intravenously every 3 weeks until disease progression, unacceptable adverse events, withdrawal of consent, or death. The primary endpoint was confirmed objective response rate in cohort A by independent central review which was assessed in the full analysis set and safety was assessed in the safety analysis set. Both the full analysis set and the safety analysis set included all patients who received one or more doses of trastuzumab deruxtecan. This ongoing trial is registered with ClinicalTrials.gov , number NCT03384940 . Findings Between Feb 23, 2018, and July 3, 2019, 78 patients were enrolled in the study (53 in cohort A, seven in cohort B, and 18 in cohort C), all of whom received at least one dose of study drug. For the 53 (68%) patients with HER2-positive tumours (cohort A), a confirmed objective response was reported in 24 (45·3%, 95% CI 31·6–59·6) patients after a median follow-up of 27·1 weeks (IQR 19·3–40·1). Grade 3 or worse treatment-emergent adverse events that occurred in at least 10% of all participants were decreased neutrophil count (17 [22%] of 78) and anaemia (11 [14%]). Five patients (6%) had adjudicated interstitial lung disease or pneumonitis (two grade 2; one grade 3; two grade 5, the only treatment-related deaths). Interpretation Trastuzumab deruxtecan showed promising and durable activity in HER2-positive metastatic colorectal cancer refractory to standard treatment, with a safety profile consistent with that reported in previous trastuzumab deruxtecan trials. Interstitial lung disease and pneumonitis are important risks requiring careful monitoring and prompt intervention. Funding Daiichi Sankyo.

Protocol tittle: Study of BO-112 with pembrolizumab for colorectal or gastric/GEJ cancer with liver metastasis.Background: Gastric (GC), oesophagogastric junction (EGJC) and colorectal tumors (CRC) with microsatellite stability (MSS) are poorly responders to PD(L)-1 inhibition, due to low CD8+ T cell infiltration and PD-L1 expression. Therefore, modulation of the tumor microenvironment (TME) could increase disease control. In these tumors the presence of liver lesions is difficult to control because of the hepatic immune tolerance. Control of the hepatic disease could increase survival.BO-112 is a non-coding dsRNA agonist of TLR3, MDA5 and RIG-I which activates the innate and adaptative immune response, inducing apoptosis and immunogenic cell death, with a local and a systemic effect. A prior Phase I trial showed that the combination of pembrolizumab and intratumoral (IT) BO-112 has a good safety profile and encouraging activity. Study design: This is a single arm phase IIa trial to assess the efficacy of intrahepatic IT BO-112 and iv pembrolizumab in 3W cycles in patients with MSS CRC, GC or EGJ tumors. Up to 69 patients with at least one liver lesion and 2 prior lines for CRC and 1 for GC/EGJC will be enrolled. Primary endpoints: ORR and related TEAEs ≥ grade 3. Secondary endpoints: ORR (iRECIST), PFS, 6-months OS and safety. Exploratory endpoint: Changes in TME (PD-L1 expression and CD8+ T cell infiltration) from baseline to C2D1.Results: A total of 11 CRC and 7 GC/EGJC patients were enrolled since July 2020. This abstract focuses on the CRC patients´ biomarker expression. These patients had low PD-L1 CPS (combined positive score) expression and CD8+ T cell infiltration with a median value of 5 and 4%, respectively, in the TME at baseline. Following two IT BO-112 injections, an important increase in PD-L1 expression and CD8+ T cell infiltration was observed in 5 and 7 patients, respectively. PD-L1 CPS median value increased to 37.9 while CD8+ T cell infiltration median values raised to 12.9%.Conclusions: A meaningful increase in PD-L1 expression and CD8+ T cell infiltration was achieved in MSS CRC patients after one cycle of BO-112-pembrolizumab. Table 1.Baseline characteristics and TME changesBaseline characteristicsCRC N=11Demographics-Sex-Male-Female-Age (mean, range)7 (63.6%)4 (36.4%)55 (38-74)Location of primary tumor-Right colon-Left colon2 (36.4%)7 (63.6%)Presence of extrahepatic disease-No-YesLocation of the extrahepatic disease-Lungs-Lymph nodes-Ohers (bone, adrenal gland, peritoneum, pancreas)2 (18.2%)9 (81.8%)6 (54.5%)5 (45.5%)1 (9.1%)Molecular characteristics:-MMR status-MSS-KRAS-Wild type-Mutant -PD-L1-CPS Citation Format: Mariano Ponz-Sarvisé, Elena Élez, Andrés Muñoz, Marc Van den Eynde, Antonio Gaetano Rampoldi, Alain Hendlisz, Hans Prenen, Mercedes Rodríguez, María Teresa Cano, Marya Chaney, Helena Escuin, Vanesa Pons, Marisol Quintero, Andrés Cervantes. Phase IIa open-label clinical study of intratumoural administration of BO-112 in combination with pembrolizumab in subjects with liver metastasis from colorectal cancer or gastric/gastro-oesophageal junction cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT192.

Background Women represent an increasing proportion of the oncology workforce; however, globally this does not translate into leadership roles, reflecting disparities in career opportunities between men and women. The Spanish Society of Medical Oncology (SEOM) undertook a survey to investigate gender disparity in the Spanish oncology context. Design An online survey was made available to SEOM medical oncologists between February and May 2019. It included demographics, professional context and achievements, parenthood and family conciliation issues, workplace gender bias, and approaches to address disparities. Results Of the 316 eligible respondents, 71.5% were women, 59.5% were aged 45 or younger, and 66.1% had children. Among women, 12.4% were division or unit heads, compared with 45.5% of men, with most women (74.3%) being attending medical oncologists, compared with 45.5% of men. More males were professors (34.4% versus 14.2% of females), had a PhD (46.7% versus 28.8%), and/or had led clinical research groups (41.1% versus 9.7%). Spending time overseas after completing a residency was also more common for men than women (34.4% versus 20.4%). Professional satisfaction was similar between genders, driven primarily by patient care and intellectual stimulation. More women (40.7%) considered parenthood to have a strong negative impact on their career, compared with men (9.0%). Main perceived barriers to gender equality included a lack of work–life balance (72.6% women, 44.4% men), bias of peers and superiors (50.0% women, 18.9% men), and different career goals (41.2% women, 24.4% men). Preferred solutions included educational programs and scholarships (52.9%), communication and leadership training (35.8%), childcare at conferences (33.2%), and postmaternity return-to-work incentives (32.0%). Conclusion There is a clear paucity of equal opportunities for female oncologists in Spain. This can be addressed by encouraging professional development and merit recognition particularly for younger female oncologists, and empowering women to be involved in management and leadership of institutions and professional societies., Highlights • Under-representation of women in leadership roles in oncology is a widely acknowledged issue receiving global attention. • This study is a national description of leadership and educational opportunities in terms of gender and family circumstances. • Perceptions of gender bias in the workplace gender inequality or family conciliation issues and are described. • Initiatives for equal opportunities in oncology are needed supporting female academic career development and recognition.

Purpose: This open-label, dose-finding phase Ib/II study reports the safety and activity of the first combination use with BRAF inhibitor (BRAFi) encorafenib plus MEK inhibitor (MEKi) binimetinib in patients with BRAF V600E–mutant solid tumors. Patients and Methods: In phase I, the recommended phase 2 doses (RP2D) were established (primary objective). In phase II, the clinical activity of the combination at the RP2D was assessed (primary objective) in patients with BRAF-mutant metastatic colorectal cancer (mCRC), BRAFi-treated BRAF-mutant melanoma, and BRAFi-naïve BRAF-mutant melanoma. Results: A total of 126 patients with BRAF-mutant solid tumors were enrolled (phase I: 47 patients; phase II: 79 patients). The RP2D was encorafenib 450 mg once daily plus binimetinib 45 mg twice daily and pharmacokinetic data suggest that drug exposures of each agent were similar in combination compared with single-agent studies. In the phase II cohorts, confirmed responses were seen in two of 11 (18%) evaluable patients with mCRC, 11 of 26 (42%) evaluable patients with BRAFi-pretreated melanoma, and 28 of 42 (67%) BRAFi-naïve patients with melanoma. The most common grade 3/4 adverse event in phase II was increased alanine aminotransferase. Conclusions: The combination of encorafenib (450 mg) plus binimetinib (45 mg) showed acceptable tolerability and encouraging activity in patients with BRAF V600–mutant tumors, which led to the dose selection for the melanoma COLUMBUS study. The safety profile of the combination was consistent with other approved BRAFi plus MEKi regimens, with several differences, including lower rates of dose-limiting pyrexia, arthralgia, and photosensitivity.

Fusobacterium nucleatum; Càncer de recte avançat local; Quimioteràpia preoperatòria Fusobacterium nucleatum; Cáncer de recto avanzado local; Quimiorradioterapia preoperatoria Fusobacterium nucleatum; Locally advanced rectal cancer; Preoperative chemoradiotherapy Background Accumulating evidence has identified Fusobacterium as an important pathogenic gut bacterium associated with colorectal cancer. Nevertheless, only limited data exist about the role of this bacterium in locally advanced rectal cancer (LARC). In this study, we quantified Fusobacterium nucleatum in untreated and post-neoadjuvant chemoradiotherapy (nCRT) samples from LARC patients and investigated its association with therapy response and survival. Patients and methods A total of 254 samples from 143 patients with rectal adenocarcinomas were analyzed for the presence and abundance of F. nucleatum using RNA in situ hybridization and digital image analysis. Assay accuracy was determined using infected cell lines and tumor samples with available quantitative PCR data. We studied the impact of F. nucleatum load on pathologic complete response and relapse-free survival. Treatment-induced changes were evaluated in paired pre- and post-nCRT samples (n = 71). Finally, tumor microenvironment changes during nCRT were assessed in paired samples (n = 45) by immune contexture analysis. Results F. nucleatum tissue levels by RNA in situ hybridization strongly correlated with quantitative PCR (r = 0.804, P < 0.001). F. nucleatum abundance was higher in untreated [median, 7.4; 95% confidence interval (3.7–16.2)] compared with treated [median, 1.6; 95% confidence interval (1.3–2.4)] tumors (P

Biomarcadors; Càncer colorectal; Classificació molecular Biomarcadores; Cáncer colorrectal; Clasificación molecular Biomarkers; Colorectal cancer; Molecular classification Colorectal cancer (CRC) is a heterogeneous disease representing a therapeutic challenge, which is further complicated by the common occurrence of several molecular alterations that confer resistance to standard chemotherapy and targeted agents. Mechanisms of resistance have been identified at multiple levels in the epidermal growth factor receptor (EGFR) pathway, including mutations in KRAS, NRAS, and BRAFV600E, and in the HER2 and MET receptors. These alterations represent oncogenic drivers that may co-exist in the same tumor with other primary and acquired alterations via a clonal selection process. Other molecular alterations include DNA damage repair mechanisms and rare kinase fusions, potentially offering a rationale for new therapeutic strategies. In recent years, genomic analysis has been expanded by a more complex study of epigenomic, transcriptomic, and microenvironment features. The Consensus Molecular Subtype (CMS) classification describes four CRC subtypes with distinct biological characteristics that show prognostic and potential predictive value in the clinical setting. Here, we review the panorama of actionable targets in CRC, and the developments in more recent molecular tests, such as liquid biopsy analysis, which are increasingly offering clinicians a means of ensuring optimal tailored treatments for patients with metastatic CRC according to their evolving molecular profile and treatment history

Oncologia de precisió; Assaigs clínics; Preselecció molecular Oncología de precisión; Ensayos clínicos; Preselección molecular Precision oncology; Clinical Trials; Molecular prescreening Most academic precision oncology programs have been designed to facilitate enrollment of patients in early clinical trials with matched targeted agents. Over the last decade, major changes were seen both in the targetable molecular alteration landscape and in drug development trends. In this article, we describe how the Vall d’Hebron Institute of Oncology molecular prescreening program adapted to a dynamic model of biomarker-drug codevelopment. We started with a tumor-agnostic hotspot mutation panel plus in situ hybridization and immunohistochemistry of selected markers and subsequently transitioned to tumor-specific amplicon-based next-generation sequencing (NGS) tests together with custom copy number, fusion, and outlier gene expression panels. All assays are optimized for archived formalin-fixed paraffin-embedded tumor tissues without matched germline sequencing. In parallel, biomarker-matched trials evolved from a scenario of few targets and large populations (such as PI3K inhibitors in PIK3CA mutants) to a complex situation with many targets and small populations (such as multiple targetable fusion events). Recruitment rates in clinical trials with mandatory biomarkers decreased over the last 3 years. Molecular tumor board meetings proved critical to guide oncologists on emerging biomarkers for clinical testing and interpretation of NGS results. The substantial increase of immunotherapy trials had a major impact in target prioritization and guided clinical implementation of new markers, such as tumor mutational burden, with larger exon-based NGS assays and gene expression signatures to capture microenvironment infiltration patterns. This new multiomics era of precision oncology is expected to increase the opportunities for early clinical trial matching.

Biomarcadors; Neoplàsies colorectals; Mutacions Biomarcadores; Neoplasias colorrectales; Mutaciones Biomarkers; Colorectal neoplasms; Mutations Colorectal cancer (CRC) is a public health problem: it is the third most common cancer in men (746,000 new cases/year) and the second in women (614,000 new cases/year), representing the second leading cause of death by cancer worldwide. The survival of patients with metastatic CRC (mCRC) has increased prominently in recent years, reaching a median of 25 to 30 months. A growing number of patients with mCRC are candidates to receive a treatment in third line or beyond, although the optimal drug regimen and sequence are still unknown. In this situation of refractoriness, there are several alternatives: (1) To administer sequentially the 2 oral drugs approved in this indication: trifluridine/tipiracil and regorafenib, which have shown a statistically significant benefit in progression-free survival and overall survival with a different toxicity profile. (2) To administer cetuximab or panitumumab in treatment-naive patients with RAS wild type, which is increasingly rare because these drugs are usually indicated in first- or second-line. (3) To reuse drugs already administered that were discontinued owing to toxicity or progression (oxaliplatin, irinotecan, fluoropyrimidine, antiangiogenics, anti-epidermal growth factor receptor [if RAS wild-type]). High-quality evidence is limited, but this strategy is often used in routine clinical practice in the absence of alternative therapies especially in patients with good performance status. (4) To use specific treatments for very selected populations, such as trastuzumab/lapatinib in mCRC human epidermal growth factor receptor 2-positive, immunotherapy in microsatellite instability, intrahepatic therapies in limited disease or primarily located in the liver, although the main recommendation is to include patients in clinical trials.

International audience; Background: Despite a protracted disease course and multiple available therapies, patients with well-differentiated neuroendocrine tumors (NETs) inevitably experience disease progression. Programmed death–ligand 1 (PD-L1) has been associated with NET progression and prognosis. The multicohort, phase 1 KEYNOTE-028 study (ClinicalTrials.gov identifier NCT02054806) evaluated the activity and safety of the anti–programmed cell death protein 1 immunotherapy pembrolizumab in patients with well-differentiated or moderately-differentiated NETs. Methods: Patients with PD-L1–positive, locally advanced or metastatic carcinoid or well–differentiated or moderately-differentiated pancreatic NETs (pNETs) were enrolled into separate cohorts and received pembrolizumab at a dose of 10 mg/kg every 2 weeks for up to 2 years. The objective response rate was the primary endpoint (as per Response Evaluation Criteria in Solid Tumors version 1.1, by investigator review). Safety was a secondary endpoint. Results: Of 170 and 106 patients, respectively, who had evaluable samples among those screened for the carcinoid and pNET cohorts, 21% and 25%, respectively, had PD-L1–positive tumors; of these, 25 and 16 patients, respectively, were eligible and treated. The median follow-up was 20 months (range, 2-35 months) and 21 months (range, 5-32 months), respectively. The objective response rate was 12.0% (95% CI, 2.5%-31.2%) and 6.3% (95% CI, 0.2%-30.2%), respectively; 3 partial responses occurred among the carcinoid cohort and 1 among the pNET cohort. The median duration of response in the carcinoid cohort was 9.2 months (range, 6.9-11.1 months), and was not reached in the pNET cohort. No complete responses occurred. Treatment-related adverse events occurred in 68% and 69% of patients, respectively, most often diarrhea (7 patients in the carcinoid cohort and 4 patients in the pNET cohort) and fatigue (6 patients in each cohort). Hypothyroidism was the most common immune-mediated adverse event (5 patients in the carcinoid cohort and 2 patients in the pNET cohort). Conclusions: Pembrolizumab demonstrated antitumor activity in a subset of patients with NETs and was well-tolerated.

Introduction: Molecular profiling has led to significantly longer survival in metastatic colorectal cancer (mCRC) patients. Clinical guidelines recommend testing for KRAS/NRAS, BRAF and MSI status, and new biomarkers such as HER2 amplification and NTRK fusions have emerged more recently in refractory CRC, supported by overwhelming clinical relevance. These biomarkers can guide treatment management to improve clinical outcomes in these patients. Areas covered: Preclinical and clinical data over the last decade were reviewed for known and novel biomarkers with clinical implications in refractory CRC. Molecular alterations are described for classic and novel biomarkers, and data for completed and ongoing studies with targeted and immunotherapies are presented. Expert opinion: Use of targeted therapies based on biomarker testing in CRC has enabled impressive improvements in clinical outcomes in refractory patients. BRAF, MSI, NRAS and KRAS should be tested upfront in all patients given their indisputable therapeutic implications. Other molecular alterations such as HER2 and NTRK are emerging. Testing for these alterations may further improve outcomes for refractory CRC patients. Nonetheless, many key aspects remain to be defined including the optimal timing and technique for testing, the most adequate panel, and whether all patients should be tested for all alterations.

Background Plocabulin (PM060184) is a novel marine-derived microtubule inhibitor that acts as an antitumor agent. This first-in-human study evaluated dose-limiting toxicities (DLT) to define the maximum tolerated dose (MTD) and phase II recommended dose (RD) of plocabulin given as a 10-min infusion on Day (D) 1, D8 and D15 every four weeks. Patients and methods Forty-four patients with advanced solid tumors received plocabulin following an accelerated titration design. Results Plocabulin was escalated from 1.3 mg/m2 to 14.5 mg/m2, which was defined as the MTD. No RD was confirmed, because frequent dose delays and omissions resulted in low relative dose intensity (66%) at the 12.0 mg/m2 expansion cohort. The main DLT was grade 3 peripheral sensory neuropathy (PSN); other DLTs were grade 4 tumor lysis syndrome, grade 4 cardiac failure and grade 3 myalgia. Toxicities were mainly mild to moderate, and included abdominal pain, myalgia, fatigue, nausea, and vomiting. Myelosuppression was transient and manageable. Plocabulin had a half-life of ~4 h and a wide diffusion to peripheral tissues. Antitumor response was observed in cervix carcinoma and heavily pretreated metastatic non-small cell lung cancer patients, and disease stabilization (≥3 months) in patients with colorectal, thymic, gastrointestinal stromal and breast tumors, among others. The clinical benefit rate was 33%. Conclusion The main DLT of plocabulin was PSN, as anticipated for a tubulin-binding agent. Since encouraging antitumor activity was observed, efforts to improve toxicity and to find the RD were planned in other trials evaluating D1&D8 and D1-D3 plus D15-D17 schedules.

Author(s): Cohen, Roger B; Delord, Jean-Pierre; Doi, Toshihiko; Piha-Paul, Sarina A; Liu, Stephen V; Gilbert, Jill; Algazi, Alain P; Damian, Silvia; Hong, Ruey-Long; Le Tourneau, Christophe; Day, Daphne; Varga, Andrea; Elez, Elena; Wallmark, John; Saraf, Sanatan; Thanigaimani, Pradeep; Cheng, Jonathan; Keam, Bhumsuk | Abstract: ObjectivesTreatment options for patients with unresectable or metastatic salivary gland carcinoma (SGC) are limited. Safety and efficacy of pembrolizumab for SGC expressing programmed death ligand 1 (PD-L1) were explored.Materials and methodsA cohort of patients with advanced, PD-L1-positive SGC was enrolled in the nonrandomized, multicohort, phase Ib trial of pembrolizumab in patients with PD-L1-positive advanced solid tumors (KEYNOTE-028; NCT02054806). Key inclusion criteria included recurrent or metastatic disease, failure of prior systemic therapy, and PD-L1 expression on ≥1% of tumor or stroma cells (per a prototype immunohistochemistry assay). Patients received pembrolizumab 10 mg/kg every 2 weeks for ≥2 years or until confirmed disease progression or unacceptable toxicity. Primary end point was objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 by investigator review.ResultsTwenty-six patients with PD-L1-positive SGC were enrolled and treated; median age was 57 years, 88% were men, and 74% had received prior therapy for recurrent/metastatic disease. Confirmed objective response rate after median follow-up of 20 months was 12% (95% confidence interval, 2%-30%), with 3 patients achieving partial response; there were no complete responses. Median duration of response was 4 months (range, 4 to 21 mo). Treatment-related adverse events occurred in 22 patients (85%), resulting in discontinuation in 2 patients and death in 1 (interstitial lung disease); those occurring in ≥15% of patients were diarrhea, decreased appetite, pruritus, and fatigue.ConclusionsPembrolizumab demonstrated promising antitumor activity and a manageable safety profile in patients with advanced, PD-L1-positive SGC.

Purpose The multicohort phase Ib KEYNOTE-028 (NCT02054806) study was designed to evaluate the safety and efficacy of pembrolizumab, an anti–programmed death 1 monoclonal antibody, in patients with programmed death ligand 1 (PD-L1) –positive advanced solid tumors. The results from the advanced endometrial cancer cohort are reported. Patients and Methods Female patients with locally advanced or metastatic PD-L1–positive endometrial cancer who had experienced progression after standard therapy were eligible. Patients received pembrolizumab 10 mg/kg every 2 weeks for up to 24 months or until progression or unacceptable toxicity. Primary efficacy end point was objective response rate by RECIST (version 1.1). Secondary end points included safety, duration of response (DOR), progression-free survival, and overall survival. The data cutoff was February 17, 2016. Results Of 75 patients screened, 36 (48.0%) had PD-L1–positive tumors, and 24 (32.0%) were enrolled. Fifteen (62.5%) of these 24 patients had received at least two previous lines of therapy for advanced disease. Three patients (13.0%) achieved confirmed partial response (95% CI, 2.8% to 33.6%); the median DOR was not reached. Two patients were still receiving treatment and exhibiting continued response at time of data cutoff. Three additional patients (13.0%) achieved stable disease, with a median duration of 24.6 weeks. One patient who achieved partial response had a polymerase E mutation. Thirteen patients (54.2%) experienced treatment-related adverse events (AEs), with fatigue (20.8%), pruritus (16.7%), pyrexia (12.5%), and decreased appetite (12.5%) occurring in ≥ 10% of patients. Grade 3 treatment-related AEs were reported in four patients. No patient experienced a grade 4 AE, and no patient discontinued treatment because of an AE. Conclusion Pembrolizumab demonstrated a favorable safety profile and durable antitumor activity in a subgroup of patients with heavily pretreated advanced PD-L1–positive endometrial cancer.

Preclinical evidence suggests that concomitant BRAF and EGFR inhibition leads to sustained suppression of MAPK signaling and suppressed tumor growth in BRAFV600E colorectal cancer models. Patients with refractory BRAFV600-mutant metastatic CRC (mCRC) were treated with a selective RAF kinase inhibitor (encorafenib) plus a monoclonal antibody targeting EGFR (cetuximab), with (n = 28) or without (n = 26) a PI3Kα inhibitor (alpelisib). The primary objective was to determine the maximum tolerated dose (MTD) or a recommended phase II dose. Dose-limiting toxicities were reported in 3 patients receiving dual treatment and 2 patients receiving triple treatment. The MTD was not reached for either group and the phase II doses were selected as 200 mg encorafenib (both groups) and 300 mg alpelisib. Combinations of cetuximab and encorafenib showed promising clinical activity and tolerability in patients with BRAF-mutant mCRC; confirmed overall response rates of 19% and 18% were observed and median progression-free survival was 3.7 and 4.2 months for the dual- and triple-therapy groups, respectively.Significance: Herein, we demonstrate that dual- (encorafenib plus cetuximab) and triple- (encorafenib plus cetuximab and alpelisib) combination treatments are tolerable and provide promising clinical activity in the difficult-to-treat patient population with BRAF-mutant mCRC. Cancer Discov; 7(6); 610–9. ©2017 AACR.See related commentary by Sundar et al., p. 558.This article is highlighted in the In This Issue feature, p. 539

[EN] BACKGROUND: Liquid biopsy offers a minimally invasive alternative to tissue-based evaluation of mutational status in cancer. The goal of the present study was to evaluate the aggregate performance of OncoBEAM RAS mutation analysis in plasma of colorectal cancer (CRC) patients at 10 hospital laboratories in Spain where this technology is routinely implemented. METHODS: Circulating cell-free DNA from plasma was examined for RAS mutations using the OncoBEAM platform at each hospital laboratory. Results were then compared to those obtained from DNA extracted from tumour tissue from the same patient. RESULTS: The overall percentage agreement between plasma-based and tissue-based RAS mutation testing of the 236 participants was 89% (210/236; kappa, 0.770 (95% CI: 0.689-0.852)). Re-analysis of tissue from all discordant cases by BEAMing revealed two false negative and five false positive tumour tissue RAS results, with a final concordance of 92%. Plasma false negative results were found more frequently in patients with exclusive lung metastatic disease. CONCLUSIONS: In this first prospective real-world RAS mutation performance comparison study, a high overall agreement was observed between results obtained from plasma and tissue samples. Overall, these findings indicate that the plasma-based BEAMing assay is a viable solution for rapid delivery of RAS mutation status to determine mCRC patient eligibility for anti-EGFR therapy., This work was supported by Sysmex Inostics, Inc as well as the AES Programme [Grant Numbers PI15/00934, PT17/0015/0006]. The funders had no involvement in the writing of this manuscript but did review for medical accuracy prior to submission.

2542 Background: Detection of ctDNA is a promising tool for managing pts in oncology. Most methods require whole-genome sequencing of tumor samples followed by the design of personalized panels for tracking purposes. In this work, we evaluated the prognostic and predictive value of total ctDNA quantification, using shallow whole-genome sequencing (shWGS) exclusively from plasma samples, in a prospective cohort of pts treated with ICIs in early clinical trials. Methods: IchorCNA pipeline was used to quantify ctDNA of shWGS from plasma ctDNA samples of pts treated with ICIs in phase 1 trials, collected at baseline and prior to cycle 2 (prec2). We investigated the association and correlation of ctDNA levels with surrogate markers for tumor burden (LDH levels, summatory of target lesions (TL), liver metastasis) using Spearman and Kruskal-Wallis tests. Kaplan-Meier estimates of overall survival (OS) of pts with baseline detectable ctDNA levels versus undetectable ctDNA were calculated. A multivariate Cox proportional hazards model, including continuous classical prognostic factors (LDH, albumin, hemoglobin, derived Neutrophil-to-Lymphocyte ratio (dNLR), platelets, number of metastases sites, ECOG PS) and ctDNA was performed. An estimate of progression free survival (PFS) of pts with ctDNA increase levels in preC2 versus a non-increase group was evaluated. Results: Since January 2018, 113 pts with no standard-treatment options were included. Median (m) follow up was 14.8 months (mo). Baseline ctDNA levels correlated significantly with baseline TL (R = 0.4, p < 0.001) and LDH levels (R = 0.61, p < 0.001). Pts with liver metastasis had higher levels of ctDNA (11,68 ng/ml) versus pts with no liver disease (2,31 ng/ml) (p < 0,001). In the survival analysis pts with detectable baseline ctDNA (74 pts) had significantly shorter OS compared with pts with undetectable ctDNA (39 pts); median 9.6 m (8.4 – 16.4) and NA m (13.6-NA), respectively (HR = 2.25 [1.18-4.29] p < 0.01). In the multivariate analysis, only ctDNA and albumin levels maintained the impact in OS (HR = 1.03, p < 0.05 and HR = 0.22, p < 0.05, respectively). Pts with early increases in ctDNA had a shorter PFS compared with those with a stabilization or decrease, median 1.9 m (1.6 – 4.0) and 3.0 m (2.6 – 3.8), respectively (HR = 2.19 [1.31-3.67], p < 0.01). Conclusions: Quantification of baseline ctDNA using shWGS is a strong independent prognostic factor. Early dynamic changes of ctDNA could be a useful tool to predict PFS outcomes.

10563 Background: Young-onset colorectal cancer (YOCR) is defined as diagnosis below the age of 50. Over the past decades, the incidence of YOCRC has increased at an alarming rate, but causes and pathogenesis still remain unknown. Early detection of colorectal cancer (CRC) has demonstrated to improve survival. Despite these facts, adults < 50 years old are not yet included in screening programs and YOCRC is not well characterized. We aimed to characterize the clinical and molecular characteristics of YOCRC in patients (pts) diagnosed at our institution. Methods: Consecutive pts with a diagnosis of CRC below the age of 50 visited for the first time at Vall d’Hebron University Hospital in Spain between January 2017 and October 2020 were included in the analysis. Data of clinicopathologic features and treatment were collected retrospectively from medical records. Results: 205 pts met the inclusion criteria, 111 (54%) were females, 8 (4%) presented a personal history of cancer at diagnosis and 109 (53%) a family history of cancer. Age at diagnosis was: < 30: 10 (5%), {30 – 40): 52 (25%), {40-45): 51 (25%), {45-50): 92 (45%). Site of primary tumor was: right colon: 50 (24%), left colon: 107 (52%): rectum: 48 (24%). Stage at diagnosis was I: 3 (1%), II: 14 (7%), III: 60 (29%), IV: 128 (63%). 6 of 14 (43%) and 44 of 60 patients (73%) with stage II and III CRC presented disease progression after initial treatment, respectively. Molecular status was: KRAS mutation: 74 (36%), NRAS mutation: 7 (3%), BRAF mutation: 12 (6%), MSI-H: 12 (6%). 43 pts (21%) had documentation of genetic counseling. Median (range) number of lines of treatment for metastatic disease was 3 (1-7), 53 pts (30%) received at least 4 lines of treatment. Median (range) number of metastatic sites was: 2 (1-6). 114 patients (55.6%) had died at the cut-off timepoint. Conclusions: YOCR is usually diagnosed with a more advanced stage than standard-onset CRC, with a poorer course of the disease. Further studies in young adults with CRC should address this phenomenon to understand the underlying causes, and prioritize genetic counseling. Our results support the unmet need of initiating screening programs in adults younger than 50 years, the urgency for a global consensus and a call for action.

3500 Background: In the phase III, randomized open-label KEYNOTE-177 (NCT02563002) study 1L pembrolizumab (pembro) versus chemotherapy (chemo) provided superior progression-free survival (PFS) at second interim analysis (IA2) in patients (pts) with MSI-H/dMMR mCRC. The study continued to final analysis of overall survival (OS), planned after 190 OS events or 12 months after IA2, whichever occurred first. We present results of the final analysis of OS, 12 months after IA2. Methods: A total of 307 pts with MSI-H/dMMR mCRC and ECOG PS 0 or 1 were randomized 1:1 to 1L pembro 200 mg Q3W for up to 2y or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab. Treatment continued until PD, unacceptable toxicity, pt/investigator decision to withdraw, or completion of 35 cycles (pembro only). Pts receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were OS and PFS (RECIST v1.1, central review). Secondary end points included ORR, duration of response (DOR) (RECIST v1.1, central review), and safety. For OS significance, the p-value had to meet a prespecified α of 0.0246 (one-sided). Sensitivity analyses to adjust for crossover effect were performed. Data cut-off for final analysis was Feb 19, 2021. Results: Median (range) study follow-up was 44.5 mo (36.0-60.3) with pembro vs 44.4 mo (36.2-58.6) with chemo. 56 (36%) pts crossed over from chemo to pembro, with 37 more receiving anti-PD-1/PD-L1 therapies off study (60% effective crossover rate in the ITT). The HR for OS favored pembro vs chemo with a trend toward reduction in the risk of death (HR 0.74; 95% CI, 0.53-1.03; P=0.0359; median not reached [NR] vs 36.7 mo); this difference did not reach statistical significance. Sensitivity analysis by the rank-preserving structure failure time model and inverse probability of censoring weighting showed OS HRs of 0.66 (95% CI 0.42-1.04) and 0.77 (95% CI 0.44-1.38), respectively. Pembro vs chemo met the prespecified criteria for PFS superiority at IA2. At final analysis, median PFS was 16.5 mo vs 8.2 mo (HR 0.59; 95% CI, 0.45-0.79), but was not formally tested per analysis plan. Confirmed ORR was 45.1% (20 CR, 49 PR) vs 33.1% (6 CR, 45 PR). Median (range) DOR was NR (2.3+ to 53.5+) vs 10.6 mo (2.8 to 48.3+), respectively. Treatment-related adverse events (TRAEs) occurred in 79.7% vs 98.6% of pts; 21.6% vs 66.4%, respectively, had grade ≥3 TRAEs. Conclusions: As 1L therapy for pts with MSI-H/dMMR mCRC, pembro vs chemo provides statistically superior PFS with fewer TRAEs, and is associated with a trend toward reduced mortality that did not meet statistical significance likely due to the high crossover rate from chemo to anti-PD1/PD-L1 therapies. Together these data confirm pembro as a new standard-of-care in the 1L for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02563002.

2597 Background: In order to improve the expected response rate (ORR) of less than 10% in cold tumors, several ICI combinations are being evaluated in clinical trials. However, most of these trials don’t require any biomarker and pts are included based solely in histology. We aimed to assess the benefit of ICI combinations in pts with unselected cold tumors included in early CT. Methods: ICI naïve pts with cold tumors treated from 2015 to 2021 with ICI combinations in early CT at VHIO were reviewed. Clinico-pathological data and anti-tumor activity were extracted from a prospective database. ORR was defined as per RECIST v1.1 and clinical benefit rate (CBR) as complete/partial response (CR/PR) + stable disease (SD) for ≥ 4 months (m). Kaplan Meier estimates of progression-free survival (PFS) and overall survival (OS) were calculated and a Cox model according to LIPI (Lung Immune Prognostic Index = baseline LDH and derived neutrophil to lymphocyte ratio) was constructed. Immune-related adverse events (irAE) were classified as per CTCAE v.4.03. Hyperprogressive disease (HPD) was evaluated using RECIST v1.1 (Matos et al, 2020). Results: Out of 97 pts, median age was 62y, 61% had ECOG 0 and 29.8% had LIPI 0 (good prognostic score). Most pts had microsatellite stable (MSS) colorectal cancer (60.8%) or ovarian cancer (14.4%). Regimens included anti-PD1/L1 + another ICI in 69% (most commonly anti-LAG3 [26,8%] and CD40 agonist [20.9%]), anti-PD1/L1 + other molecule in 21.7% (most commonly SHP2 inhibitor [33.3%] and anti p53-HDM2 [28.5%]) and bispecific antibodies in 9.3% (anti-PD1/L1 + anti-LAG3 or CD137 agonist). No patient achieved a response. CBR was 15.3% (11 pts with MSS colorectal cancer, 2 ovarian cancer, 1 olfactory neuroblastoma, 1 paraganglioma). 33 pts (34%) presented irAE, 15 pts (15.5%) had irAE ≥ G2, 4 pts (4.1%) had G3 irAE (dry mouth, hypertransaminasemia, myocarditis and neutrophils count decreased) and 1 patient (1%) had G4 hyperglicemia. 58 pts (59.7%) had progressive disease (PD) as best response, 19 of these pts (32.7%) presented irAE. Overall, 20 pts (20.6%) met definition of HPD, representing 34.4% of pts with PD as best response. Median PFS for overall and CBR population were 1.9 m (CI95% 1.7-2.0) and 5.9 m (5.4-NR), respectively. Median OS for overall population was 7.6 m (5.9-9.5), with a trend for improved OS if LIPI good score vs. others (12.6 m vs. 6.2 m, hazard ratio 1.9, (CI 95% 1.1-3.3), p = 0.02). Among hyperprogressors, median OS was 5.33 m (3.39 - NR) and significantly worse LIPI scores (intermediate [1] or poor [2]) were observed as compared to pts with CBR (75% vs 53.3% p = 0.001). Conclusions: ICI combinations demonstrated very limited activity in pts with unselected cold tumors. However, the risk for irAE and HPD remain substantial. Further drug-biomarker co-development strategies are urgently needed to increase the risk benefit ratio for these pts.

TPS149 Background: METamp is a secondary, or co-driving, genetic change in pts with mCRC and acquired resistance to anti-EGFR therapy, which can contribute to disease progression. In EGFR-resistant pts with mCRC and METamp, MET inhibition + an anti-EGFR agent could achieve disease control by targeting emerging MET pathway activation and maintaining EGFR pathway inhibition. Tepotinib is an oral, once-daily, highly selective, potent MET tyrosine kinase inhibitor (TKI). Tepotinib + the EGFR TKI gefitinib demonstrated improved outcomes in pts with EGFR-mutant METamp non-small cell lung cancer and acquired EGFR TKI resistance vs chemotherapy (INSIGHT: NCT01982955). In these pts, progression-free survival (PFS) was 16.6 vs 4.2 months (HR = 0.13; 90% CI: 0.04, 0.43) and overall survival (OS) was 37.3 vs 13.1 months (HR = 0.08; 90% CI: 0.01, 0.51). In pts with mCRC and acquired resistance to anti-EGFR antibody therapy due to METamp, tepotinib + anti-EGFR antibody cetuximab may be active and therefore provide an effective therapeutic option. Methods: This Phase II, multicenter, single-arm, open-label study will assess preliminary antitumor activity, safety and tolerability, and explore pharmacokinetic (PK) profiles of tepotinib + cetuximab in pts with RAS/BRAF wild-type left-sided mCRC and acquired resistance to anti-EGFR antibody-targeted therapy due to METamp. A safety run-in (6-12 pts) will evaluate the recommended Phase II dose of tepotinib to be used in combination with cetuximab (endpoint:dose-limiting toxicities). Enrollment is based on a confirmed advanced left-sided CRC diagnosis, with RAS/BRAF wild-type, documented previous anti-EGFR therapy and acquired resistance on the most recent anti-EGFR antibody and METamp confirmed by liquid and/or tissue biopsy. Pts must be ≥18 years old and have an Eastern Cooperative Oncology Group performance status of 0/1 and normal organ function. The study will screen sufficient pts to account for setting-specific METamp heterogenicity. Approximately 42 pts are planned to receive study treatment: ~22 in Cohort A (tepotinib second-line, outside US) and 20 in Cohort B (tepotinib ≥third-line, US only). Primary endpoint:investigator-assessed objective response (RECIST 1.1). Secondary endpoints are investigator-assessed duration of response (DoR) and PFS (RECIST 1.1), OS, tolerability and safety (NCI-CTCAE v5.0) and cetuximab immunogenicity (measured by antidrug antibody assays at the start and end of treatment). Additional endpoints include assessment of tepotinib and cetuximab PK profiles and expression of biomarkers of resistance (from blood and/or tissue samples). Retrospective assessment of best overall response, DoR and PFS by an independent review committee may be conducted. No formal statistical hypothesis will be tested in this exploratory study. Clinical trial information: NCT04515394.

6 Background: KEYNOTE-177 (NCT02563002) evaluated the antitumor activity of pembrolizumab (pembro) vs chemotherapy ± bevacizumab or cetuximab (chemo) as first-line therapy for patients with microsatellite-instability high/mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC). We present results of the final PFS analysis and analysis of PFS2. Methods: Patients with locally-determined MSI-H/dMMR mCRC and ECOG PS 0 or 1 were randomized 1:1 to first-line pembro 200 mg Q3W for up to 2 years or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab (chosen before randomization). Treatment continued until progression, unacceptable toxicity, patient/investigator decision to withdraw, or completion of 35 cycles (pembro only). Patients receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were PFS (RECIST v1.1, central review) and OS. Secondary end points included ORR (RECIST v1.1, central review) and safety. Exploratory endpoints included duration of response (DOR), PFS2 (time from randomization to progression on next line of therapy or any cause death), and health-related quality of life (HRQoL). Data cutoff was Feb 19, 2020. Results: At data cutoff a total of 307 patients were randomized (153 to pembro, 154 to chemo). Median (range) study follow-up was 32.4 mo (24.0-48.3). Pembro was superior to chemo for PFS (median 16.5 mo vs 8.2 mo; HR 0.60; 95% CI, 0.45-0.80; P= 0.0002). The 12- and 24-mo PFS rates were 55.3% and 48.3% with pembro vs 37.3% and 18.6% with chemo. Confirmed ORR was 43.8% vs 33.1%; median (range) DOR was not reached (2.3+ to 41.4+) with pembro vs 10.6 mo (2.8 to 37.5+) with chemo. PFS2 was longer with pembro vs chemo (median not reached vs 23.5 mo [HR 0.63; 95% CI, 0.45-0.88]). OS analysis is ongoing. Grade ≥3 treatment related adverse event (TRAE) rates were 22% vs 66% for pembro vs chemo. There were no grade 5 TRAEs in the pembro arm and 1 grade 5 intestinal perforation in the chemo arm. HRQoL scores were improved with pembro vs chemo. Conclusions: Pembro provided a statistically significant improvement in PFS vs chemo as first-line therapy for patients with MSI-H/dMMR mCRC, with fewer TRAEs observed. Furthermore, pembro provided a clinically meaningful improvement in PFS2 for patients with MSI-H/dMMR mCRC. Clinical trial information: NCT02563002.

Background: Moving stage III Colon Cancer (CC) into the precision medicine space is a priority in view of the lack of molecular markers driving adjuvant treatment. Retrospective studies have demonstrated the tremendous prognostic impact of circulating tumor DNA (ctDNA) analysis after curative intent surgery, and suggested that lack of conversion of ctDNA from detectable to undetectable after adjuvant chemotherapy reflects treatment failure. With these premises, we have designed the PEGASUS trial (EudraCT 2019-002074-32) to prove the feasibility of using liquid biopsy to guide the post-surgical and post-adjuvant clinical management of early colon cancer patients. Methods: PEGASUS is a prospective multicentric vanguard study designed to test the feasibility of performing serial interventional liquid biopsies (LB) for ctDNA determination in 140 microsatellite stable Stage-III and T4N0 Stage-II CC patients. The LUNAR1 (Guardant Health, Redwood City, CA, USA) will be used for ctDNA determination. For the efficacy analysis, the PEGASUS cohort will be compared with a cohort of 420 patients from the TOSCA trial (NCT00646607) population matched 3:1 for all known prognostic phenotypes. A post-surgical LB executed 2-4 weeks after surgery will guide a “Molecular Adjuvant” treatment as follows: i) ctDNA+ patients will receive CAPOX for 3 months and ii) ctDNA- patients will receive capecitabine (CAPE) for 6 months but will be retested after 1 cycle, and if found ctDNA+ will be switched to CAPOX treatment. Immediately after the end of “Molecular Adjuvant” treatment a further LB will be performed and instruct subsequent treatment. Positive patients (ctDNA+/+ and ctDNA-/+) will receive an up-scaled “Molecular Metastatic” systemic treatment for 6 months or until radiological progression or toxicity as follows: i) ctDNA+/+ patients will be treated with FOLFIRI; ii) ctDNA-/+ patients with CAPOX. These patients will be subjected to a LB after 3 months and at the end of treatment and in case of positivity will be switched to FOLFIRI. Patients experiencing ctDNA conversion to negative (ctDNA+/-) will receive a de-escalated treatment with CAPE for 3 months. 3 LB will be performed within 3 months and in case of positivity the patient will be switched to FOLFIRI. Patients with ctDNA-/- will be subjected to an interventional follow-up comprising 2 further LB and in case of positivity they will be switched to CAPOX treatment. PEGASUS is piggybacked to AlfaOmega (NCT04120935), a Master Observational Protocol that will follow patients from diagnosis to 5 years or recurrence/death (whichever comes first), collecting clinical data, radio images and biological samples. AlfaOmega provides a clinical and logistic ecosystem for the seamless integration of PEGASUS clinical results with the biological underpinning of colon cancer. Citation Format: Elena Elez, Filippo Pietrantonio, Andrea Sartore-Bianchi, Clara Montagut, Andres Cervantes, Stefania Sciallero, Maria Giulia Zampino, Stefania Mosconi, Valter Torri, Noelia Tarazona, Luca Lazzari, Paolo Luraghi, Susana Muñoz, Matteo Fassan, Enzo Medico, Livio Trusolino, Maria Rescigno, Salvatore Siena, Alberto Sobrero, Roberto Labianca, Josep Tabernero, Alberto Bardelli, Sara Lonardi, Silvia Marsoni. Post-surgical liquid biopsy-guided treatment of stage III and high-risk stage II colon cancer patients: The PEGASUS trial [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT263.

LBA4 Background: KEYNOTE-177 (NCT02563002) is a phase 3, randomized open-label study evaluating the efficacy and safety of pembrolizumab (pembro) versus standard of care chemotherapy ± bevacizumab or cetuximab (chemo) as first-line therapy for patients (pts) with microsatellite-instability high/mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC). We present results of the final PFS analysis. Methods: A total of 307 pts with MSI-H/dMMR mCRC as determined locally and ECOG PS 0 or 1 were randomly assigned 1:1 to first-line pembro 200 mg Q3W for up to 2 years or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab (chemo chosen prior to randomization). Treatment continued until PD, unacceptable toxicity, pt/investigator decision to withdraw, or completion of 35 cycles (pembro only). Patients receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were PFS (RECIST v1.1, central review) and OS. Key secondary end points included ORR (RECIST v1.1, central review), and safety. The data cutoff date for this interim analysis was Feb 19, 2020. The study will continue without changes to evaluate OS. Results: At data cutoff, 153 pts were randomized to pembro and 154 to chemo. Median (range) study follow-up was 28.4 mo (0.2-48.3) with pembro vs 27.2 mo (0.8-46.6) with chemo. Pembro was superior to chemo for PFS (median 16.5 mo vs 8.2 mo; HR 0.60; 95% CI, 0.45-0.80; P=0.0002). The 12- and 24-mo PFS rates were 55.3% and 48.3% with pembro vs 37.3% and 18.6% with chemo. Confirmed ORR was 43.8% vs 33.1%; median (range) duration of response was not reached (2.3+ to 41.4+) with pembro vs 10.6 mo (2.8 to 37.5+) with chemo. Grade 3-5 treatment related adverse event (AE) rates were 22% vs 66% for pembro vs chemo. One pt in the chemo arm died due to a treatment-related AE. Conclusions: Pembro provided a clinically meaningful and statistically significant improvement in PFS versus chemo as first-line therapy for pts with MSI-H/dMMR mCRC, with fewer treatment-related AEs observed and should be the new standard of care for these pts. Clinical trial information: NCT02563002 .