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Supplemental Figure 1. RPPA heat map of H460 cells treated with varying doses of radiation and ganetespib. Supplemental Figure 2. RPPA heat map of A549 cells treated with varying doses of radiation and ganetespib. Supplemental Figure 3. Western blot validation of some of the altered proteins seen on RPPA analysis in H460 cells. Supplemental Figure 4. The apoptosis indicated by Caspase cleavage in RPPA and western blot were confirmed by flow cytometry Annexin V analysis. Supplemental Figure 5. H460 xenograft recapitulated in vitro DNA damage and apoptosis results.

Purpose: Evidence suggests that PD-L1 can be induced with radiotherapy and may be an immune escape mechanism in cancer. Monitoring this response is limited, as repetitive biopsies during therapy are impractical, dangerous, and miss tumor stromal cells. Monitoring PD-L1 expression in both circulating tumor cells (CTCs) and circulating stromal cells (CStCs) in blood-based biopsies might be a practical alternative for sequential, noninvasive assessment of changes in tumor and stromal cells.Experimental Design: Peripheral blood was collected before and after radiotherapy from 41 patients with lung cancer, as were primary biopsies. We evaluated the expression of PD-L1 and formation of RAD50 foci in CTCs and a CStC subtype, cancer-associated macrophage-like cells (CAMLs), in response to DNA damage caused by radiotherapy at the tumor site.Results: Only 24% of primary biopsies had sufficient tissue for PD-L1 testing, tested with IHC clones 22c3 and 28-8. A CTC or CAML was detectable in 93% and 100% of samples, prior to and after radiotherapy, respectively. RAD50 foci significantly increased in CTCs (>7×, P < 0.001) and CAMLs (>10×, P = 0.001) after radiotherapy, confirming their origin from the radiated site. PD-L1 expression increased overall, 1.6× in CTCs (P = 0.021) and 1.8× in CAMLs (P = 0.004): however, individual patient PD-L1 expression varied, consistently low/negative (51%), consistently high (17%), or induced (31%).Conclusions: These data suggest that RAD50 foci formation in CTCs and CAMLs may be used to track cells subjected to radiation occurring at primary tumors, and following PD-L1 expression in circulating cells may be used as a surrogate for tracking adaptive changes in immunotherapeutic targets. Clin Cancer Res; 23(19); 5948–58. ©2017 AACR.

Supplementary Figure 1. Individual and expanded images of DAPI, Cytokeratin and CD45 from Figure 2. Supplementary Figure 2. Determining the thresholds for scoring PD-L1 expression in circulating cells. Supplementary Figure 3. Average PD-L1 and RAD50 changes in each individual patient before and after induction of radiotherapy, separated by cell type. Supplementary Figure 4. Confocal imaging of RAD50 within the nuclei of a cluster of EMTCTCs from Figure 1, imaged top to bottom. Supplementary Figure 5. Distribution of RAD50 foci in cells by stage and before treatment or after treatment. Supplementary Figure 6. Percent change in pixel intensity from the T0 time point to the T1 time point. Supplementary Table 1. Patient population overview Supplementary Table 2. Tracking the longevity of PD-L1 expression levels after completion of radiotherapy.

Purpose: HSP90 inhibition is well known to sensitize cancer cells to radiation. However, it is currently unknown whether additional radiosensitization could occur in the more clinically relevant setting of chemoradiation (CRT). We used the potent HSP90 inhibitor ganetespib to determine whether it can enhance CRT effects in NSCLC.Experimental Design: We first performed in vitro experiments in various NSCLC cell lines combining radiation with or without ganetespib. Some of these experiments included clonogenic survival assay, DNA damage repair, and cell-cycle analysis, and reverse-phase protein array. We then determined whether chemotherapy affected ganetespib radiosensitization by adding carboplatin–paclitaxel to some of the in vitro and in vivo xenograft experiments.Results: Ganetespib significantly reduced radiation clonogenic survival in a number of lung cancer cell lines, and attenuated DNA damage repair with irradiation. Radiation caused G2–M arrest that was greatly accentuated by ganetespib. Ganetespib with radiation also dose-dependently upregulated p21 and downregulated pRb levels that were not apparent with either drug or radiation alone. However, when carboplatin–paclitaxel was added, ganetespib was only able to radiosensitize some cell lines but not others. This variable in vitro CRT effect was confirmed in vivo using xenograft models.Conclusions: Ganetespib was able to potently sensitize a number of NSCLC cell lines to radiation but has variable effects when added to platinum-based doublet CRT. For optimal clinical translation, our data emphasize the importance of preclinical testing of drugs in the context of clinically relevant therapy combinations. Clin Cancer Res; 22(23); 5876–86. ©2016 AACR.

Purpose: The MEK inhibitor trametinib radiosensitizes KRAS-mutant non–small cell lung cancer (NSCLC) and is being tested clinically with chemoradiation. However, variability in response to trametinib suggests that additional pathways are involved. The mechanism of resistance to trametinib radiosensitization is still unknown.Experimental Design: We used a panel of KRAS-mutant NSCLC cells and tested the radiosensitization effects of trametinib by clonogenic survival assay. Then, we investigated the mechanisms underlying the resistance to the combination therapy through several knockout and overexpression systems. Finally, we validated our findings in syngeneic mouse models in a treatment setting that mimicked the standard of care in the clinic.Results: Radiosensitization by trametinib was effective only in KRAS-LKB1–mutated cells with wild-type (WT) p53, and we found that restoring LKB1 expression in those cells blocked that sensitization. Trametinib and radiotherapy both induced senescence in a p53-dependent manner, but in WT LKB1 cells, the combination also activated the AMPK-autophagy pathway to rescue damaged cells from senescence. LKB1-knockout or autophagy inhibition in WT LKB1 cells potentiated trametinib radiosensitization. In syngeneic animal models of Kras-mutant lung tumors, Lkb1-knockout tumors were resistant to trametinib and chemoradiation given separately, but the combination greatly controlled tumor growth and prolonged survival.Conclusions: The LKB1 mutation in KRAS-mutant NSCLC conferred enhanced radiosensitization in combination with trametinib. The WT LKB1 could activate autophagy through AMPK pathway to induce resistance to the combination of trametinib and radiation. The KRAS-LKB1 mutation could potentially be a biomarker to select patients for trametinib and radiotherapy combination therapy. Clin Cancer Res; 24(22); 5744–56. ©2018 AACR.

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Oligos for pLentiCRISPRv2 construction

PURPOSE Current diagnostic methods to determine programmed death 1 (PD-1) receptor and its ligand (PD-L1)/PD-1 immunotherapy (immune checkpoint inhibitor [ICI]) efficacy in recurrent or metastatic non–small-cell lung carcinoma (rmNSCLC) are imprecise. Although previously shown that patients with high tumor PD-L1 (≥ 50%) demonstrate clinical benefit in the form of disease reduction and improved survival, patients with low PD-L1 (< 50%) sometimes benefit from treatment. Since the PD-L1/PD-1 pathway is dynamic, monitoring PD-L1 levels during treatment may be more accurate than a static baseline tumor biopsy; however, rebiopsying the primary or metastatic disease is rarely feasible. Liquid biopsies that measure the upregulation of PD-L1 on tumor-associated cells (TACs), ie, cancer-associated macrophage-like cells and circulating tumor cells, have been performed, but their predictive value for ICI therapy efficacy is unknown. MATERIALS AND METHODS We initiated a single-blind prospective study to evaluate TAC PD-L1 expression changes in rmNSCLC from blood samples before (T0) and after (T1) treatment with ICI (ICI, n = 41) or without ICI (no ICI, n = 41). Anonymized blood was filtered to isolate TACs, which were then quantified for high/low PD-L1 expression. Progression-free survival (PFS) or overall survival (OS) hazard ratios (HRs) were evaluated at 18 and 24 months by censored univariate analysis. RESULTS Increased TAC PD-L1 expression between T0 and T1 in patients who were not treated with ICI had no relationship with PFS or OS. However, increased TAC PD-L1 expression between T0 and T1 in patients treated with ICI had significantly better PFS (HR, 3.49; 95% CI, 1.5 to 8.3; P = .0091) and OS (HR, 3.058; 95% CI, 1.2 to 7.9; P = .0410). CONCLUSION Blood-based monitoring of dynamic changes in PD-L1 in TACs appears to identify patients with rmNSCLC who may benefit from ICI.

We report radiatively coupled arrayed gold nanodisks on invisible substrate (AGNIS) as a cost-effective, high-performance platform for nanoplasmonic biosensing. By substrate undercut, the electric field distribution around the nanodisks has been restored to as if the nanodisks were surrounded by a single medium, thereby provides analyte accessibility to otherwise buried enhanced electric field. The AGNIS substrate has been fabricated by wafer-scale nanosphere lithography without the need for costly lithography. The LSPR blue-shifting behavior synergistically contributed by radiative coupling and substrate undercut have been investigated for the first time, which culminates in a remarkable refractive index sensitivity increase from 207 nm/RIU to 578 nm/RIU. The synergy also improves surface sensitivity to monolayer neutravidin-biotin binding from 7.4 nm to 20.3 nm with the limit of detection (LOD) of neutravidin at 50 fM, which is among the best label-free results reported to date on this specific surface binding reaction. As a potential cancer diagnostic application, extracellular vesicles such as exosomes excreted by cancer and normal cells were measured with a LOD within 112–600 (exosomes/ $\mu \text{L}$ ), which would be sufficient in many clinical applications. Using CD9, CD63, and CD81 antibodies, label-free profiling has shown increased expression of all three surface antigens in cancer-derived exosomes. This work demonstrates, for the first time, strong synergy of arrayed radiative coupling and substrate undercut can enable economical, ultrasensitive biosensing in the visible light spectrum where high-quality, low-cost silicon detectors are readily available for point-of-care applications.

BACKGROUND: Various methods of liquid biopsy through the sampling of blood in cancer patients allow access to minuscule amounts of tumor that can easily be sampled repeatedly throughout therapy. Circulating tumor cells (CTCs) represent shed tumor cells that can be characterized by imaging or molecular techniques using an amenable enrichment platform. Here we validate the Hitachi Chemical Micro Cavity Array (MCA) for the enrichment of CTCs from the blood of patients diagnosed with stage III non-small cell lung cancer (NSCLC). MCA is a semi-automated filtration system that enriches CTCs on the basis of size and membrane deformability rather than a biased selection of surface antigens. METHODS: CTCs were enriched from the peripheral blood of 38 patients diagnosed with stage III NSCLC at the start of chemoradiation. Two tubes of EDTA blood were collected from each patient and processed through MCA in parallel. In the first tube, CTCs were identified as pan-cytokeratin (CK)+ CD45− nucleated cells and enumerated. The second tube was depleted of leukocytes using CD45 antibody-coated magnetic microbeads before enrichment by MCA, followed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) to interrogate CTC-enriched lysates for expression of 16 target mRNAs from a panel of epithelial, mesenchymal, stem-like, and cancer signaling-related genes. CTC-enriched lysates from similarly prepared peripheral blood samples from 18 healthy donors were used to define positive gene expression. RESULTS: CTCs were identified by imaging in 30 of 38 patient samples (79%). At least 1 target gene was positively expressed in 23 of 25 (92%) patient samples that was subjected to molecular characterization. A CTC count of ≥7 was associated with poor progression-free survival (PFS) [hazard ratio (HR) 4.24, 95% confidence interval (CI), 1.73–10.40, P=0.020] and poor overall survival (HR 8.17, 95% CI, 2.87–23.26, P

Purpose: Cancer extracellular vesicles (EVs) are involved in cellular communication, tumor growth, progression, and metastasis in cancer. The origins of EVs, their formation, and potential clinical use as biomarkers are not well understood. Recently, budding of extracellular structures on Cancer Associated Macrophage-Like Cells [CAMLs] a specific subtype of phagocytic circulating stromal cells has been observed in metastatic non-small cell lung carcinoma (mNSCLC) patients. In this prospective analysis of n=40 mNSCLC samples, we enumerated EV budding on CAMLs to determine if their formation had an effect on clinical outcomes. These preliminary results suggest that EV budding from a specific subtype of circulating tumor associated macrophage prognosticates for worse clinical outcome which may serve as the mechanism for cancer EV formation and spread throughout the body. Patients and Methods: We initiated a single blind prospective pilot study to evaluate extracellular budding on the CAMLs of mNSCLC patients from blood samples obtained prior to therapy to determine their prevalence and clinical utility. Anonymized blood was procured and filtered to isolate CAMLs and stained for cytokeratin, CD45, CD31 and PD-L1. EV budding was observed as small (≤1 µm) bulbous protrusions from the cell periphery. EVs were quantified and compared against patient progression free survival (PFS) and overall survival (OS) with hazard ratios (HRs) at 24 months by censored univariate analysis. The imaged EVs were also characterized by their PD-L1 biomarker expression. Results: CAMLs were identified in 88% (n=35/40) of all samples, with EV budding identified in 60% (n=21/35) of CAMLs. These EVs appeared with tumor positive proteins (i.e. CD31, CD45, PD-L1 and cytokeratin). With a minimum of 24 months of follow-up, it was determined that the presence of EV budding in patients’ CAMLs was associated with significantly worse PFS (HR=4.00, 95%CI=1.4-12, p=0.0251) and borderline significant OS (HR=3.57, 95%CI=1.1-12, p=0.0747). Conclusions: EV budding found on phagocytic stromal cells found in the blood appear with tumor positive biomarkers and predict poor survival. These findings suggest that CAMLs are an origin cell for some cancer EVs. Larger validation studies and cross comparison of PD-L1 on EVs as it related to immunotherapy response is ongoing. Citation Format: Jillian A. Moran, Steven H. Lin, Martin J. Edelman, Pablo Lopez, Jianzhong He, Yawei Qiao, Ting Xu, Zhongxing Liao, Kirby P. Gardner, Cha-Mei Tang, Daniel L. Adams. Extracellular vesicles budding from stromal macrophages in the blood of metastatic non-small cell lung cancer patients correlates with poor survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3310.

Circulating tumor DNA (ctDNA) molecular residual disease (MRD) following curative-intent treatment strongly predicts recurrence in multiple tumor types, but whether further treatment can improve outcomes in patients with MRD remains unclear. We applied CAPP-Seq ctDNA analysis to 218 samples from 65 patients receiving chemoradiation therapy (CRT) for locally advanced NSCLC, including 28 patients receiving consolidation immune checkpoint inhibition (CICI). Patients with undetectable ctDNA after CRT had excellent outcomes whether or not they received CICI. Among such patients, one died from CICI-related pneumonitis, highlighting the potential utility of only treating patients with MRD. In contrast, patients with MRD after CRT who received CICI had significantly better outcomes than patients who did not receive CICI. Furthermore, the ctDNA response pattern early during CICI identified patients responding to consolidation therapy. Our results suggest that CICI improves outcomes for NSCLC patients with MRD and that ctDNA analysis may facilitate personalization of consolidation therapy.

Purpose The combination of cytotoxic chemotherapy with radiation therapy (CRT) has resulted in significant improvements in clinical outcomes for patients with many locally advanced unresectable cancers. Only a small proportion of patients achieve pathologic complete responses to CRT; combination of CRT with targeted agents offers the promise of further improving treatment responses. However, numerous clinical trials have failed to show an improvement in clinical outcomes with the addition of targeted agents. To increase the accessibility of our screening method and accelerate the pace at which novel combinations with CRT are identified and incorporated into standard practices for treatments, we report details on screening method optimization, data generation, and downstream data analysis. Methods In part, the gap in translation to large, expensive, and ultimately unsuccessful clinical trials reflects the shortcomings of inconsistently designed, executed, and reported preclinical data on which these studies are based. In an effort to standardize the selection of agents for future clinical testing, we have designed, optimized and validated a high throughput, high content, clonogenic assay platform for step-wise progression of preclinical studies from in vitro to in vivo in non-small cell lung cancer and pancreatic ductal adenocarcinoma. Results This highly stable in vitro method was standardized for identification of the most promising CTEP drugs that could best be combined with CRT from among as screen of multiple agents tested in an unbiased manner using 96-well plates. The methodology lends itself to seamless testing of multiple agents in a similar fashion allowing cross-comparisons, evaluation of CRT, or radiation therapy alone, and testing multiple concentrations of test agents sequenced at different times before and after radiation. The method identified Trametinib as a strong CRT sensitizer in KRAS-mutant non-small cell lung cancer and pancreatic ductal adenocarcinoma cell lines. This platform has enabled the screening and identification of several chemoradiation sensitizers.Conclusions: High throughput, high content clonogenic drug screening assay allows for the rapid identification of targets and agents to be translated to the clinic to help improve the effectiveness of current standard of care CRT in various solid tumors.

Chemoradiation (CRT) is widely used to treat locally advanced non-small cell lung cancer (NSCLC) patients, but only around 30% of patients achieve pathological complete response. Here, we utilized an in vitro high-content clonogenic survival screening method to identify CRT sensitizers from the NCI Cancer Therapy Evaluation Program (CTEP) portfolio. Talazoparib (PARPi) was identified among the top candidates to show potent CRT sensitization effects in both KRAS mutant and TP53 mutant NCSLC cell lines. We validated the CRT sensitization effect of PARPi on lung tumors in vivo with cell line xenografts mouse models. To further investigate alterations in the tumor microenvironment (TME) induced by PARPi, we utilized syngeneic mouse models and showed that the combination of radiotherapy, PARPi, and PD-L1 blockade achieved superior tumor control effects. By applying single cell RNA sequencing technologies to the mouse tumors, we found that PARPi combined with CRT or immunotherapy significantly reprogrammed the tumor cells and TME, resulting in the increase of tumor-infiltrating T cells which elicit potent tumor control effects. Our data showed that PARPi sensitizes NSCLC tumors to CRT and immunotherapy through a combination of tumor-intrinsic and extrinsic phenomenon. Citation Format: Rui Ye, Kaile Wang, Yawei Qiao, Zhenna Xiao, Yun Yan, Jianzhong He, Nan Li, Yifan Wang, Min Hu, Shanshan Bai, Emi Sei, Nicholas Navin, Steven Lin. Chemoradiation sensitization effect of PARPi in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3308.

3054 Background: Circulating stromal cells, ie Cancer Associated Macrophage-Like cells (CAMLs), are prevalent in the circulation of non-small cell lung carcinoma (NSCLC) patients (pts), appearing as giant phagocytic macrophages that represent an inflammatory pro-tumorigenic microenvironment. Previously it was shown that pts with engorged CAMLs of ≥50µm after treatment are prognostic for poor clinical outcomes. However, analyzing the dynamic changes in CAMLs over time or in response to treatment, ie chemoradiation (CRT) and immunotherapy (IMT) has not been evaluated. We monitored n = 182 unresectable NSCLC stage II/III pts treated with CRT alone (n = 91) or with concurrent IMT (n = 91) to evaluate changes in CAMLs before and after CRT induction at it relates to progression free survival (PFS) or overall survival (OS). Methods: We prospectively procured pts from 3 different regimes, treated with CRT alone (n = 91), treated concurrently with CRT & Atezolizumab (n = 40, clinical trial NCT02525757), or treated concurrently with Durvalumab (n = 51). We recruited 182 pts with pathologically confirmed stage II/III unresectable NSCLC. A total of 15 mL blood samples were drawn prior to start of therapy at baseline (BL) and ̃5 weeks (T1) after CRT induction. Blood filtration was done using CellSieve filters, then CAMLs were identified and measured to evaluate PFS & OS hazard ratios (HRs) by censored univariate and multivariate analyses at 2 years. Results: CAMLs were found in 89% of all samples tested. Increases in CAML size between BL & T1 were significantly correlated with worse clinical outcomes, with higher CAML increases correlated with increasingly worse outcomes, including CAML increases >10μm resulting in PFS HR=1.7 p = 0.027 & OS HR=1.9 p = 0.045, through increases >40μm resulting in PFS HR=2.1 p = 0.013 & OS HR=2.5 p = 0.020. Increases of CAMLs >35μm was optimal at stratifying pts PFS HR=2.2 p = 0.005 & OS HR=2.8 p = 0.005. Specifically, pts treated with only CRT and increasing CAMLs >35μmhad significantly worse PFS HR=2.7 p = 0.029 & OS HR=4.1 p = 0.013. In parallel, pts treated with CRT+IMT and increasing CAMLs >35μm had near significance for worse PFS (HR=2.1 p = 0.073) & OS (HR=2.3, p = 0.147), though follow up clinical data is ongoing. Conclusions: Our data suggest that in unresectable stage II/III NSCLC, tracking the increase of pro inflammatory immune cells (CAMLs) in circulation during therapy induction can identify pts less responsive to CRT or PD-L1/PD-1 IMTs.

8535 Background: Cancer Associated Macrophage Like cells (CAMLs), a circulating stromal cell found in cancer patients (pts) blood, are phagocytic giant macrophages that appear to parallel the inflammatory PD-L1 state of the tumor microenvironment. Previously, we demonstrated in local non-small cell lung carcinoma (NSCLC), CAML PD-L1 expression is dynamic and predicts response to PD-L1/PD-1 immunotherapies (IMTs) following sequential sampling before and after chemotherapy (chemo) induction (̃30days) based on progression free (PFS) & overall survival (OS). However this has not been tested in metastatic NSCLC (mNSCLC). Here,we report the results of monitoring PD-L1 expression in CAMLs before and after chemo induction (̃30 days) to evaluate its predictive value in mNSCLC pts treated with or without IMT. Methods: A single blind multi-year prospective study was undertaken to test the relationship of PD-L1 expression in CAMLs to PFS & OS, pre & post chemo induction, in recurrent mNSCLC with (n = 41) or without (n = 41) additional anti-PD-L1/PD-1 IMTs. This included three IMTs: atezolizumab (n = 4), nivolumab (n = 8) or pembrolizumab (n = 29). We recruited 82 pts with pathologically confirmed recurrent mNSCLC prior to treatment for newly recurrent metastatic disease. Blood samples (15 mL) were taken at Baseline (BL), prior to chemo, and ̃30 days after chemotherapy (T1). Blood was filtered by CellSieve filtration & CAMLs’ expression scored as a binary high/low, to evaluate PFS & OS hazard ratios (HRs) by censored univariate & multivariate analysis at 18 months. Results: CAMLs were found in 97% of all tested samples, 94% at BL & 100% at T1. CAML PD-L1 at BL was found not to be associated with PFS or OS in pts treated with chemo alone (PFS p = 0.620 & OS p = 0.673) or chemo+IMT (PFS p = 0.353 & OS = 0.477) at 18 months. At T1, high CAML PD-L1 in pts treated with chemo alone had no significantly different PFS (HR = 1.3, p = 0.694) or OS (HR = 1.6 p = 0.503). However, high CAML PD-L1 at T1 in pts treated with chemo+IMT had significantly better PFS (HR = 3.1, 95%CI = 1.3-7.3, p = 0.019), and OS (HR = 3.4, 95%CI = 1.4-8.3, p = 0.014). Further subtyping & analysis is ongoing to evaluate PFS and OS at 24 months. Conclusions: Our data suggests that in mNSCLC, PD-L1 expression in circulating CAMLs dynamically upregulates after induction with chemotherapy and appears to predict patients with increased benefit to PD-L1/PD-1 IMTs, though additional studies are needed to validate these findings.

Background Cancer Associated Macrophage-Like cells (CAMLs) are polynucleated circulating stromal cells found in the bloodstream of numerous solid-tumor malignancies. Variations within CAML size have been associated with poorer progression free survival (PFS) and overall survival (OS) in a variety of cancers; however, no study has evaluated their clinical significance in esophageal cancer (EC). Methods To examine this significance, we ran a 2 year prospective pilot study consisting of newly diagnosed stage I-III EC patients (n = 32) receiving chemoradiotherapy (CRT). CAML sizes were sequentially monitored prior to CRT (BL), ~ 2 weeks into treatment (T1), and at the first available sample after the completion of CRT (T2). Results We found CAMLs in 88% (n = 28/32) of all patient samples throughout the trial, with a sensitivity of 76% (n = 22/29) in pre-treatment screening samples. Improved 2 year PFS and OS was found in patients with CAMLs p = 0.004) and OS (HR = 9.0, 95%CI = 1.9–43.5, p = 0.019). Conclusions Tracking CAML sizes throughout CRT as a minimally invasive biomarker may serve as a prognostic tool in mapping EC progression, and further studies are warranted to determine if presence of these cells prior to treatment suggest diagnostic value for at-risk populations.

Background Cancer-associated macrophage-like cells (CAMLs) are a potential peripheral blood biomarker for disease progression. This study used data from a phase 2 clinical trial to evaluate prognostic utility of CAMLs for locally advanced non–small-cell lung cancer treated with definitive chemoradiotherapy (CRT) and atezolizumab (DETERRED; ClinicalTrials.gov NCT02525757 ). Patients and Methods Sample collection occurred at baseline (T0), during CRT (T1), at end of CRT (T2), and at first follow-up (T3). CAMLs were captured and quantified by the CellSieve system using multiplex immunostaining. Giant CAMLs were defined as characteristic CAMLs ≥ 50 μm. Kaplan-Meier methodology estimated progression-free survival, distant failure-free survival, relapse-free survival, and overall survival at 30 months. Results Thirty-nine patients were evaluated between December 2015 and March 2018. Median follow-up was 27 months. Most disease was stage III (85%) and comprised squamous-cell carcinoma (38%) or adenocarcinoma (59%). In total, 267 blood samples were analyzed. Giant CAMLs were identified in 57%, 60%, 64%, and 63% of patients at T0, T1, T2, and T3, respectively. Patients with giant CAMLs at T3, occurring at a median of 30 days after completion of CRT, had significantly worse distant failure-free survival (hazard ratio [HR] 4.9, P = .015), progression-free survival (HR 2.5, P = .025), recurrence-free survival (HR 2.4, P = .036), and overall survival (HR 3.5, P = .034) compared to patients with small or no CAMLs. Conclusions Presence of giant CAMLs after CRT completion was associated with development of metastatic disease and poorer survival despite the use of maintenance immunotherapy. Monitoring CAMLs may help risk-stratify patients for adaptive treatment strategies.

Purpose: The MEK inhibitor trametinib radiosensitizes KRAS-mutant non–small cell lung cancer (NSCLC) and is being tested clinically with chemoradiation. However, variability in response to trametinib suggests that additional pathways are involved. The mechanism of resistance to trametinib radiosensitization is still unknown.Experimental Design: We used a panel of KRAS-mutant NSCLC cells and tested the radiosensitization effects of trametinib by clonogenic survival assay. Then, we investigated the mechanisms underlying the resistance to the combination therapy through several knockout and overexpression systems. Finally, we validated our findings in syngeneic mouse models in a treatment setting that mimicked the standard of care in the clinic.Results: Radiosensitization by trametinib was effective only in KRAS-LKB1–mutated cells with wild-type (WT) p53, and we found that restoring LKB1 expression in those cells blocked that sensitization. Trametinib and radiotherapy both induced senescence in a p53-dependent manner, but in WT LKB1 cells, the combination also activated the AMPK-autophagy pathway to rescue damaged cells from senescence. LKB1-knockout or autophagy inhibition in WT LKB1 cells potentiated trametinib radiosensitization. In syngeneic animal models of Kras-mutant lung tumors, Lkb1-knockout tumors were resistant to trametinib and chemoradiation given separately, but the combination greatly controlled tumor growth and prolonged survival.Conclusions: The LKB1 mutation in KRAS-mutant NSCLC conferred enhanced radiosensitization in combination with trametinib. The WT LKB1 could activate autophagy through AMPK pathway to induce resistance to the combination of trametinib and radiation. The KRAS-LKB1 mutation could potentially be a biomarker to select patients for trametinib and radiotherapy combination therapy. Clin Cancer Res; 24(22); 5744–56. ©2018 AACR.

PURPOSE/OBJECTIVE(S) Cancer Associated Macrophage-Like cells (CAMLs) are a type of circulating stromal cell found in the blood of cancer patients (pts), described as of myeloid origin that represent the inflammatory state of the tumor microenvironment. We have previously reported that in non-small cell lung carcinoma (NSCLC), CAML PD-L1 expression is dynamic and trackable throughout chemoradiation (CRT). However, it is unknown if PD-L1 on CAMLs has clinical utility, particularly in immunotherapy (IMT) efficacy after CRT. We studied stage 3 unresectable NSCLC pts treated with (n = 80) or without (n = 55) IMT agents after CRT to evaluate CAML PD-L1 expression on progression free survival (PFS) & overall survival (OS). MATERIALS/METHODS We used 2 sets of IMT treated pts: first set from a single arm phase 2 trial treated with CRT and atezolizumab (atezo) (n = 34) and a second from a multi-year prospective study treated with standard of care CRT with consolidation durvalumab (durva) (n = 46). A control group of CRT alone pts (n = 55) were evaluated during the same period (majority before 2018). In all, 135 pts with pathologically confirmed unresectable stage 3 NSCLC were included. 15mL blood samples were taken at Baseline (BL) & ∼1 month after completion of CRT. Blood was filtered & CAMLs quantified for PD-L1 expression using a binary score (0/1 = low & 2/3 = high), to evaluate PFS & OS hazard ratios (HRs) by censored univariate & multivariate analysis at 24 months. RESULTS CAMLs were found in 92% of all samples, on average 5.2 CAMLs/15mL. From the available tumor biopsies, > 1% PD-L1 expression using DAKO 22c3 did not predict CRT+IMT (atezo/durva) response (PFS HR 1.4 P = 0.642 & OS HR 1.9 P = 0.293). At BL, high CAML PD-L1 was not associated with PFS in CRT alone (HR 1.5 P = 0.435), CRT+atezo (HR 1.0 P = 0.843), or CRT+durva (HR 1.6 P = 0.6180). After CRT, while high CAML PD-L1 did not predict PFS in CRT alone (HR 1.0 P = 0.925), it was associated with superior PFS in CRT+atezo (HR 2.8 P = 0.046), & CRT+durva (HR 5.2 P = 0.036). For OS, high CAML PD-L1 was not predictive of outcomes in CRT alone (HR 0.8 P = 0.929), but strongly predictive of superior OS for CRT+atezo (HR 4.3 P = 0.036) & CRT+durva (HR 5.9 P = 0.033) groups. Combined (atezo or durva, n = 80), 57% of pts had either maintained high PD-L1 before and after CRT (N = 25) or increased from BL (N = 21). Pts with high PD-L1 post CRT had better outcomes than pts with low expression, PFS HR = 4.1 P < 0.001 and OS HR = 4.7 P < 0.001. This pattern was not seen in pts treated with CRT alone (PFS HR = 1.2 P = 0.763 and OS HR = 0.9 P = 0.977). CONCLUSION Our data suggests that in unresectable stage 3 NSCLC, high PD-L1 expression on CAMLs after CRT completion is predictive of superior clinical outcomes in pts treated with IMT, but not in those treated with CRT alone. Prospective validation is needed to confirm these findings.

Microdroplet single-cell ATAC-seq is widely used to measure chromatin accessibility, however, highly scalable and simple sample multiplexing procedures are not available. Here, we present a transposome-assisted single nucleus barcoding approach for ATAC-seq (SNuBar-ATAC) that utilizes a single oligonucleotide adaptor for multiplexing samples during the existing tagmentation step and does not require a pre-labeling procedure. The accuracy and scalability of SNuBar-ATAC was evaluated using cell line mixture experiments. We applied SNuBar-ATAC to investigate treatment-induced chromatin accessibility dynamics by multiplexing 28 mice with lung tumors that received different combinations of chemo, radiation, and targeted immunotherapy. We also applied SNuBar-ATAC to study spatial epigenetic heterogeneity by multiplexing 32 regions from a human breast tissue. Additionally, we show that SNuBar can multiplex single cell ATAC and RNA multiomic assays in cell lines and human breast tissue samples. Our data show that SNuBar is a highly accurate, easy-to-use, and scalable system for multiplexing scATAC-seq and scATAC and RNA co-assay experiments.

Purpose: Evidence suggests that PD-L1 can be induced with radiotherapy and may be an immune escape mechanism in cancer. Monitoring this response is limited, as repetitive biopsies during therapy are impractical, dangerous, and miss tumor stromal cells. Monitoring PD-L1 expression in both circulating tumor cells (CTCs) and circulating stromal cells (CStCs) in blood-based biopsies might be a practical alternative for sequential, noninvasive assessment of changes in tumor and stromal cells. Experimental Design: Peripheral blood was collected before and after radiotherapy from 41 patients with lung cancer, as were primary biopsies. We evaluated the expression of PD-L1 and formation of RAD50 foci in CTCs and a CStC subtype, cancer-associated macrophage-like cells (CAMLs), in response to DNA damage caused by radiotherapy at the tumor site. Results: Only 24% of primary biopsies had sufficient tissue for PD-L1 testing, tested with IHC clones 22c3 and 28-8. A CTC or CAML was detectable in 93% and 100% of samples, prior to and after radiotherapy, respectively. RAD50 foci significantly increased in CTCs (>7×, P < 0.001) and CAMLs (>10×, P = 0.001) after radiotherapy, confirming their origin from the radiated site. PD-L1 expression increased overall, 1.6× in CTCs (P = 0.021) and 1.8× in CAMLs (P = 0.004): however, individual patient PD-L1 expression varied, consistently low/negative (51%), consistently high (17%), or induced (31%). Conclusions: These data suggest that RAD50 foci formation in CTCs and CAMLs may be used to track cells subjected to radiation occurring at primary tumors, and following PD-L1 expression in circulating cells may be used as a surrogate for tracking adaptive changes in immunotherapeutic targets. Clin Cancer Res; 23(19); 5948–58. ©2017 AACR.

Additional file 1. Supplementary tables.

8534 Background: Cancer Associated Macrophage-Like cells (CAMLs) are circulating stromal cells in the blood of patients (pts) with solid tumors that are phagocytic macrophages that may represent the inflammatory state of the tumor microenvironment. Previously, we demonstrated CAMLs ≥50µm after chemo-radiation therapy (CRT) in NSCLC is associated with worse progression free survival (PFS) and overall survival (OS). We also showed that PDL1 expression in CAMLs is dynamic & can change with CRT, difficult to assess with repeat biopsies, but possible with liquid biopsy. For this study we evaluated whether CAML properties can predict response to CRT with/without immunotherapy (IMT) agents in unresectable NSCLC. Methods: A single blind multi-year prospective study was undertaken to test the relationship of PDL1 expression and ≥50µm CAML size to PFS/OS in NSCLC, pre and post CRT with (n = 96) and without (n = 72) anti-PDL1/PD1 IMT. This included atezolizumab (prospective single arm NCT02525757) n = 39, durvalumab n = 52 or pembrolizumab n = 5 both after 2018 FDA approval. We recruited 168 pts with pathologically confirmed unresectable NSCLC prior to CRT. Blood samples 15 mL were taken at baseline (BL), CRT completion (T1), and ̃1 month after CRT (T2) (with n = 96 or without n = 72 IMT). Blood was filtered by CellSieve filtration and CAMLs quantified for size ( < 49 µm or ≥50 µm) and PDL1 expression to evaluate PFS and OS hazard ratios (HRs) by censored univariate and multivariate analysis at 24 months. Results: CAMLs were found in 90% of all samples, average 5.8 CAMLs/15mL. At BL, ≥50µm CAMLs did not predict PFS in CRT/IMT pts (HR 1.6, p = 0.220) nor CRT alone (HR 1.3, p = 0.593). However, after completion of CRT (T1) ≥50µm CAMLs predicted PFS in CRT/IMT pts (HR 2.7, p = 0.003) and CRT alone (HR 2.5, p = 0.015). In primary tumor biopsies, PDL1 expression > 1% did not predict CRT/IMT response (PFS HR 1.8, p = 0.262 & OS HR 2.3, p = 0.158). At BL, high CAML PDL1 did not predict PFS in CRT/IMT pts (HR 1.4, p = 0.427) nor CRT alone (HR 1.1, p = 0.982). Further, at CRT completion (T1), high CAML PDL1 only trended for better PFS in CRT/IMT pts (HR 1.7, p = 0.137), but not CRT alone (HR 1.1, p = 0.972). At T2, however, pts with continuously high CAML PDL1 had significantly better PFS with IMT (HR 3.2, p = 0.002) vs CRT alone (HR 1.4, p = 0.616). While ≥50µm CAMLs at BL did not predict 24 month progression, ≥50 µm CAMLs after CRT (with or without 1 cycle of anti-PDL1 IMT) was 84% accurate at predicting progression. Further subtyping and analysis is ongoing to evaluate OS and PDL1 in the CAML populations. Conclusions: Our data suggests that in unresectable NSCLC, ≥50 µm CAMLs after completion of CRT is prognostic regardless of IMT use. PDL1 expression in CAMLs also appears to predict for response to consolidated IMT after CRT. Additional studies are needed to validate these findings.

8533 Background: Lung cancer is the leading cause of cancer death world-wide, and chemotherapy and radiation remain backbones of therapy for patients with locoregionally advanced and metastatic disease. However, the genetic mechanisms that mediate resistance to chemotherapy and radiation are largely unclear due to a lack of available tissue at the time of relapse. We hypothesized that circulating tumor DNA (ctDNA) analysis could identify emergent mutations after chemotherapy and radiation that may lead to treatment resistance. Methods: To identify emergent mutations at the time of progression following an initial response to chemotherapy and/or radiation therapy for lung cancer, we utilized CAncer Personalized Profiling by deep Sequencing (CAPP-Seq) to analyze plasma samples and matched leukocytes collected pre-treatment and at the time of relapse. We analyzed a targeted panel enriched for lung cancer drivers and recurrently mutated genes for 27 patients treated with chemoradiation therapy for locoregionally advanced lung cancer. In addition, we performed ultra-deep whole exome sequencing ( > 2000X deduped depth) of pre-treatment and relapse cell-free DNA for 5 patients treated with combination chemotherapy for metastatic lung cancer. Functional enrichment analysis was performed on emergent mutation gene lists to identify significantly enriched pathways. Results: We identified emergent variants in 6 out of 27 patients using targeted sequencing after chemoradiation therapy. Emergent mutations after chemoradiation were enriched for plasma membrane adhesion molecules such as PCDH17, PCDH10, and FAT3 (adjusted P = 0.03). Using ultra-deep whole exome sequencing, we observed emergent mutations in 3 out of 5 patients treated with combination chemotherapy. After combination chemotherapy, there was a trend towards enrichment in mutations in ATP-binding cassette transporters, including ABCA13 and ABCB4 (adjusted P = 0.057). Notably, there were no recurrent emergent mutations within our cohort. Conclusions: Our results suggest that ultra-deep whole exome sequencing can non-invasively identify emergent mutations at the time of progression. Resistance to cytotoxic therapy is likely multi-factorial and analysis in expanded cohorts will be helpful to identify recurrently mutated pathways that may contribute to disease progression after an initial response to therapy.

Introduction: Despite evidence that a subset of patients with locoregionally advanced non-small cell lung cancer (NSCLC) can be cured with radiation doses less than 60 Gy, there are currently no validated approaches to identify patients that could benefit from radiation dose de-escalation. Normal tissue changes including inflammation and fibrosis can be difficult to distinguish from residual disease on standard imaging during and following chemoradiation therapy (CRT), making assessment of treatment response and identification of favorable responders challenging. We hypothesized that circulating tumor DNA (ctDNA) kinetics during CRT could be used as a surrogate of response to identify genomic predictors of rapid response to treatment. Methods: We applied cancer personalized profiling by deep sequencing (CAPP-Seq) ctDNA analysis to 61 patients treated with CRT for Stage II-III NSCLC. We quantified ctDNA concentrations pre-CRT and a median of 21 days into CRT (mid-CRT) to determine the log-fold change in ctDNA concentration and identify “rapid responders.” The association between ctDNA log-fold change as a continuous variable with progression-free survival (PFS) was analyzed using univariable and multivariable regression, including gender, age, and stage as co-variables. The prevalence of driver gene single nucleotide variants in rapid responders versus slow responders was compared for each gene using Fisher’s exact tests with P-values adjusted using the Benjamini-Hochberg procedure. Results: Mid-CRT ctDNA log-fold change was significantly associated with progression-free survival as a continuous variable on both univariable (P=0.02) and multivariable analysis (P=0.03). Among patients whose ctDNA log-fold change was more negative than -2.15, 10/11 (91%) did not recur within the radiation field. We defined ctDNA rapid responders as the 10 patients with the largest decrease in ctDNA concentration mid-CRT without local progression. Compared with slow responders, ctDNA rapid responders had a trend towards more TP53 mutations (P=0.12), but no driver mutations were significantly enriched in rapid responders. Notably, mutations in common driver genes KEAP1, NFE2L2, KRAS, and EGFR were observed in 36% of slow responders and 0% of rapid responders (P=0.03). Conclusions: Our results suggest that ctDNA kinetics during CRT can identify patients responding favorably to treatment. Additional molecular characterization of ctDNA rapid responders may enable identification of patients who could benefit from treatment de-escalation. Citation Format: Everett J. Moding, Yufei Liu, Angela B. Hui, Jianzhong He, Yawei Qiao, Ting Xu, Luyang Yao, Saumil Gandhi, Zhongxing Liao, Millie Das, Kavitha J. Ramchandran, Sukhmani K. Padda, Joel W. Neal, Heather A. Wakelee, Billy W. Loo, Steven H. Lin, Ash A. Alizadeh, Maximilian Diehn. Circulating tumor DNA kinetics to identify genomic predictors of rapid response to chemoradiation in non-small cell lung cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-069.

Background: Circulating stromal cells (CStCs) have been found to be common in the peripheral blood of cancer patients and hypothesized to be a blood based biomarker for monitoring cancer treatment. It has previously been described that the dynamic changes of PD-L1 expression during chemoradiotherapy (CRT) could be tracked using circulating stromal cells. However, how these changes relate to PD-L1/PD-1 immunotherapy (IMT) response is unstudied. We prospectively monitored PD-L1 expression in 2 cell types found in circulation (Circulating Tumor Cells [CTCs] and Cancer Associated Macrophage-like Cells [CAMLs]) in locally advanced non-small cell lung cancer (NSCLC) patients (pts) treated with Atezolizumab (Atezo) after definitive CRT (n=39) or in pts with CRT alone (n=40). Methods: A 2 year single blind prospective study was undertaken in pts with locally advanced NSCLC in 40 patients treated with CRT alone, or from a phase II DETERRED trial (NCT02525757) where Atezo was added for 1 year after completing CRT (n=10), or concurrently and after CRT (n=30). Samples from 39 of 40 pts from the DETERRED study were available for analysis. Baseline blood samples (7.5 ml) were drawn prior to start of CRT (T0), and a second sample was drawn ~1 month after completing CRT (T1), but prior to induction of Atezo. Blood was processed by CellSieve™ microfilters; stained for cytokeratin/PDL1/CD45 to identify CTCs and CAMLs. PD-L1 intensity was measured and grouped by 4 scores: 0-negative, 1-low, 2-medium, & 3-high. PD-L1 levels from circulating cells were used to evaluate PFS and OS. Significance was assessed by log-rank testing. Results: At least one CTC and/or CAML was found in 91% of available T0 samples and 96% of available T1 samples. In the 40 patients that received CRT alone, 35 pts had measurable cells at T0 and PD-L1 expression in CStCs was low (0-1) in 20 pts and high (2-3) in 15 pts. Further, at T1 PD-L1 expression in CStCs was low in 12 pts and high in 28 pts, with no relationship to PFS (T0 HR=1.1, 95%CI 0.5-2.8, p=0.96 and T1 HR=0.8, 95%CI 0.3-2.0, p=0.82) or OS (T0 HR=0.8, 95%CI 0.2-2.8, p=0.99 and T1 HR=1.1, 95%CI 0.3-3.5, p=0.84). In the patient arm that received Atezo at T0, PD-L1 expression in CStCs was low in 21 pts and high in 17 pts, with no relationship to PFS (HR=0.5, 95%CI 0.2-1.7, p=0.18) or OS (HR=1.6, 95%CI 0.4-6.0, p=0.75). However at T1, pts with high PD-L1 had significantly improved PFS response to Atezo (HR 5.4, 95%CI 1.7-17.0, p=0.009), and improved OS (HR 21.5, 95%CI 4.5-91.9, p Conclusions: PD-L1 expression in tissue is often not used in IMT treatment decisions due to limited correlation with clinical responses. However, it has been suggested that sequential monitoring of PD-L1 expression in circulating stromal cells in blood may predict for patients who will respond to IMT. These data suggests that CRT altered PD-L1 expression, and monitoring dynamic changes of PD-L1 in CStCs may predict immunotherapy effectiveness in NSCLC after CRT. Citation Format: Daniel L. Adams, Jianzhong He, Yawei Qiao, Kirby P. Gardner, John V. Haymach, Anne S. Tsao, Ashvathi Raghavakaimal, Cha-Mei Tang, Alexander Augustyn, Steven H. Lin. Expression of pd-l1 on circulating stromal cells predicts immunotherapy response in unresectable non-small cell lung carcinoma after definitive chemoradiotherapy [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 3297.

9046 Background: Circulating tumor DNA (ctDNA) molecular residual disease after curative intent therapy predicts disease progression in localized lung cancer. We hypothesized that integrating pre-CRT features and ctDNA levels during chemoradiation therapy (CRT) can predict patient outcomes earlier to enable response-adapted therapy. Methods: We identified pre-CRT features prognostic of disease progression after CRT for Stage II-III non-small cell lung cancer (NSCLC) in a historical “pre-CRT” training cohort of 109 patients. In addition, we applied CAPP-Seq ctDNA analysis pre-CRT and a median of 21 days into CRT (mid-CRT) to a “ctDNA” training cohort of 42 patients treated at MD Anderson and an independent validation cohort of 21 patients treated at Stanford. Prognostic pre-CRT features and mid-CRT ctDNA concentration were integrated using a Bayesian proportional hazards approach to generate a Continuous Individualized Risk Index (Kurtz et al. Cell 2019) for NSCLC (CIRI-NSCLC) to predict freedom from progression (FFP). Results: Adenocarcinoma histology (HR 2.6, P = 0.0005) and KEAP1 mutation (HR 2.7, P = 0.002) but not stage (P = 0.16), age (P = 0.60), or gender (P = 0.98) were significantly associated with FFP in the pre-CRT training cohort. Mid-CRT ctDNA concentration as a continuous variable was significantly associated with FFP in the ctDNA training cohort (HR 1.6, P = 0.04), and applying an optimal threshold identified in the training cohort (3.2 hGE/ml) significantly stratified FFP in the independent ctDNA validation cohort (HR 4.8, P = 0.02). CIRI-NSCLC enabled individualized real-time updating of the probability of FFP as model features became available over the course of CRT. CIRI-NSCLC outperformed individual model features in the independent validation cohort when compared by C-statistic (CIRI-NSCLC: 0.85; mid-CRT ctDNA: 0.76; histology: 0.66; KEAP1: 0.60). Across the whole cohort, patients with a greater than 66% risk of progression predicted by CIRI-NSCLC (n = 10) had an FFP of 10.0% at 12 months while patients with a less than 33% risk of progression predicted by CIRI-NSCLC (n = 22) had an FFP of 79.7% at 12 months (HR 15.0, P < 0.001). Conclusions: Our results suggest that CIRI-NSCLC can identify patients at very high and low risk of progression. Prospective evaluation will be necessary to test the potential utility of adapting treatment based on CIRI-NSCLC.

3051 Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common in the peripheral blood of patients with solid tumors. In non-small cell lung carcinoma (NSCLC), patients with CAMLs ≥50µm after completion of chemoradiation therapy (CRT) have been shown to have worse progression free survival (PFS). However, with the recent addition of anti-PD-L1 therapies in conjunction with CRT as standard of care, it has never yet to be evaluated whether CAMLs remain predictive for monitoring progression in NSCLC patients post anti-PD-L1 therapy. Methods: A 2 year single blind prospective study was undertaken to test the relationship of ≥50µm CAMLs to PFS based on imaging in lung patients before and after induction of CRT and PD-L1. We recruited 104 patients with pathologically confirmed unresectable NSCLC Stage II (n = 14), Stage III (n = 83), Stage IV (n = 3), and locally recurrent disease (n = 4). Baseline (BL) blood samples were taken prior to start of therapy. A second time point blood sample (T1) was taken at the end of radiotherapy (~40 days). A third time blood sample (T2) was taken after induction of anti-PD-L1 therapy (e.g. Imfinizi, Keytruda, etc.). Blood was filtered by CellSieve filtration and CAMLs were quantified. Analysis by CAML size of < 49 µm or ≥50 µm was used to evaluate PFS hazard ratios (HRs) by censored univariate & multivariate analysis. Results: CAMLs were found in 87% of samples averaging 2.9 CAMLs/7.5mL sample. At BL, CAMLs ≥50 µm had similar PFS to patients with < 50 µm CAMLs (HR = 1.1 95%CI 0.6-1.95 p = 0.8661). However, after CRT (T1), patients with CAML size ≥50 µm had worse PFS (HR = 3.2, 95%CI 1.8-5.8 p = 0.0002). After induction of anti-PD-L1 therapy (T2), patients with ≥50 µm CAMLs also had worse PFS (HR = 2.8 95%CI 1.5-5.4 p = 0.0037). CAML size at BL was not accurate at predicting progression within 24 months; however ≥50 µm CAMLs after CRT or after 1 cycle of anti-PDL1 therapy was 71% accurate at predicting progression of disease. Conclusions: Our data suggests that in NSCLC, ≥50 µm CAMLs after completion of CRT or appearing after induction of anti-PD-L1 therapy appears to predict progressive disease. If validated, additional studies are needed to determine if CAMLs can serve as a significantly prognostic blood based marker for predicting survival in NSCLC patients early in the treatment regime.

BACKGROUND & AIMS: Biomarkers are needed to identify patients at risk of tumor progression following chemoradiotherapy for localized esophageal cancer. These could improve identification of patients at risk for cancer progression and selection of therapy. METHODS: We performed deep sequencing (CAPP-Seq) analyses of plasma cell-free DNA collected from 45 patients before and after chemoradiotherapy for esophageal cancer, as well as DNA from leukocytes, and fixed esophageal tumor biopsies collected during esophagogastroduodenoscopy. Patients were treated from May 2010 through October 2015; 23 patients subsequently underwent esophagectomy and 22 did not undergo surgery. We also sequenced DNA from blood samples from 40 healthy individuals (controls). We analyzed 802 regions of 607 genes for single-nucleotide variants previously associated with esophageal adenocarcinoma or squamous cell carcinoma. Patients underwent imaging analyses 6–8 weeks after chemoradiotherapy and were followed for 5 years. Our primary aim was to determine whether detection of circulating tumor DNA (ctDNA) following chemoradiotherapy is associated with risk of tumor progression (growth of local, regional, or distant tumors, detected by imaging or biopsy). RESULTS: The median proportion of tumor-derived DNA in total cell-free DNA before treatment was 0.07%, indicating that ultrasensitive assays are needed for quantification and analysis of ctDNA from localized esophageal tumors. Detection of ctDNA following chemoradiotherapy was associated with tumor progression (hazard ratio, 18.7; P

Background: Cancer Associated Macrophage-Like cells (CAMLs) are recently described circulating stromal cells common in the peripheral blood of cancer patients hypothesized to be a mechanism in cancer pathogenesis. We previously described that treatment naive patients with circulating CAMLs ≥50µm is a significant independent prognostic indicator of shorter progression free survival (PFS) in a variety of cancers. However, the clinical value of CAMLs in specific diseased cohorts for predicting response to treatment has not been evaluated. We present the results of a prospective study on treatment naive lung cancer patients before induction and directly after completion of definitive radiotherapy to determine if CAMLs are predictive of treatment response and cancer progression. Methods: A 2 year single blind prospective study was undertaken, testing the relationship of enlarged CAMLs (≥50µm) to PFS of lung cancer patients before & after induction of definitive radiation therapy. To achieve a 2-tailed 95% power (α=0.05) we recruited a training set of 55 patients, all with pathologically confirmed lung cancer: Stage I (n=13), Stage II (n=7), Stage IIIa (n=10), Stage IIIb (n=18) & Stage IV (n=7). Baseline (BL) blood samples were taken prior to start of therapy. If possible, a second blood sample (T1) was taken after completion of radiotherapy (~60 days), n=46 patients. Blood was filtered by CellSieveTM filtration and CAMLs quantified. Analysis by CAML size of Results: CAMLs were found in 93% of BL samples averaging 3.2 CAMLs/7.5mL. Patients with at least one CAML ≥50 µm had reduced PFS (HR=2.9, 95%CI 1.4-6.0, p=0.010). 46 patients agreed to a follow up blood draw. 13 of the 46 patients had an increase of CAML size to ≥50 µm, but 3 patients had a decrease to Conclusions: Our data suggests that for lung cancer patients undergoing definitive radiation therapy, the presence of enlarged CAMLs appears to predict patients that are resistant to treatment. Furthermore, these circulating stromal cells appear useful for sequential monitoring of patients that may prognosticate who are likely to progress after treatment. Citation Format: Daniel L. Adams, Jianzhong He, Yawei Qiao, Hui Gao, James Reuben, Ignacio I. Wistuba, Cha-Mei Tang, Steven H. Lin. A circulating stromal cell subpopulation that accurately predicts resistance and progression in treatment naïve lung cancer patients receiving definitive radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2915.

3053 Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common in the peripheral blood of cancer patients that are prognostic for progressive disease. Further, it has been shown that changes in CAML size (i.e. enlargement above 50µm) can predict progression free survival (PFS) in thoracic cancers (e.g. lung). We enrolled 104 unresectable non-small cell lung cancer (NSCLC) patients, with an initial training set review of 54 patients, to determine if change in CAML size after radiation therapy was predictive PFS. Methods: A 2 year single blind prospective study was undertaken to test the relationship of ≥50µm CAMLs to PFS based on imaging in lung patients before and after induction of chemo radiation, or radiation therapy. To achieve a 2-tailed 90% power (α = 0.05) we recruited a training set of 54 patients and validation set of 50 patients all with pathologically confirmed unresectable NSCLC: Stage I (n = 14), Stage II (n = 16), Stage III (n = 61) & Stage IV (n = 13). Baseline (BL) blood samples were taken prior to start of therapy & a 2nd blood sample (T1) was taken after completion of radiotherapy (~30 days). Blood was filtered by CellSieve filtration and CAMLs quantified. Analysis by CAML size of < 49 µm or ≥50 µm was used to evaluate PFS hazard ratios (HRs) by censored univariate & multivariate analysis. Results: CAMLs were found in 95% of samples averaging 2.7 CAMLs/7.5mL sample at BL, with CAMLs ≥50 µm having reduced PFS (HR = 2.2, 95%CI1.3-3.8, p = 0.003). At T1, 18 patients had increased CAML size ≥50 µm with PFS (HR = 4.6, 95%CI2.5-8.3, p < 0.001). In total, ≥50 µm CAMLs at BL was 76% accurate at predicting progression within 24 months while ≥50 µm CAMLs at T1 was 83% accurate at predicting progression. Conclusions: In unresectable NSCLC patients, enlargement of CAMLs during treatment is an indicator active progression. We identify that a single ≥50 µm CAML after induction of radiotherapy, in our training set and confirmed in our validation set, is an indicator of poor prognosis. We suggest that changes in CAML size during therapy may indicate the efficacy of therapy and could potentially help shape subsequent therapeutic decisions.

2547 Background: Detection of molecular residual disease via circulating tumor DNA (ctDNA) analysis after chemoradiation (CRT) in localized non-small cell lung cancer (NSCLC) predicts risk of relapse. We explored the hypotheses that (1) patients with undetectable ctDNA after CRT may not require consolidation immunotherapy (CI) and (2) ctDNA analysis could monitor the effectiveness of CI in patients with residual ctDNA after CRT. Methods: We applied CAPP-Seq ctDNA analysis to 88 plasma and matched leukocyte samples collected pre-CRT, post-CRT but pre-CI, and mid-CI in 22 patients with Stage IIB-IIIB NSCLC treated with CRT followed by CI. Identification of patient-specific tumor variants was performed using tumor tissue or pretreatment plasma, and ctDNA was quantified using a tumor mutation-informed bioinformatic strategy. Freedom from progression (FFP) defined radiographically by RECIST 1.1 criteria was compared in patients with ctDNA detected or not detected at pre-CI and mid-CI landmarks. Results: Median follow up from the start of CRT was 11 months. ctDNA detection was associated with inferior rates of FFP when compared to patients with ctDNA not detected both pre-CI (12-month 33% vs. 76%, P = 0.015, HR 7.51, 95% CI 1.47-38.24) and mid-CI (12-month 0% vs. 86%, P < 0.0001, HR 123.3, 95% CI 16.21-937.8). In patients with undetectable ctDNA after CRT, FFP was similar to a historical cohort of patients with undetectable ctDNA after CRT alone (12-month 88% vs. 87%, P = 0.56, HR 0.55, 95% CI 0.07-4.18), suggesting that such patients may not benefit from CI. All patients with detectable ctDNA pre-CI in whom ctDNA increased mid-CI developed progressive disease. Finally, in 2 patients with ctDNA detected after CRT, CI led to elimination of ctDNA at the mid-CI timepoint. One of these patients developed an isolated local recurrence 22 months after CRT and the other patient is currently disease free at 11 months, suggesting clinical benefit from CI. Conclusions: Our results suggest that ctDNA analysis may allow personalization and response monitoring of CI following CRT for NSCLC. Validation in more patients followed by prospective testing in clinical trials will be required to establish clinical utility of such an approach.

Suboptimal cellular DNA repair capacity (DRC) has been shown to be associated with enhanced cancer risk, but genetic variants affecting the DRC phenotype have not been comprehensively investigated. In this study, with the available DRC phenotype data, we analyzed correlations between the DRC phenotype and genotypes detected by the Illumina 317K platform in 1,774 individuals of European ancestry from a Texas lung cancer genome-wide association study. The discovery phase was followed by a replication in an independent set of 1,374 cases and controls of European ancestry. We applied a generalized linear model with single nucleotide polymorphisms as predictors and DRC (a continuous variable) as the outcome. Covariates of age, sex, pack-years of smoking, DRC assay-related variables, and case–control status of the study participants were adjusted in the model. We validated that reduced DRC was associated with an increased risk of lung cancer in both independent datasets. Several suggestive loci that contributed to the DRC phenotype were defined in ERCC2/XPD, PHACTR2, and DUSP1. In summary, we determined that DRC is an independent risk factor for lung cancer, and we defined several genetic loci contributing to DRC phenotype. Cancer Res; 73(1); 256–64. ©2012 AACR.

e21062Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common in the peripheral blood of patients with solid tumors. Further, CAMLs ≥50µ...

Purpose: HSP90 inhibition is well known to sensitize cancer cells to radiation. However, it is currently unknown whether additional radiosensitization could occur in the more clinically relevant setting of chemoradiation (CRT). We used the potent HSP90 inhibitor ganetespib to determine whether it can enhance CRT effects in NSCLC. Experimental Design: We first performed in vitro experiments in various NSCLC cell lines combining radiation with or without ganetespib. Some of these experiments included clonogenic survival assay, DNA damage repair, and cell-cycle analysis, and reverse-phase protein array. We then determined whether chemotherapy affected ganetespib radiosensitization by adding carboplatin–paclitaxel to some of the in vitro and in vivo xenograft experiments. Results: Ganetespib significantly reduced radiation clonogenic survival in a number of lung cancer cell lines, and attenuated DNA damage repair with irradiation. Radiation caused G2–M arrest that was greatly accentuated by ganetespib. Ganetespib with radiation also dose-dependently upregulated p21 and downregulated pRb levels that were not apparent with either drug or radiation alone. However, when carboplatin–paclitaxel was added, ganetespib was only able to radiosensitize some cell lines but not others. This variable in vitro CRT effect was confirmed in vivo using xenograft models. Conclusions: Ganetespib was able to potently sensitize a number of NSCLC cell lines to radiation but has variable effects when added to platinum-based doublet CRT. For optimal clinical translation, our data emphasize the importance of preclinical testing of drugs in the context of clinically relevant therapy combinations. Clin Cancer Res; 22(23); 5876–86. ©2016 AACR.