Differential Responses to Immune Checkpoint Inhibitors are Governed by Diverse Mismatch Repair Gene Alterations

PURPOSE

The response to immune checkpoint inhibitors (ICI) in deficient mismatch repair (dMMR) colorectal cancer and endometrial cancer is variable. Here, we explored the differential response to ICIs according to different mismatch repair alterations.

EXPERIMENTAL DESIGN

Colorectal cancer (N = 13,701) and endometrial cancer (N = 3,315) specimens were tested at Caris Life Sciences. Median overall survival (mOS) was estimated using Kaplan-Meier. The prediction of high-, intermediate-, and low-affinity epitopes by tumor mutation burden (TMB) values was conducted using R-squared (R2).

RESULTS

Compared with mutL (MLH1 and PMS2) co-loss, the mOS was longer in mutS (MSH2 and MSH6) co-loss in all colorectal cancer (54.6 vs. 36 months; P = 0.0.025) and endometrial cancer (81.5 vs. 48.2 months; P < 0.001) patients. In ICI-treated patients, the mOS was longer in mutS co-loss in colorectal cancer [not reached (NR) vs. 36 months; P = 0.011). In endometrial cancer, the mOS was NR vs. 42.2 months; P = 0.711]. The neoantigen load (NAL) in mutS co-loss compared with mutL co-loss was higher in colorectal cancer (high-affinity epitopes: 25.5 vs. 19; q = 0.017, intermediate: 39 vs. 32; q = 0.004, low: 87.5 vs. 73; q < 0.001) and endometrial cancer (high-affinity epitopes: 15 vs. 11; q = 0.002, intermediate: 27.5 vs. 19; q < 0.001, low: 59 vs. 41; q < 0.001), respectively. R2 ranged from 0.25 in mutS co-loss colorectal cancer to 0.95 in mutL co-loss endometrial cancer.

CONCLUSIONS

Patients with mutS co-loss experienced longer mOS in colorectal cancer and endometrial cancer and better response to ICIs in colorectal cancer. Among all explored biomarkers, NAL was higher in mutS co-loss and may be a potential driving factor for the observed better outcomes. TMB did not reliably predict NAL.

Modulatory effects of dietary prickly pear (Opuntia ficus-indica) peel on high salinity tolerance, growth rate, immunity and antioxidant capacity of Nile tilapia (Oreochromis niloticus)

This study evaluated the effects of prickly pear (Opuntia ficus-indica) peel (PPP) on salinity tolerance, growth, feed utilization, digestive enzymes, antioxidant capacity, and immunity of Nile tilapia (Oreochromis niloticus). PPP was incorporated into four iso-nitrogenous (280 g kg-1 protein) and iso-energetic (18.62 MJ kg-1) diets at 0 (PPP0), 1 (PPP1), 2 (PPP2), and 4 (PPP4) g kg-1. Fish (9.69 ± 0.2 g) (mean ± SD) were fed the diets for 75 days. Following the feeding experiment, fish were exposed to a salinity challenge (25‰) for 24 h. Fish survival was not affected by the dietary PPP inclusion either before or after the salinity challenge. Fish fed the PPP-supplemented diets showed lower aspartate aminotransferase, alanine aminotransferase, cortisol, and glucose levels compared to PPP0, with the lowest values being observed in PPP1. Fish fed dietary PPP had higher growth rates and feed utilization than PPP0. Quadratic regression analysis revealed that the best weight gain was obtained at 2.13 g PPP kg-1 diet. The highest activities of protease and lipase enzymes were recorded in PPP1, while the best value of amylase was recorded in PPP2, and all PPP values were higher than PPP0. Similarly, PPP1 showed higher activities of lysozyme, alternative complement, phagocytic cells, respiratory burst, superoxide dismutase, glutathione peroxidase and catalase, and lower activity of malondialdehyde than in PPP0. Further increases in PPP levels above 2 g kg-1 diet led to significant retardation in the immune and antioxidant parameters. Thus, the inclusion of PPP at about 1 to or 2 g kg-1 diet can improve stress tolerance, immunity, and antioxidant capacity in Nile tilapia.

Randomized, phase II selection study of ramucirumab and paclitaxel versus FOLFIRI in refractory small bowel adenocarcinoma: SWOG S1922

TPS784

Background: Small bowel adenocarcinoma is a rare malignancy with limited evidence to support the choice of systemic chemotherapy beyond the frontline setting. Though second-line therapy has historically been extrapolated from colorectal cancers, recent molecular data has demonstrated small bowel adenocarcinoma to be genomically unique when compared to either colon or gastric cancer. Retrospective analyses of irinotecan- and taxane-based therapies and one prospective phase II clinical trial of nab-paclitaxel have demonstrated clinical activity in this cancer. Ramucirumab/paclitaxel represents an active combination in the management of gastric cancer. SWOG 1922 evaluates the use of FOLFIRI or ramucirumab/paclitaxel in the second- and later-line setting for small bowel adenocarcinoma. Methods: This is randomized, phase II, selection design clinical trial of FOLFIRI (5-fluorouracil, leucovorin and irinotecan) every two weeks or ramucirumab D1,15 and paclitaxel D1,8,15 every 4 weeks with the primary endpoint of progression-free survival (PFS). Secondary endpoints include response rate, overall survival, and safety. Archived paraffin tumor tissue collection and serial blood collections are included for correlative analyses. Key eligibility criteria include having mismatch repair proficient/microsatellite stable small bowel adenocarcinoma (ampullary location excluded); metastatic or locally advanced unresectable disease; prior fluoropyrimidine and/or oxaliplatin therapy; no prior treatment with irinotecan, ramucirumab, or taxanes; no recent bleeding, blood clots, or bowel perforation/fistula; and Zubrod performance status of 0/1. Measurable disease is not required. The null hypothesis is median PFS of 2.5 months. If a median PFS of at least 3.5 months is observed in one or both arms, the goal is to choose the better regimen with respect to this endpoint. The design provides a 90% probability of selecting the more active arm, assuming a hazard ratio of 1.4, if both arms meet this threshold. This trial is open and, as of September 1, 2021, 21 of 94 planned patients have been enrolled. NCT04205968 Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819, U10CA180820, U10CA180821, U10CA180868; and in part by Eli Lilly and Company. Clinical trial information: NCT04205968 .

NSABP C-14: CORRECT-MRD II—Second colorectal cancer clinical validation study to predict recurrence using a circulating tumor DNA assay to detect minimal residual disease

TPS284

Background: Detectable ctDNA after resection of early-stage solid tumors has been associated with very high risk of recurrence, suggesting ctDNA is evidence of minimal residual disease (MRD). Several studies are ongoing to investigate the role of ctDNA in the optimal management of pts with colorectal cancer using different assay technologies. Methods: This is a prospective, observational, multicenter study in the United States and Canada of 750 patients who have undergone complete surgical resection for stage II or III colorectal cancer, who have FFPE tissue available from the primary resection sufficient for a novel bespoke MRD assay and are willing to provide serial whole blood specimens for ctDNA analysis. Participants are asked to provide study specimens after definitive surgical resection, pre-recurrence follow-up, and clinical recurrence (if applicable). Recently amended eligibility criteria include inclusion of rectal cancer patients who have completed neo-adjuvant therapy and surgical resection, as well as enrollment of all stage II and III patients regardless of microsatellite stability status. The Oncotype Colon Recurrence Score will be assessed on all patients from their surgical specimen if criteria are met for this testing. ctDNA will be analyzed with an NGS-based tumor-informed MRD assay that identifies somatic genomic alterations from DNA derived from the patient’s tumor tissue, subtracts germline variants, and detects a selected subset of tumor-specific (bespoke) ctDNA in their blood. All primary tumor specimens will undergo full exome and transcriptome sequencing using the Oncomap ExTra assay. If there is evidence of disease recurrence, the metastatic tissue will also undergo Oncomap ExTra testing, which will be shared with participants. The primary objective is to validate the association of post-definitive therapy and pre-recurrence follow-up ctDNA positivity with recurrence-free interval (RFI). Further objectives are to assess the: sensitivity and specificity of ctDNA positivity for subsequent clinical recurrence; contribution of post-surgery baseline, post-adjuvant therapy, and pre-recurrence follow-up ctDNA results on RFI; time from positive ctDNA to clinical recurrence in participants who had a positive ctDNA result; and compare the Oncotype Colon Recurrence Score estimate of 3-year recurrence risk with the observed 3-year recurrence rate. The primary analysis will use a Cox proportional hazards regression applied to the RFI with ctDNA result (positive or negative) measured at post-surgical baseline (or end of adjuvant therapy if used) and serially after that as a single, time-dependent covariate. Protocol#: NSABP C-14 / ES 16-002. Support: NSABP Foundation, ExactSciences Clinical trial information: 05210283 .

Comprehensive characterization of KRAS mutations and inter-relation with primary tumor location in colorectal cancers

231

Background: The recent development of KRAS G12C inhibitors underscores the potential to target KRAS mutations. Right-sided and left-sided colon tumors (RT and LT) exhibit different molecular features. We characterize the prevalence of KRAS-variants, interrelation with primary tumor location, and association with immune biomarkers in CRC. Methods: We retrospectively reviewed CRC tumors of all stages (with known sidedness) that underwent NGS with the Tempus xT assay (DNA-seq of 648 genes at 500x coverage, full transcriptome RNA-seq). Bivariate analyses were performed to compare KRAS alterations, immune biomarkers, and co-mutations by tumor location. P-values comparing individual co-mutations between groups were adjusted for false discovery (FDR). Results: A total of 3,391 CRC were analyzed (RT: n = 442 [13%], transverse: n = 116 [3%], LT; n = 2,833 [84%]) of which 1486 (44%) tumors harbored KRAS mutations. Overall, KRAS mutations were more frequent in RT compared to transverse tumors and LT (52% vs 41% vs 43%, p<0.001, respectively). The most frequent KRAS mutation variants observed were G12D (29 %), G12V (22%), G13D (16%), and G12C (5.7%). There was no significant difference in the prevalence of KRAS variant types between LT and RT (p=0.5). Significant differences in genomic co-mutations with various KRAS variants were observed in the following genes: TP53, FBXW7, and NF1 (FDR- P<0.05). RT and transverse tumors were more likely have MSI-H and TMB-H (>10 mut/mb) status than LT (MSI-H: 18% vs 22% vs 2.2% and TMB-H (20% vs 22% vs 3%, P<0.001), respectively. CRC tumors harboring G13D variants were more likely to be associated with and MSI-H and TMB-H status (and 7.7% and 8.5%) compared to G12D (2.8 % and 3.9 %), G12V (1.8 % and 2.1%), and G12C (0% and 2.4%); P = 0.003 and 0.001. Conclusions: The most frequent KRAS mutation variants observed in CRC tumors were G12D, G12V, G13D, and G12C. There was no significant difference in the prevalence of KRAS variant types between tumors of the left vs right colon. CRC tumors that harbored G13D variants were significantly more likely to be associated with MSI-H and TMB-H status. [Table: see text]

Impact of KRAS mutation variants on clinicopathological features and outcomes in patients with metastatic pancreatic adenocarcinoma

749

Background: Most pancreatic ductal adenocarcinoma (PDAC) exhibit KRAS mutations. A subset of PDACs harbor KRAS wild-type (WT) and appear to carry better prognosis. Given the recent development of KRAS G12C inhibitors, it is imperative to better understand KRAS variants in contemporary cohorts. Herein, we characterized the prevalence of the different KRAS variants and its impact on clinicopathological features and outcomes. Methods: A retrospective review of patients with metastatic PDAC and a known KRAS mutation status who underwent next-generation sequencing (NGS) from liver biopsy was performed. Descriptive statistics analyzed the differences in clinicodemographic features by presence and type or absence of KRAS variants. Kaplan-Meier method was used to assess overall survival (OS). Cox regression was used to study the relationship between KRAS variants and OS when confounding factors were adjusted. Results: 50 pts with PDAC diagnosed at a single community-based institution between 2011-2018 were evaluated. Median age at diagnosis was 68 years (24-80 range), 68% were male, and 76% presented with metastases. Most (86%) tumors harbored KRAS mutations. The most frequent variants were G12V (44%), G12D (37%), G12R (9%), Q61R (5%), G12C (2%), Q61H (2%). Sex (p=0.03) and tumor differentiation (p=0.04) varied according to mutation status and KRAS variant subtype. However, no significant difference was observed in age, race, smoking status, location of primary, and performance status (PS) in KRAS variants. Overall, median OS in months was 8.9 (95% CI 6.7-14.3) for KRAS mutated patients and 11.2 (95% CI 2.1-33.5) for patients with WT. Among patients with KRAS mutations, median OS in months by variant was as following: G12V 9.6 (95%CI 6.6-17.2), G12D 8.4 (95%CI 3.9-15.4), G12R 8.2 (95%CI 1-20.8), and Q61R 11.8 (95%CI 1.3-22.3). However, these differences did not reach statistical significance (p=0.72). In multivariable analyses, female sex (HR 0.16, 95% CI 0.03-0.81, p=0.03) and no receipt of chemotherapy (38.5 95% CI 2.1-698.50, p=0.01) were significant predictors of death. KRAS mutation variant type was not an independent predictor of death. Conclusions: No significant difference was observed in metastatic PDAC with KRAS mutations compared to WT. However, numerical difference in OS were observed among the various KRAS mutation type. Hence, larger studies are needed to better define the effect of KRAS type on outcomes.

Phase II Single-Arm Study of Palbociclib and Cetuximab Rechallenge in Patients with KRAS/NRAS/BRAF Wild-Type Colorectal Cancer

BACKGROUND

Cetuximab is often administered to patients with KRAS wild-type (KRAS-WT) metastatic colorectal cancer (mCRC), although resistance inevitably develops. We hypothesized that co-inhibition of the epidermal growth factor receptor (EGFR) with cetuximab and downstream cyclin-dependent kinases (CDK) 4/6 with palbociclib would be effective for anti-EGFR rechallenge in KRAS-WT mCRC.

METHODS

We designed a single-arm, Simon's 2-stage, phase II trial of cetuximab and palbociclib in KRAS-WT mCRC treated with ≥2 prior lines of therapy. We report here on cohort B rechallenging patients with anti-EGFR-based therapy who had disease control of at least 4 months on prior anti-EGFR therapy. Primary endpoint was disease control rate (DCR) at 4 months.

RESULTS

Ten evaluable patients were enrolled in this cohort. The 4-month DCR was 20%, which did not fulfill the prespecified 4-month DCR rate to continue. Median progression-free survival was 1.8 months and median overall survival was 6.6 months. Three patients had stable disease, although overall response rate was 0%. Most common treatment-related grades 3-4 adverse events were lymphopenia and leukopenia.

CONCLUSION

Selection of patients for anti-EGFR rechallenge using clinical criteria alone was insufficient to identify response to palbociclib + cetuximab. Additional biomarkers are needed to select anti-EGFR rechallenge and circulating tumor DNA (ctDNA) analysis is planned for samples collected in this study. (ClinicalTrials.gov Identifier: NCT03446157).

Multi-omic Characterization of Pancreatic Ductal Adenocarcinoma Relates CXCR4 mRNA Expression Levels to Potential Clinical Targets

PURPOSE

Chemokines are essential for immune cell trafficking and are considered to have a major impact on the composition of the tumor microenvironment. CX-chemokine receptor 4 (CXCR4) is associated with poor differentiation, metastasis, and prognosis in pancreatic ductal adenocarcinoma (PDAC). This study provides a comprehensive molecular portrait of PDAC according to CXCR4 mRNA expression levels.

EXPERIMENTAL DESIGN

The Cancer Genome Atlas database was used to explore molecular and immunologic features associated with CXCR4 mRNA expression in PDAC. A large real-word dataset (n = 3,647) served for validation and further exploratory analyses. Single-cell RNA analyses on a publicly available dataset and in-house multiplex immunofluorescence (mIF) experiments were performed to elaborate cellular localization of CXCR4.

RESULTS

High CXCR4 mRNA expression (CXCR4high) was associated with increased infiltration of regulatory T cells, CD8+ T cells, and macrophages, and upregulation of several immune-related genes, including immune checkpoint transcripts (e.g., TIGIT, CD274, PDCD1). Analysis of the validation cohort confirmed the CXCR4-dependent immunologic TME composition in PDAC irrespective of microsatellite instability-high/mismatch repair-deficient or tumor mutational burden. Single-cell RNA analysis and mIF revealed that CXCR4 was mainly expressed by macrophages and T-cell subsets. Clinical relevance of our finding is supported by an improved survival of CXCR4high PDAC.

CONCLUSIONS

High intratumoral CXCR4 mRNA expression is linked to a T cell- and macrophage-rich PDAC phenotype with high expression of inhibitory immune checkpoints. Thus, our findings might serve as a rationale to investigate CXCR4 as a predictive biomarker in patients with PDAC undergoing immune checkpoint inhibition.

Impact of RAS mutations on immunologic characteristics of the tumor microenvironment (TME) in patients with microsatellite instability-high (MSI-H) or mismatch-repair–deficient (dMMR) colorectal cancer (CRC)

3067

Background: The KEYNOTE-177 trial demonstrated pembrolizumab’s superiority over first-line chemotherapy in patients with MSI-H/dMMR mCRC. However, in a subgroup analysis, patients with KRAS or NRAS mutations did not show the same favorable PFS benefit with PD-1 blockade therapy (HR 1,19; CI 0.68-2,07). The impact of RAS mutations on the immunologic characteristics of the TME of MSI-H/dMMR CRC has not been well characterized. Methods: A retrospective review of deidentified records of patients with MSI-H/dMMR CRC tumors was conducted using next-generation sequencing data (Tempus |xT assay, DNA-seq of 595-648 genes at 500x coverage, and full transcriptome RNA-seq). MSI-H determined by assessment of 239 loci by NGS. Several immune markers were assessed, including tumor mutational burden (TMB), neoantigen tumor burden (NTB, ScanNeo), PD-L1 expression, immune infiltration, and canonical immune pathways (82 geneset signatures). Results: A total of 463 MSI-H/dMMR CRCs were analyzed, of which 110 (24%) tumors harbored RAS mutations ( RASmut) [ KRAS: 93%, NRAS 6% and HRAS 1%}, while 353 were RAS-wild-type ( RASWT). Compared to MSI-H/dMMR RASWT, MSI-H/dMMR RASmut tumors were more frequently identified in males (53% vs. 38%; P= 0.005), and younger patients (median age: 57 yrs vs. 71 yrs, P< 0.001). Although there were no significant differences in median TMB (40 mut/MB for both, p = 0.9) or frequency of TMB-high status (≥10 mut/MB) between the two groups, RASmuttumors tended to have a lower tumor NTB (16 vs. 12 neoAg/Mb, P <0.001) and lower % CD8 T cell but higher % CD4 T cell infiltration (P < 0.05). Significant differences were observed in genomic alterations co-occurring with RASmut compared to RASWT (e.g., MLH1 (23% vs. 8.8%, P < 0.001), MSH6 (36% vs. 24%, P = 0.017), APC (60% vs. 20%, P< 0.001), ARID1A (54% vs 30%, P< 0.001), PIK3CA (36% vs 19%, P< 0.001), and TP53 (32% vs. 19%, P = 0.014). Pathway enrichment analysis identified 14 differentially expressed pathways among RASmut tumors. Four pathways showed significant upregulation, including Hedgehog, Wnt, TGFβ, and cancer stem cell pathways. Ten pathways of interest showed significant downregulation among RASmut tumors. The majority (9/10) were immune-related, including cytokine signaling [ JAK-STAT, TGFβ, TH1], innate immune [ NK cells], and adaptive immune events (CD8 T cell, Tregs)]. Conclusions: MSI-H/dMMR CRCs harboring RASmut exhibited overall upregulated WNT/SHH pathway activity, coupled with reduced NTB, cytokine signaling, and innate and adaptive immune events. TGFβ is pleiotropic, and different members were associated with variable modulation. These data suggest that MSI-H/dMMR CRCs harboring RAS mutations are less immunogenic and appeared to contain a TME that is less sensitive to immune checkpoint blockade than MSI-H/dMMR RAS wt CRCs.

The differential response to immune checkpoint inhibitors in colorectal and endometrial cancer patients according to different mismatch repair alterations

3625

Background: In colorectal cancer (CRC) and endometrial cancer (EC) patients (pts), preliminary data suggest a differential response to immune checkpoint inhibitors (ICIs) according to different MMR alterations. The drivers of this difference remain unknown and no reliable predictive biomarker has been found. We explored the genomic alterations, tumor mutation burden (TMB), immune-related gene expressions and signatures, tumor microenvironment (TME), neoantigen load and median overall survival (mOS) inCRC and EC pts treated with ICIs with different MMR alterations. Methods: 13,701 CRC and 3,315 EC specimens were tested at Caris Life Sciences (Phoenix, AZ) with Next Gen Sequencing (NGS) of DNA (592-gene or whole exome) and RNA (whole transcriptome). MMR/MSI status was determined by IHC of MMR protein and/or NGS. Immune cell abundance was quantified using quanTIseq. Gene expression profiles were analyzed for T cell-inflamed signature (TIS) and IFN-gamma scores. Immune epitope prediction was performed using the NetMHCpan v4.0 method in the Immune Epitope Database. Real-world mOS was obtained from insurance claims data and calculated from tissue collection or ICIs start to last contact. Statistical significance was determined using chi-square/Fisher-Exact and adjusted for multiple comparisons (adjusted p < 0.05). Results: In CRC, 84 (0.6%) pts had intact expression of MLH1 and PMS2 and co-loss of MSH2 and MSH6 (MutS) and 648 (4.7%) had co-loss of MLH1 and PMS2 and intact MSH2 and MSH6 (MutL). 117 (0.9%) had other MMR IHC loss. APC, KRAS, ERBB2, ERBB3 and MSH2 mutations rates were higher in MutS while BRAF mutation rate was higher in MutL. B cell, NK cell content and neoantigen load (high affinity epitopes: p < 0.05, intermediate: p < 0.01, low: p < 0.001) were higher in MutS. The mOS in MutS (N = 149) vs. MutL (N = 980) was 56 months (m) vs. 36 m (p = 0.003). In ICI-treated pts, the mOS in MutS (N = 28) vs. MutL (N = 149) was not reached (NR) vs. 32 m (p = 0.005). BRAF mutation didn’t impact survival in MutL. In EC, 48 (1.4%) pts had MutS and 915 (27.6%) had MutL. 81 (2.4%) had other MMR IHC loss. IHC-PD-L1, TMB, neoantigen load (high affinity epitopes: p < 0.01, intermediate: p < 0.0001, low: p < 0.0001), TIS, IFN-gamma scores, immune related gene expressions, TME (Macrophage M1, CD8+) were higher in MutS. The mOS in MutS (N = 94) vs. MutL (N = 1804) was NR vs. 47 m (p < 0.001). In ICI-treated pts, the mOS in MutS (N = 11) vs. MutL (N = 273) was NR vs. NR (p = 0.559). Conclusions: This is the largest study to explore differential response to ICIs in CRC and EC pts with different MMR alterations. In pts with CRC and EC, the mOS was longer in MutS compared to MutL. In ICI-treated pts, the mOS was longer in MutS compared to MutL in CRC but not in EC. Among the explored biomarkers, neoantigen load was higher in MutS compared to MutL in both CRC and EC and maybe the driving factor for differential response to ICIs.

NSAB C-14: CORRECT-MRD II—Second colorectal cancer clinical validation study to predict recurrence using a circulating tumor DNA assay to detect minimal residual disease

TPS3632

Background: Patients (pts) with stage II and III colon cancer (CC) have unique post-operative decisions regarding adjuvant chemotherapy (ACT). There is a subset of stage II pts with defined clinicopathologic features associated with poor prognosis who may benefit from ACT, although more discriminating and objective predictors of benefit are needed. In addition, there may be a subset of Stage III CC pts who could tolerate a de-escalation of ACT or who may require intensification of ACT to improve clinical outcome. Detectable ctDNA after resection of early-stage solid tumors has been associated with very high risk of recurrence, suggesting ctDNA is evidence of minimal residual disease (MRD). Several studies are ongoing to investigate the role of ctDNA in the optimal management of pts with CC using different assay technologies. Methods: This is a prospective, observational, multicenter study in the United States and Canada of 750 pts who have undergone complete surgical resection for stage II or III CC, have FFPE tissue available from the primary resection sufficient for a novel bespoke MRD assay, and are willing to provide serial whole blood specimens for ctDNA analysis. Subjects are asked to provide study specimens at baseline, pre-recurrence follow-up, and clinical recurrence (if applicable) study visits. ctDNA will be analyzed with an NGS-based MRD assay that identifies somatic genetic alterations from DNA derived from the pt’s tumor tissue, subtracts germline variants, and detects a subset of these tumor-specific (bespoke) ctDNA in the pt’s blood. The primary objective is to validate the association of post-definitive therapy and pre-recurrence follow-up ctDNA positivity with recurrence-free interval (RFI). Further objectives are to assess the: sensitivity and specificity of ctDNA positivity for subsequent clinical recurrence; contribution of post-surgery baseline, post-adjuvant therapy, and pre-recurrence follow-up ctDNA results on RFI; time from positive ctDNA to clinical recurrence in subjects who had a positive ctDNA result; and compare the Oncotype Colon Recurrence Score estimate of 3 yr recurrence risk with the observed 3 yr recurrence rate. The primary analysis will use a Cox proportional hazards regression applied to the RFI with ctDNA result (positive or negative) measured at post-surgical baseline (or end of ACT if ACT was used) and serially after that as a single, time-dependent covariate. Protocol: 16-002/NSABP C-14. Support: NSABP Foundation. Clinical trial information: 05210283.

Comparative analysis of microsatellite instability-high (MSI-H) BRAF V600E-mutated versus MSI-H BRAFwild type colorectal cancers (CRC), including tumor microenvironment (TME), associated genomic alterations, and immunometabolomic biomarkers

3066

Background: The BRAFV600E mutation is associated with the hypermethylator phenotype CIMP, which can also lead to the MSI-H phenotype. BRAFV600E mutation and MSI-H/dMMR status seem to be biologically intertwined; however, the impact of coexisting BRAFV600E mutations on the TME and immunometabolomic features of MSI-H/dMMR CRC tumors is not well characterized. Methods: A retrospective review of deidentified records of patients with MSI-H/dMMR CRC tumors was conducted using next-generation sequencing data (Tempus |xT assay: DNA-seq of 595-648 genes at 500x coverage, and full transcriptome RNA-seq). Several immune markers of tumor immunogenicity in BRAF wild-type ( BRAFwt) vs. V600E-mutated (BRAFV600E) tumors were assessed, including tumor mutational burden (TMB), neoantigen tumor burden (NTB, ScanNeo), PD-L1 expression, immune infiltration, and canonical immuno-metabolomic pathways (82 geneset signatures). Results: A total of 459 MSI-H/dMMR CRC tumors were analyzed, of which 123 (27%) tumors harbored BRAFV600Emutations, and 336 (73%) were BRAFwt. MSI-H/dMMR BRAFV600E tumors were more frequently identified in females (69% vs. 55%; P= 0.01), non-Hispanic or non-Latino (100% vs. 73%; P =0.001), and older patients (median age: 76 yrs vs. 62 yrs; P< 0.001). Compared to BRAFWT, BRAFV600E tumors exhibited significantly higher TMB (Median: 49 mut/MB vs. 36 mut/MB; P < 0.001) and were more frequently associated with TMB-High status (> 10 mut/MB; 100% vs. 95%; P = 0.008); however, no significant differences were observed with tumor NTB, immune score, or T cell infiltration (CD4 or CD8). NK cell infiltration was higher in the BRAFV600Ecohort (< 0.001). When compared to BRAFWT tumors , BRAFV600E tumors harbored a greater frequency of mutations in MSH6(42% vs. 20%), B2M (33% vs. 16%), BRCA2 (31% vs. 12%), ATM (23% vs. 12%), and TP53 (30% vs. 19%) but a lower frequency of MSH2 (3.3% vs. 11%), all P< 0.05. Pathway enrichment analysis identified 10 significantly altered signaling pathways, most of which related to stromal/immune cell signaling and metabolism. Five were upregulated among BRAFV600E tumors: glycerophospholipid, galactose, cyclin-dependent cell signaling; Nucleotide, and TH1 inflammation. Five pathways were downregulated (Wnt, Notch, TH17 inflammation, amino sugar, and cancer stem cell signaling). Conclusions: MSI-H/dMMR BRAFV600E CRCs undergo broad metabolic reprogramming (e.g., glycerophospholipidgalactose, nucleotide). A rise in lipid metabolism, particularly with NK inflammation, suggests that BRAFV600Emutated tumors may be associated with a non-classical immune component. BRAFV600E and BRAFwt CRCs exhibited similar NTB and T cell infiltration, suggesting that both are likely to benefit from immune checkpoint inhibitors.

Phase 3, multicenter, randomized study of CPI-613 with modified FOLFIRINOX (mFFX) versus FOLFIRINOX (FFX) as first-line therapy for patients with metastatic adenocarcinoma of the pancreas (AVENGER500)

4023

Background: Metastatic pancreatic cancer (mPC) remains a deadly disease with very limited treatment options. FFX is a standard first-line therapy for mPC with a median overall survival (mOS) of 11.1 months. CPI-613 is a stable intermediate of a lipoate analog that inhibits pyruvate dehydrogenase and α-ketoglutarate dehydrogenase enzymes of the tricarboxylic cycle preferentially within the mitochondria of cancer cells. In a phase I study, CPI-613+mFFX was safe and exhibited promising signal of efficacy. Methods: A global, randomized phase 3 trial was conducted across 73 sites to investigate the efficacy and safety of CPI-613 in combination with mFFX compared to standard dose FFX in treatment-naïve patients with mPC. Treatment was administered in 2-weekly cycles until progression or intolerable toxicity. In the experimental arm, CPI-613 at 500 mg/m2 was given intravenously on days 1 and 3. The doses of irinotecan, oxaliplatin, and 5-fluorouracil in the experimental arm were 65 mg/m2, 140 mg/m2, and 2,400 mg/2, respectively. Primary endpoint was OS. Secondary endpoints were progression-free survival (PFS), overall response rate (ORR), duration of response, pharmacokinetics, patient reported outcomes and safety. Results: 528 patients were randomly assigned (266 in test and 262 in control arm). There were 362 deaths, with a mOS of 11.1 months for CPI-613+mFFX vs. 11.7 months for FFX [hazard ratio (HR), 0.95; 95% CI, 0.77 to 1.18; P = 0.655]; mPFS was 7.8 months vs. 8.0 months respectively [HR, 0.99; 95% CI, 0.76 to 1.29; P = 0.94]; ORR was 39% in the test arm vs. 34% in the control arm [ORR ratio, 1.23 (95% CI, 0.86 to 1.75)]. Grade ≥ 3 treatment-emergent adverse events with ≥ 10% frequency in CPI-613 plus mFFX vs. FFX arm were diarrhea (11.2% vs. 19.6%), hypokalemia (13.1% vs. 14.9%), anemia (13.9% vs. 13.6%), neutropenia (11.2% vs. 14.0%), thrombocytopenia (11.6% vs. 13.6%) and fatigue (10.8% vs. 11.5%). Conclusions: The addition of CPI-613 to mFFX failed to show significant improvements of ORR, PFS or OS. The mFFX in the test arm that had the lowest prospectively tested doses of FFX was without compromise on PFS or OS and may be considered as a reference for future FFX administration. Clinical trial information: NCT03504423.

Molecular profiling of signet-ring-cell carcinoma (SRCC) from the stomach and colon reveals potential new therapeutic targets

Signet ring cell carcinoma (SRCC) is rare: about 10% of gastric cancer (GC) and 1% of colorectal cancer (CRC). SRCC is associated with poor prognosis, however the underlying molecular characteristics are unknown. SRCCs were analyzed using NGS, immunohistochemistry, and in situ hybridization. Tumor mutational burden (TMB) was calculated based on somatic nonsynonymous missense mutations, and microsatellite instability (MSI) was evaluated by NGS of known MSI loci. A total of 8500 CRC and 1100 GC were screened. Seventy-six SRCC were identified from the CRC cohort (<1%) and 98 from the GC cohort (9%). The most frequently mutated genes in CRC-SRCC were TP53 (47%), ARID1A (26%), APC (25%); in GC-SRCC were TP53 (42%), ARID1A (27%), CDH1 (11%). When compared to non-SRCC histology (N = 3522), CRC-SRCC (N = 37) more frequently had mutations in BRCA1 (11% vs 1%, P < 0.001) and less frequently mutations in APC (19% vs 78%, P < 0.001), KRAS (22% vs 51%, P = 0.001) and TP53 (47% vs 73%, P = 0.001). Among the GC cohort, SRCC (N = 54) had a higher frequency of mutations in CDH1, BAP1, and ERBB2, compared to non-SRCC (N = 540). Our data suggest that SRCCs harbor a similar molecular profile, regardless of the tumor location. Tailored therapy may become available for these patients.

Immune Checkpoint Blockade Therapy in Patients With Colorectal Cancer Harboring Microsatellite Instability/Mismatch Repair Deficiency in 2022

Immune checkpoint inhibitors (ICIs) are shown to be effective among patients with metastatic colorectal cancer (mCRC) harboring high microsatellite instability (MSI-H) and/or mismatch repair deficiency (dMMR), with U.S. Food and Drug Administration approvals for all lines of therapy. In Europe, only pembrolizumab in the first line and the combination of nivolumab and ipilimumab beyond the first line are approved. Many questions remain about the clinical management of MSI-H/dMMR CRC. Biomarkers predictive of immune checkpoint inhibitor resistance among MSI-H/dMMR tumors are needed (1) to select the best treatment for patients with CRC (anti-PD-[L]1 monotherapy alone or combined with anti-CTLA-4 or chemotherapy) and (2) to develop new treatment strategies for patients whose disease progressed after immune checkpoint inhibitor monotherapy. The development of immune checkpoint inhibitors in the adjuvant and neoadjuvant settings is also of great interest for patients harboring MSI-H/dMMR, especially as a substantial proportion have Lynch syndrome or are at high risk of developing cancers in their lifetime and sporadic MSI-H/dMMR cancers occur most frequently in elderly and frail patients. Thus, CRC is not one, but two different diseases: (1) MSI-H/dMMR CRC (seen in 5% of mCRC and 15% of non-mCRC), which is genetically unstable with a high mutational load and many neoantigens, and for which immune checkpoint inhibitors radically changed clinical management, and (2) microsatellite stable CRC with chromosomal instability, for which immune checkpoint inhibitors are not proven efficient.

Landscape of KRASG12C, Associated Genomic Alterations, and Interrelation With Immuno-Oncology Biomarkers in KRAS-Mutated Cancers

Promising single-agent activity from sotorasib and adagrasib in KRAS^G12C-mutant tumors has provided clinical evidence of effective KRAS signaling inhibition. However, comprehensive analysis of KRAS-variant prevalence, genomic alterations, and the relationship between KRAS and immuno-oncology biomarkers is lacking.

Predictors of early mortality in early and late onset pancreatic cancer (PC)

543

Background: The incidence of early-onset PC (EOPC) is rising and is associated with substantial mortality. We sought to identify independent predictors of early mortality in a cohort of EOPC and matched older patients (pts). Methods: Pts with EOPC (≤50 years) and matched cohorts of average (51-69, AOPC) and late (≥70, LOPC) onset PC by sex, race, year of diagnosis, and presence of metastatic disease were identified using the institutional tumor registry for years 2011-2018. Demographic and clinicopathologic characteristics were retrieved. Overall time of survival was assessed using Kaplan-Meier curves and the Cox Proportional Hazards modeling. Multivariable regression was conducted to evaluate for predictors of early mortality in non-metastatic and metastatic pts, defined as either death within six months of diagnosis compared to those surviving at least 12 months. Results: In total, 100 pts with EOPC (median age 47, range 29-50), 100 pts with AOPC (median age 60, range 51-69), and 100 pts with LOPC (median age 78, range 70-93) were analyzed. Of these, 46% were female, 28% were black, and 43% had metastatic disease at presentation. In non-metastatic pts, the 12-mo. survival rate by age group was: EOPC 74.4% (95% CI 59-85), AOPC 60% (95% CI 43-73), and LOPC 32.4% (95% CI 18-47). Variables associated with mortality within 6 months of diagnosis in non-metastatic pts on univariable analysis included age group, BMI ≤25, ECOG performance status (PS), neutrophil-to-lymphocyte ratio ≥5 (NLR5), CA 19-9 ≥130, no surgical resection, and no adjuvant chemotherapy. Multivariable regression confirmed no surgical resection (Odds Ratio [OR] 9.6, 95% CI 3-29), no receipt of chemotherapy (OR 6.9, 95% CI 2-21), and NLR5 (OR 5.4, 95% CI 1-22) as independent predictors for early mortality in non-metastatic pts. In metastatic pts, the 12-mo. survival rate by age group was: EOPC 32.6% (95% CI 19-47), AOPC 27% (95% CI 15-41), and LOPC 5.8% (95% CI 1-16). On univariable analysis, variables associated with mortality within 6 months of diagnosis included age group, ECOG PS, and NLR5. Multivariable regression confirmed LOPC (OR 11.6, 95% CI 2-61) and NLR5 (OR 11, 95% CI 2-54) as independent variables for early mortality. Race, sex, BMI, CA 19-9, smoking, alcohol use, primary tumor location, and site of metastases were not associated with early mortality in metastatic pts. No difference in independent predictors of early mortality between EOPC and older pts were identified. Conclusions: In this cohort of EOPC and matched older pts, LOPC (age ≥70) and NLR5 were independently associated with early mortality by 6 months in metastatic pts. In non-metastatic pts, lack of curative intent surgery, no receipt of chemotherapy, and NLR5 were independently associated with early mortality. There were no independent predictors for early mortality that distinguished EOPC and older pts. Further work is needed to identify prognostic factors unique to EOPC.

The prevalence of common KRAS variants and associated outcomes in patients with metastatic colorectal cancer (mCRC)

173

Background: KRAS is the most common driver oncogene in mCRC. Comprehensive analysis of KRAS variants prevalence and the relationship between variants and outcomes are lacking. Herein, we aimed to examine the impact of KRAS variants on outcomes in patients (pts) with mCRC. Methods: A retrospective review of pts with mCRC with known KRAS mutation status was performed. Fisher’s exact test was used to analyze the association between KRAS variants. Cox Proportional Hazard modeling was used to study the relationship between KRAS variants and overall survival (OS). Kaplan-Meier method was used to assess OS. Results: A total of 423 pts diagnosed with mCRC from 2014-2020 with available extended KRAS status were evaluated. Median age at diagnosis was 59.8 yrs (22.3-92 range), 57% were male, 22% were Black, and 75% presented with de novo metastatic disease. A majority (56%) of tumors harbored KRAS mutations. The most frequent KRAS variants were G12D 47% (111), G12V 12% (28), G12C 13% (31), G13D 9% (21), and 20% (47) were other variants. In univariate analyses, the presence of a KRAS mutation, Black race, de novo metastatic disease, age, receipt of chemotherapy, and receipt of surgery were associated with OS. Tumor location was not associated with OS. In multivariable analyses, mutation type was a significant predictor of death and the presence of G12D was associated with an increased risk of death compared to G12V and KRAS wildtype. There was no increased risk of death in pairwise comparisons of G12D and G13D or other KRAS variants. Black race, de novo metastatic disease, and no receipt of surgery were additional independent predictors of death (Table). With a median follow-up of 25.7 months (mo.), median OS was 35.5 mo. (95% CI 10.5-50.9) with G12C, Not Reached (NR) (95% CI 21-NR) with G12V, 36.2 mo. (95%CI 14.9-58.5) with G13D, 26.2 mo. (95% CI 21.8-37) with G12D, 39.6 mo. (95% CI 22.4-47.9) for other KRAS mutations, and 59.6 mo. (95%CI 48.2-NA) for KRAS wildtype, respectively (p=0.0003). Conclusions: Our findings highlight differences in unadjusted overall survival when comparing G12D to some other KRAS variants. Codon and amino acid-specific mutations of KRAS should be considered when evaluating prognosis and further study on treatment effects and sequencing is warranted. [Table: see text]

Phase II single-arm study of palbociclib and cetuximab rechallenge in KRAS/NRAS/BRAF wild-type (KRAS WT) metastatic colorectal cancer (mCRC) patients (pts)

88

Background: Cetuximab is a monoclonal antibody (mAb) targeting the epidermal growth factor receptor (EGFR) and is given alone or in combination with chemotherapy in the 60% of mCRC that are KRAS WT. Unfortunately, resistance inevitably develops, which may be related to downstream upregulation of the extracellular-signal-regulated kinase (ERK) pathway. Rechallenge with anti-EGFR mAb may be effective in patients previously benefiting from anti-EGFR therapy, but median progression-free survival is < 4 months, indicating need for novel more effective combinations for rechallenge. Co-inhibition of EGFR and downstream cyclin-dependent kinases 4/6 (CDK4/6) may overcome ERK pathway reactivation. We hypothesized that the addition of the CDK4/6 inhibitor palbociclib to cetuximab would be effective for anti-EGFR rechallenge in KRAS-WT mCRC. Methods: LCCC1717 was a multicenter, single-arm, Simon’s two stage phase II study of cetuximab and palbociclib in KRAS WT mCRC treated with ≥2 prior regimens (NCT03446157). Eligible pts were enrolled to one of two cohorts depending on previous anti-EGFR mAb therapy; we report here on cohort B, which enrolled pts who had disease control for at least 4 months with anti-EGFR therapy. Cohort B was designed to initially enroll 10 evaluable pts; if ≥ 4 pts had disease control at least 4 months, then 11 more pts would be enrolled. Treatment included cetuximab 400 mg/m2 followed by 250 mg/m2 weekly, plus palbociclib 125 mg daily on days 1-21 of a 28-day cycle until progression, toxicity, or withdrawal. Primary endpoint was disease control rate (DCR) at 4 months by RECIST 1.1. Secondary endpoints were overall response rate (ORR), progression free survival (PFS), and overall survival (OS). Results: In cohort B, 10 evaluable pts were enrolled from 2/2018-8/2020 (1 additional pt withdrew after an infusion reaction with first dose of cetuximab). Median age 59, 70% male, 90% left-sided primary. The 4-mo DCR was 2/10 (20%; 95% CI 5-52%). Given this, enrollment in this cohort was halted after first stage. Median PFS was 1.8 mo (95% CI: 1.7, NE) and median OS was 6.6 mo (95% CI: 3.6, NE). No pts had a complete or partial response; 3 pts (30%) had stable disease (SD), including 1 patient with SD for 24.7 months. The regimen was well tolerated; most common treatment-related grade 3-4 adverse events were lymphopenia (27%) and leukopenia (18%). While 55% of pts had acneiform rash, none were grade 3-4. Conclusions: Selection of patients for anti-EGFR rechallenge using clinical criteria alone was insufficient to identify pts likely to respond to palbociclib + cetuximab rechallenge. This emphasizes the need for screening using circulating tumor (ct) DNA of known resistance mutations to select pts for anti-EGFR rechallenge approaches. Translational work assessing ctDNA in this study is planned. Cohort A with anti-EGFR naïve patients continues enrollment. Clinical trial information: NCT03446157.

Impact of preoperative chemoradiotherapy (CRT) on the rectal tumor microenvironment (TME) and associated patient outcomes

157

Background: Pembrolizumab did not improve neoadjuvant rectal score when added to neoadjuvant CRT in the NRG-GI002 study. The impact of CRT on TME in patients (pts) with rectal cancer (RC) has not been well characterized. Methods: We performed a paired analysis on RC tissue taken pre- and post-CRT from pts undergoing long course CRT with a fluoropyrimidine followed by surgery. Samples underwent next-generation sequencing (NGS) and whole transcriptome RNAseq. Ingenuity Pathway Analysis (IPA), Molecular Signature Database (MSigDB), and xCell algorithm were used to dissect TME changes pre/post-CRT. Results: Specimens from 61 pts with MSS-RC were identified: median age, 61y, 75% white, 18% black, and 57% male. Tumor samples from 57 pts underwent NGS: 43 pre-CRT, 48 post-CRT, and 34 paired. A total of 2,642 differentially expressed genes (DEGs) were identified between pre/post CRT tumors and then grouped into 3 main gene sets (GS): “higher eukaryotes transcription factor (E2F) target”, “G2/M cell cycle checkpoint”, and “Immune/Stress”. The 3 GS are mutually exclusive, indicating different cellular processes in response to CRT. E2F and G2/M gene signatures were specifically enriched pre-CRT (p < 0.0001), indicating that treatment alters cell survival, proliferation, and tumor growth. Cell death and apoptosis (p < 0.0001) and the Immune/Stress set, including stromal stress response (p = 0.0004), tissue repair (p = 0.0025), and leukocyte production (p < 0.008), were significantly enriched post-CRT. The xCell algorithm used to assess alteration stromal vs immune response by CRT; Stromal scores increased by 0.100 ± 0.016-fold, while Immune scores increased by 0.047 ± 0.017 (P = 0.015), suggesting a rise in Immune/Stress GS is driven mainly by stromal stress response. The 5 most common gene types upregulated post-CRT were smooth muscle cells, fibroblasts, interstitial dendritic cells, pericytes, and hepatic stellate cells. However, immune alterations trended downward (NK, Th1, and gamma delta T cells) or rose heterogeneously, e.g., a rise in intra-tumoral CD8 T cell subsets (effector, effector memory, or central memory) occurred for 8/35 pts. Fifteen pts (42%) relapsed and/or died after surgery. While CD8 T cell infiltration tends to be associated with better prognosis, it was not statistically significant (p = 0.2277; HR 2.709). CD8 T cell infiltrates were associated with higher prevalence of immune checkpoint transcripts LAG3 (p = < 0.0001) and to a lesser extend PD1 (p = 0.0186) in the tumor, indicating an anergic state of CD8 T cell infiltrates post-CRT. Conclusions: TME of RC tumors mainly identified stress/ wound healing response to CRT. Immune response was heterogeneous among pts; a subset showed a significant rise in CD8 T cell infiltration, indicating an anergic state mainly driven by LAG3. The potential of this pt subset to respond to anti-LAG3 immunotherapy is worthy of further study.

Randomized phase II selection study of ramucirumab and paclitaxel versus FOLFIRI in refractory small bowel adenocarcinoma: SWOG S1922

TPS643

Background: Small bowel adenocarcinoma is a rare malignancy with limited data to support the choice of systemic chemotherapy beyond the frontline setting. Though second-line therapy has historically been extrapolated from colorectal cancers, recent molecular data has demonstrated small bowel adenocarcinoma to be genomically unique when compared to either colon or gastric cancer. Retrospective analyses of irinotecan- and taxane-based therapies and one prospective phase II clinical trial of nab-paclitaxel have demonstrated likely activity in this cancer. SWOG 1922 explores the clinical activity of FOLFIRI and ramucirumab with paclitaxel in the second- and later-line setting for small bowel adenocarcinoma. Methods: This is a randomized phase II selection design clinical trial of FOLFIRI (5-fluorouracil, leucovorin and irinotecan) every two weeks or ramucirumab D1,15 and paclitaxel D1,8,15 every 4 weeks with the primary endpoint of progression-free survival (PFS). Secondary endpoints include response rate, overall survival, and safety. Archived paraffin tumor tissue collection and serial blood collections are included for correlative analyses. Key eligibility include having mismatch repair proficient/microsatellite stable small bowel adenocarcinoma (ampullary location excluded); metastatic or locally advanced unresectable disease; prior fluoropyrimidine and/or oxaliplatin therapy; no prior treatment with irinotecan, ramucirumab, or taxanes; no recent bleeding, blood clots, or bowel perforation/fistula; and Zubrod performance status of 0/1. Measurable disease is not required. The null hypothesis is median PFS of 2.5 months. If a median PFS of at least 3.5 months is observed in one or both arms, the goal is to choose the better regimen with respect to this endpoint. The design provides a 90% probably of selecting the more active arm, assuming a hazard ratio of 1.4, if both arms meet this threshold. This trial is open and, as of September 1, 2021, 17 of 94 planned patients have been enrolled. NCT04205968. Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819, U10CA180820, U10CA180821, U10CA180868; and in part by Eli Lilly and Company. Clinical trial information: NCT04205968.

Genomic landscape of ERBB2/3 alterations in colorectal cancer: Comutations, immuno-oncology biomarkers, and consensus molecular subtype

176

Background: ERBB2 is a rapidly emerging therapeutic target for a subset of colorectal cancer (CRC) harboring oncogenic alterations in this gene. Oncogenic ERBB3 mutations have been reported in various cancers including CRC, but little is known about its functional impact. Optimal targeting of this pathway requires understanding of the genomic context in which somatic ERBB2/3 alterations ( ERBB2/3-alt) occur in a real-world CRC population. Methods: We analyzed 7,688 de-identified records from CRC patients that underwent next generation sequencing with the Tempus|xT assay (DNA-seq of 648 genes at 500x coverage, full transcriptome RNA-seq). We assessed the prevalence and association of ERBB2/3-alt with demographics, co-occurring alterations, immuno-oncology biomarkers (microsatellite instability [MSI], tumor mutational burden [TMB], PD-L1 expression), and consensus molecular subtype (CMS, available for the subgroup with primary biopsies and RNA data [n = 2,686]). Results: Overall, 5% (376/7688) of tumors harbored an ERBB2 or ERBB3-alt. 1.9% (n = 143) ERBB2-amplified, 1.3% (n = 97) ERBB2-mutated, 0.9% (n = 72) ERBB3-mutated, < 1% other combinations (excluded from analyses). There were no significant differences in baseline demographics (e.g., age of onset, race and gender) between groups. Patients with ERBB2/3-alt were more likely to be MSI-high and TMB-high (Table). There was a trend towards higher prevalence of positive PD-L1 in ERBB3-alt vs ERBB3-WT tumors. We observed significant differences in co-occurring alterations among ERBB2/3-alt and WT groups (Table). CMS classification did not identify significant differences by ERBB2-alt or ERBB3-alt; ERBB2-alt compared to WT (CMS1: 8.6% vs 13%; CMS2: 24% vs 26%; CMS3: 20% vs 17%; CMS4: 30% vs 34%; p = 0.12) and ERBB3-alt compared to WT (CMS1: 24% vs 13%; CMS2: 12% vs 26%; CMS3: 16% vs 17%; CMS4: 40% vs 34%; p = 0.3). Conclusions: ERBB2/3 mutated CRC are more frequently MSI-H, TMB-high and KRAS mutated than ERBB2/3-WT tumors. Correlation of ERBB2/3 alterations with other genomic alterations including BRAF, TP53, CDK12, PIK3CA, and TOP2A will help advance the clinical development of HER2-targeted therapies.[Table: see text]

Molecular characterization of squamous cell carcinoma of the anal canal

Background

Squamous cell carcinoma of the anal canal (SCCA) is an uncommon malignancy with limited therapeutic options. Nivolumab and pembrolizumab show promising results in patients with SCCA. Human papillomavirus (HPV)-negative tumors are frequently TP53-mutated (TP53-MT) and often resistant to therapy.

Methods

We present a large molecularly-profiled cohort of SCCA, exploring the underlying biology of SCCA, differences between TP53-wild type (TP53-WT) and TP53-MT tumors, and differences between local and metastatic tumors. SCCA specimens (n=311) underwent multiplatform testing with immunohistochemistry (IHC), in situ hybridization (ISH) and next-generation sequencing (NGS). Tumor mutational burden (TMB) was calculated using only somatic nonsynonymous missense mutations. Chi-square testing was used for comparative analyses.

Results

The most frequently mutated genes included PIK3CA (28.1%), KMT2D (19.5%), FBXW7 (12%), TP53 (12%) and PTEN (10.8%). The expression of PD-1 was seen in 68.8% and PD-L1 in 40.5% of tumors. High TMB was present in 6.7% of specimens. HER2 IHC was positive in 0.9%, amplification by chromogenic in situ hybridization (CISH) was seen 1.3%, and mutations in ERBB2 were present in 1.8% of tumors. The latter mutation has not been previously described in SCCA. When compared with TP53-WT tumors, TP53-MT tumors had higher rates of CDKN2A, EWSR1, JAK1, FGFR1 and BRAF mutations. PD-1 and PD-L1 expression were similar, and high TMB did not correlate with PD-1 (P=0.50) or PD-L1 (P=0.52) expression.

Conclusions

Molecular profiling differences between TP53-MT and TP53-WT SCCA indicate different carcinogenic pathways which may influence response to therapy. Low frequency mutations in several druggable genes may provide therapeutic opportunities for patients with SCCA.

Molecular differences between lymph nodes and distant metastases compared with primaries in colorectal cancer patients

Lymph nodes (LNs) and distant metastases can arise from independent subclones of the primary tumor. Herein, we characterized the molecular landscape and the differences between LNs, distant metastases and primary colorectal cancers (CRCs). Samples were analyzed using next generation sequencing (NGS, MiSeq on 47 genes, NextSeq on 592 genes) and immunohistochemistry. Tumor mutational burden (TMB) was calculated based on somatic nonsynonymous missense mutations, and microsatellite instability (MSI) was evaluated by NGS of known MSI loci. In total, 11,871 samples were examined, comprising primaries (N = 5862), distant (N = 5605) and LNs metastases (N = 404). The most frequently mutated genes in LNs were TP53 (72%), APC (61%), KRAS (39%), ARID1A (20%), PIK3CA (12%). LNs showed a higher mean TMB (13 mut/MB) vs distant metastases (9 mut/MB, p < 0.0001). TMB-high (≥17mut/MB) and MSI-H (8.8% and 6.9% vs 3.7%, p < 0.001 and p = 0.017, respectively) classifications were more frequent in primaries and LNs vs distant metastases (9.5% and 8.8% vs 4.2%, p < 0.001 and p = 0.001, respectively). TMB-high is significantly more common in LNs vs distant metastases and primaries (P < 0.0001), regardless MSI-H status. Overall, LNs showed significantly different rates of mutations in APC, KRAS, PI3KCA, KDM6A, and BRIP1 (p < 0.01) vs primaries, while presenting a distinct molecular profile compared to distant metastases. Our cohort of 30 paired samples confirmed the molecular heterogeneity between primaries, LNs, and distant metastases. Our data support the hypothesis that lymphatic and distant metastases harbor different mutational landscape. Our findings are hypothesis generating and need to be examined in prospective studies.

Reevaluating Disease-Free Survival as an Endpoint vs Overall Survival in Stage III Adjuvant Colon Cancer Trials

BACKGROUND

Disease-free survival (DFS) with a 3-year median follow-up (3-year DFS) was validated as a surrogate for overall survival (OS) with a 5-year median follow-up (5-year OS) in adjuvant chemotherapy colon cancer (CC) trials. Recent data show further improvements in OS and survival after recurrence in patients who received adjuvant FOLFOX. Hence, reevaluation of the association between DFS and OS and determination of the optimal follow-up duration of OS to aid its utility in future adjuvant trials are needed.

METHODS

Individual patient data from 9 randomized studies conducted between 1998 and 2009 were included; 3 trials tested biologics. Trial-level surrogacy examining the correlation of treatment effect estimates of 3-year DFS with 5 to 6.5-year OS was evaluated using both linear regression (RWLS2) and Copula bivariate (RCopula2) models and reported with 95% confidence intervals (CIs). For R2, a value closer to 1 indicates a stronger correlation.

RESULTS

Data from a total of 18 396 patients were analyzed (median age = 59 years; 54.0% male), with 54.1% having low-risk tumors (T1-3 and N1), 31.6% KRAS mutated, 12.3% BRAF mutated, and 12.4% microsatellite instability high or deficient mismatch repair tumors. Trial-level correlation between 3-year DFS and 5-year OS remained strong (RWLS2 = 0.82, 95% CI = 0.67 to 0.98; RCopula2 = 0.92, 95% CI = 0.83 to 1.00) and increased as the median follow-up of OS extended. Analyses limited to trials that tested biologics showed consistent results.

CONCLUSIONS

Three-year DFS remains a validated surrogate endpoint for 5-year OS in adjuvant CC trials. The correlation was likely strengthened with 6 years of follow-up for OS.

Impact of Sociodemographic Disparities and Insurance Status on Survival of Patients with Early-Onset Colorectal Cancer

Background

Low socioeconomic status (SES) has been linked to worse survival in patients with colorectal cancer (CRC); however, the impact of SES on early‐onset CRC remains undescribed.

Materials and Methods

Retrospective analysis of data from the National Cancer Database (NCDB) between 2004 and 2016 was conducted. We combined income and education to form a composite measure of SES. Logistic regression and χ² testing were used to examine early‐onset CRC according to SES group. Survival rates and Cox proportional hazards models compared stage‐specific overall survival (OS) between the SES groups.

Results

In total, 30,903 patients with early‐onset CRC were identified, of whom 78.7% were White; 14.5% were Black. Low SES compared with high SES patients were more likely to be Black (26.3% vs. 6.1%) or Hispanic (25.3% vs. 10.5%), have T4 tumors (21.3% vs. 17.8%) and/or N2 disease (13% vs. 11.1%), and present with stage IV disease (32.8% vs. 27.7%) at diagnosis (p < .0001, all comparisons). OS gradually improved with increasing SES at all disease stages (p < .001). In stage IV, the 5‐year survival rate was 13.9% vs. 21.7% for patients with low compared with high SES. In multivariable analysis, SES (low vs. high group; adjusted hazard ratio [HR_adj], 1.35; 95% confidence interval [CI], 1.26–1.46) was found to have a significant effect on survival (p < .0001) when all of the confounding variables were adjusted. Insurance (not private vs. private; HR_adj, 1.38; 95% CI, 1.31–1.44) mediates 31% of the SES effect on survival.

Conclusion

Patients with early‐onset CRC with low SES had the worst outcomes. Our data suggest that SES should be considered when implementing programs to improve the early detection and treatment of patients with early‐onset CRC.

Implications for Practice

Low socioeconomic status (SES) has been linked to worse survival in patients with colorectal cancer (CRC); however, the impact of SES on early‐onset CRC remains undescribed. In this retrospective study of 30,903 patients with early‐onset CRC in the National Cancer Database, a steady increase in the yearly rate of stage IV diagnosis at presentation was observed. The risk of death increased as socioeconomic status decreased. Race and insurance status were independent predictors for survival. Implementation of programs to improve access to care and early diagnostic strategies among younger adults, especially those with low SES, is warranted.

The incidence of and mortality from early‐onset colorectal cancer (CRC) is on the rise. This article details the relationship between socioeconomic status and clinical outcomes of young adults with early‐onset CRC.

Molecular profile of BRCA-mutated biliary tract cancers

Introduction

Prognosis of biliary tract cancers (BTC) remains dismal and novel treatment strategies are needed to improve survival. BRCA mutations are known to occur in BTC but their frequency and the molecular landscape in which they are observed in distinct sites of BTC remain unknown.

Material and methods

Tumour samples from 1292 patients with BTC, comprising intrahepatic cholangiocarcinoma (IHC, n=746), extrahepatic cholangiocarcinoma (EHC, n=189) and gallbladder cancer (GBC, n=353), were analysed using next-generation sequencing (NGS). Tumour mutational burden (TMB) was calculated based on somatic non-synonymous missense mutations. Determination of tumour mismatch repair (MMR) or microsatellite instability (MSI) status was done by fragment analysis, immunohistochemistry and the evaluation of known microsatellite loci by NGS. Programmed death ligand 1 expression was analysed using immunohistochemistry.

Results

Overall, BRCA mutations were detected in 3.6% (n=46) of samples (BRCA1: 0.6%, BRCA2: 3%) with no significant difference in frequency observed based on tumour site. In GBC and IHC, BRCA2 mutations (4.0% and 2.7%) were more frequent than BRCA1 (0.3% and 0.4%, p<0.05) while in EHC, similar frequency was observed (2.6% for BRCA2 vs 2.1% for BRCA1). BRCA mutations were associated with a higher rate in subjects with MSI-H/deficient mismatch repair (19.5% vs 1.7%, p<0.0001) and tumours with higher TMB, regardless of the MMR or MSI status (p<0.05).

Conclusions

BRCA mutations are found in a subgroup of patients with BTC and are characterised by a distinct molecular profile. These data provide a rationale testing poly(ADP-ribose)polymeraseinhibitors and other targeted therapies in patients with BRCA-mutant BTC.

Increased neutrophil infiltration and lower prevalence of tumor mutation burden and microsatellite instability are hallmarks of RAS mutant colorectal cancers

3563

Background: The tumor microenvironment (TME) of colorectal cancers (CRC) is modulated by oncogenic drivers such as KRAS. The TME comprises a broad landscape of immune infiltration. How tumor genomics associates with the immune cell landscape is less known. We aim to characterize immune cell types in RAS wild-type (WT) and mutant (MT) CRC, and to examine the prevalence of immuno-oncologic (IO) biomarkers (e.g. tumor mutation burden (TMB), PD-L1, MSI-H/dMMR) in these tumors. We performed genomic and transcriptomic analysis to confirm associations of mutant RAS with immune infiltration of the TME conducive to metastasis vs. potential response to immunotherapies. Methods: A total of 7,801 CRC were analyzed using next-generation sequencing on DNA (NextSeq, 592 Genes and WES, NovaSEQ), RNA (NovaSeq, whole transcriptome equencing) and IHC (Caris Life Sciences, Phoenix, AZ). MSI/MMR was tested by FA, IHC and NGS. TMB-H was based on a cut-off of > 10 mutations per MB). Immune cell fraction was calculated by QuantiSeq (Finotello 2019, Genome Medicine). Significance was determined by X2 and Fisher-Exact and p adjusted for multiple comparisons (q) was <0.05. Results: Mutant KRAS was seen in 48% of mCRC tumors; NRAS in 3.7%, HRAS in 0.1%. The distribution was similar in patients < or >= than 50 yrs. In MSS tumors, there was a significantly higher neutrophil infiltration in KRAS MT (median cell fraction 6.6% vs. 5.9%) and NRAS MT (6.9%) overall and also when individual codons were studied. B cells, M2 macrophages, CD8+ T cells, dendritic cells and fibroblasts were lower in KRAS mutant tumors; B cells and M1 macrophages are lower in NRAS (q<0.05). dMMR/MSI-H was significantly more prevalent in RAS WT (9.1%) than in KRAS (2.9%) or NRAS MT (1.8%) tumors, and highest in HRAS MT tumors (60%, q<0.05).TMB-H was more prevalent in RAS WT (11%) than KRAS (5.8%) or NRAS (5.1%) MT, and highest in HRAS MT tumors (70%, all q<0.05). In MSS tumors, KRAS MT tumors showed more TMB-H than WT (3.1% vs. 2.1%, q<0.05), especially in KRAS non 12/13/61 mutations (5.5%, vs. 2.1%, q<0.05) and G12C (4.4%, p<0.05). PD-L1 expression was studied: in MSS tumors, KRAS-G12D (10.4%) and G13 MT (11.8%) showed higher mutation rates than RAS WT tumors (q<0.05). Conclusions: KRAS & NRAS mutations are associated with increased neutrophil abundance, with codon specific differences, while HRAS shows no difference. Overall CD8+ T cells and B cells are less abundant in KRAS & NRAS mutants; substantial variability was seen amongst different protein changes. RAS mutations were more prevalent overall than generally reported, but did not vary by age. These results demonstrate significant differences in the TME of RAS mutant CRC that identify variable susceptibilities to immuno-oncologic agents, and provide further detailed characterization of heterogeneity between RAS variants, at the molecular as well as immunogenic levels.

High CXCR4 expression in pancreatic ductal adenocarcinoma as characterized by an inflammatory tumor phenotype with potential implications for an immunotherapeutic approach

4021

Background: Immunotherapy is considered ineffective in the majority of patients with pancreatic ductal adenocarcinoma (PDAC), a consequence of a highly immunosuppressive tumor microenvironment (TME). However, treatment induced inhibition of CXC chemokine receptor 4 (CXCR4) and programmed cell death protein-1 (PD-1) in the COMBAT trial caused T cell infiltration and tumor regression in a subset of PDAC patients. Elucidating a phenotype that predicts response is clinically relevant. We performed a comprehensive molecular landscape study in PDAC evaluating CXCR4 RNA expression. Methods: 3,647 PDAC specimens were centrally analysed. NextGen DNA sequencing (NextSeq, 592 gene panel or NovaSeq, whole-exome sequencing), whole-transcriptome RNA sequencing (NovaSeq) and immunohistochemistry (Caris Life Sciences, Phoenix, AZ) were performed. Gene expression is reported as TPM (Transcripts per million). Pathway gene enrichment analyses were done using GSEA (Subramaniam 2015, PNAS). Immune cell fraction was calculated by QuantiSeq (Finotello 2019, Genome Medicine). The cohort was stratified in quartiles according to CXCR4 RNA expression status. Results: Overall, CXCR4 expression was higher in primary tumors compared to distant metastasis (38 vs. 28 TPM, p < 0.0001). CXCR4-high (top quartile: > 59 TPMs), when compared to CXCR4-low (bottom quartile: < 17 TPM) PDACs, were characterized by a high prevalence of mutations in signal transduction pathway genes (e.g. GNAS: 3.6 vs. 0.5%), an increased infiltration of immune cells (e.g. CD8+ T cells, M1 macrophages), and a higher expression of HLA-DRA and HLA-E (all p < 0.0001). We detected an upregulation of CXCL9, CXCL10, CXCL12, CCL5, IDO1 and LAG3 in CXCR4-high compared to CXCR4-low tumors. In contrast, lower PD-L1 expression (17.4 vs. 13.1%, p = 0.02), genomic loss of heterozygosity (17.4 vs. 10.8%), and a lower frequency of gene amplifications in ERBB2 (2.1 vs. 0.1%), TNFRSF14 (2.0 vs. 0.1%), and TP53 (82 vs. 73%, all p < 0.0001) were observed. Moreover, CXCR4-high expression was associated with a better survival (HR: 1.417, 95% CI [1.168-1.72], p < 0.001). Conclusions: This is the first study comprehensively investigating the molecular landscape of PDACs according to CXCR4 RNA expression. High CXCR4 expression is associated with an improved survival and a pro-inflammatory phenotype that may identify a subset of tumors with greater responsiveness to immunotherapeutic approaches.

A randomized phase III study of immune checkpoint inhibition with chemotherapy in treatment-naive metastatic anal cancer patients: A trial of the ECOG-ACRIN cancer research group (EA2176)

TPS3614

Background: Anal cancer is growing in annual incidence globally and human papillomavirus (HPV) remains the predominant risk factor underlying its development. Due to its relative rarity, clinical trials in anal cancer have historically been difficult to conduct and treatment options for metastatic disease remain limited. Carboplatin/paclitaxel (CP) was compared to cisplatin/5-fluorouracil (historical standard of care) in a recent randomized phase II clinical trial (InterAACT; EA2133) in treatment-naïve metastatic anal cancer, finding that response rates were equivocal, but that overall survival (OS) was significantly longer in the CP arm (20 months vs 12.3 months, p = 0.014). Additionally, reduced grade 3/4 toxicities were seen in the CP arm. NCI9673, a single-arm phase II study, established safety and efficacy of nivolumab in previously-treated metastatic anal cancer. Progression-free survival (PFS) was 4.1 months (95% CI 3.0-7.9) and OS was 11.5 months (95% CI 7.1-not estimable). Multiple randomized trials in lung cancer have demonstrated efficacy of platinum-based chemotherapy combined with checkpoint inhibitors. Together these studies form the rationale behind combining CP and nivolumab in treatment-naïve metastatic anal cancer. Methods: EA2176 (NCT04444921) is the first NCTN phase III randomized clinical trial in treatment-naïve metastatic anal cancer. Stratification factors include HIV status and history of chemoradiation for curative intent. Patients will be randomized to carboplatin (AUC = 5, Day 1) plus paclitaxel (80mg/m2, Days 1, 8, 15) +/- nivolumab 240mg IV (Cycle 1 = Days 1, 15; Cycle ≥2 = Day 1, 480mg) q 28-days until disease progression or treatment intolerance. CP will be given for up to 6 cycles, while nivolumab will be continued as maintenance for up to 2 years. The primary endpoint is PFS. Secondary objectives include OS, response rate, and toxicity. Goal enrollment is 205 patients and the study continues accrual. This sample size will provide 80% power at a two-sided α of 0.05 to detect a 4.8-month improvement in PFS assuming 8 months in the control arm. Novel correlative studies include sequential quantitative tumor-derived cell-free HPV ctDNA levels (serotypes 16 and 18; Sysmex-Inostics SafeSEQ NGS assay). Correlative funding provided in part by the Farrah Fawcett Foundation and Sysmex Inostics, Inc. Clinical trial information: NCT04444921.

Landscape of KRASG12C, associated genomic alterations, and interrelation with immuno-oncology (IO) biomarkers

3127

Background: Sotorasib has shown promising activity in cancer patients (pts) specifically harboring the KRASG12C mutation. Response rates vary significantly by tumor type, suggesting KRASG12C pathogenesis may be cancer-type-dependent. Methods: We retrospectively analyzed de-identified records of 79,004 pts with various cancer types that underwent Tempus xT and xF next generation sequencing assays. Fisher’s exact test was used to analyze the association between cancer subtypes and KRAS variants. Logistic regression was used to study co-mutations between KRASG12C and other oncogenes, as well as the association between KRAS variants and IO biomarkers. False discovery rate-adjusted P-value (FDR P) was used for multiple testing. Results: In total, 13,578 (17.4%) tumors harbored KRAS mutations, of which 1,632 were G12C; 750 KRAS wild-type (WT) tumors gained KRAS mutation on follow-up testing, with 79 harboring G12C. The most frequent KRAS variants across all cancers were G12D, G12V, G12C, and G13D (see Table). The distribution of KRAS variants significantly varied by cancer type, with G12C and G12D being the most prevalent in non-small cell lung (NSCLC) and colorectal (CRC) cancers, respectively. G12C was most prevalent in NSCLC (9%), appendiceal cancer (3.9%), CRC (3.2%), tumors of unknown origin (1.6%), and pancreatic cancer (1.3%). Compared to non-G12C, G12C was more frequently identified in females (56% vs. 51%, FDR P = 0.0005), smokers/prior smokers (85% vs. 56%, FDR P < 0.0001), and pts > 60 years of age (73% vs. 63%, FDR P = 0.0006). While no G12C tumors exhibited BRAFV600E co-mutations, BRAFnon-V600E co-mutations were seen in 3.1% of pts. Significant differences were observed in genomic alterations co-occurring with G12C compared to non-G12C (e.g., STK11 (20.6% vs 6%), KEAP1 (15.4% vs 4.6%), SMAD4 (7.2% vs 19%), and PDGFRA (5.8% vs 3%); FDR P < 0.0001). However, G12C and oncogene co-mutations were not significantly different between NSCLC and CRC, except for KEAP1 (FDR_ P = 0.04). Compared to non-G12C and WT, G12C tumors were associated with TMB-High and PD-L1 over expression but were less likely to have MSI-H status (FDR P < 0.0001; Table). Conclusions: Our data suggest that KRAS variants significantly differ by cancer type. Tumors harboring KRASG12C were significantly associated with high TMB and PD-L1 overexpression. KRASG12C mutation appeared to be associated with smoking status. These results may guide future therapeutic strategies.[Table: see text]

A comprehensive landscape of BRCA1 versus BRCA2 associated molecular alterations and survival outcome across 35 cancer types

3120

Background: Poly (ADP-ribose) polymerase inhibitors (PARPi) are effective therapies for some patients with both germline and somatic BRCA1/2 mutations (MTs) or with homologous recombination repair deficiency (HRD). We aimed to characterize molecular differences between BRCA1 and BRCA2 MTs and their prognostic and/or predictive impact on PARPi outcomes in various cancer subtypes using real world data (RWD). Methods: Tumor samples obtained from patients with 35 types of cancer were analyzed by whole exome sequencing (WES, Novaseq) at Caris Life Sciences (Phoenix, AZ). High genomic loss of heterozygosity (gLOH-H) was defined as LOH-H in ≥16% of tested loci. MSI/MMR was tested by fragment analysis, IHC, and WES. Overall survival (OS) extracted from insurance claims was calculated from start of treatment or tissue collection until last contact or death using Kaplan-Meier curves. P-values adjusted for multiple comparisons (q-value of < 0.05 was considered to be significant). Results: In total, 17,640 tumors were included, of which 776 (4.3%) had tumor-based BRCA1/2 MTs. BRCA1/2 MTs were most commonly seen in ovarian (N = 221/2187, 10.1%), breast (138/2506, 5.5%), prostate (61/1131, 5.4%), pancreatic (48/1430, 3.4%), and non-small cell lung (100/4046, 2.5%) cancers. BRCA2 MTs were more frequent than BRCA1 except in ovarian cancers. BRCA1 MTs were more common in younger pts (median age, 61 vs 65 years, p <.001). When compared to BRCA2 MTs, BRCA1 MTs were more often associated with gLOH-H (64% vs 51%, p <.001) and TP53 MT (80% vs 53%, p <.001) in all tumor types. In NSCLC, EGFR mutations were exclusively seen in BRCA2 compared to BRCA1 (10.3 vs. 0%, P = 0.038). The EGFR mutations that co-occurred with BRCA2 mutations were L858R (N = 1), Exon19del (N = 4), and L861Q (N = 1). KRAS was more frequently mutated in BRCA1-mutated NSCLC ( BRCA1: 32% vs. BRCA2: 16%, p =.056). In univariate analyses, overall BRCA1/2 MTs were associated with improved OS compared to wild type (HR 1.38, 95% CI [1.31-1.45], P <.0001). This effect was seen in ovarian (1.42 [1.29-1.57], p < 0.0001) and triple-negative breast cancers (TNBC) (1.18, [1.09-1.28], p <.001); but was not observed in prostate, pancreatic, or non-TNBC breast cancer subtypes. In all breast cancers, BRCA2 MTs had a superior OS (0.68, [0.51-0.89], p =.005) compared to BRCA1, while no differences were seen in other cancers. Using RWD, PARPi treated-patients with BRCA2 MTs had worse OS than BRCA1 MTs (HR 1.4, [1.09-1.80], p = 0.009); but this was not significant when individual cancers were considered. Conclusions: BRCA1 and BRCA2 MTs had variable power to be prognostic and predictive for PARPi efficacy among different cancer types using RWD. About 2.5% of NSCLCs harbor BRCA1/2 MT. Additional genomic exploration may refine biomarkers predictive of response to PARPi and may highlight features within the tumor microenvironment of importance in the setting of HRD.

Colorectal Cancer: In the Pursuit of Health Equity

Colorectal cancer mortality has decreased considerably following the adoption of national screening programs, yet, within at-risk subgroups, there continue to be measurable differences in clinical outcomes from variations in screening, receipt of chemotherapy, radiation or surgery, access to clinical trials, research participation, and survivorship. These disparities are well-described and some have worsened over time. Disparities identified have included race and ethnicity, age (specifically young adults), socioeconomic status, insurance access, geography, and environmental exposures. In the context of the COVID-19 pandemic, colorectal cancer care has necessarily shifted dramatically, with broad, immediate uptake of telemedicine, transition to oral medications when feasible, and considerations for sequence of treatment. However, it has additionally marginalized patients with colorectal cancer with historically disparate cancer-specific outcomes; among them, uninsured, low-income, immigrant, and ethnic-minority patients-all of whom are more likely to become infected, be hospitalized, and die of either COVID-19 or colorectal cancer. Herein, we outline measurable disparities, review implemented solutions, and define strategies toward ensuring that all have a fair and just opportunity to be as healthy as possible.

Impact of socioeconomic status (SES) on colorectal cancer patient survival: An analysis of 890,867 patients in the National Cancer Database (NCDB)

19

Background: SES has been associated with outcomes in cancer patients (pts). We examined associations between SES and survival of pts with colorectal cancers (CRC). Methods: The NCDB was used to examine the association of SES status with clinicopathological features and outcomes of colorectal cancer pts, categorized by the income and education level of their area of residence. Logistic regression, Cox proportional hazard model, and chi-square test were used to examine the differences between groups. Results: A retrospective analysis of 890,867 pts with CRC (right-sided 34.1%, transverse 11.9%, left-sided 46.2%, and rectal 7.8%) diagnosed between 2004 and 2016, was conducted. About half the pts were male (51.4%); 84.3% were white, 11.2% black, and 4.5% of other races. Overall, 30.8% of pts lived in the highest and 18.4% in the lowest income areas. Twenty-three percent lived in areas comprising the highest high school graduation rate areas (>93%), while 17.4% lived in the lowest (< 79%). Compared to pts living in high-income areas, pts living in the lowest income areas were more likely to be black (OR 6.2, 6.1-6.3), present at a younger age (18-30 yrs vs. >70 yrs; OR 1.28, 1.18-1.39), have T3/T4 disease at presentation (OR 1.03, 95%CI 1.02-1.04), left-sided tumors (OR 1.05, 1.04-1.06), higher Charlson-Deyo score (OR 1.34, 1.33-1.36), and have Medicaid (OR: 3.9, 3.8-4.0) or no health insurance (OR: 2.9, 2.8-3.0). Tumor location and grade, stage, age, sex, race, ethnicity, income, education, insurance status, Charlson-Deyo score, and type of treatment center were independent predictors for survival in the multivariate analysis. Pts living in the lowest income and lowest education areas had a 13% and 4% higher risk of death, respectively, compared to pts in the highest income areas and education areas. Black pts had a 7% increased risk of death. Pts with Medicaid and no insurance coverage had a 44% and 29% increased risk of death, respectively, compared to pts with private insurance. Conclusions: CRC pts living in areas of low income and low education had worse survival. Insurance status and type of treatment center also have a strong impact on survival. Sociodemographic characteristics need to be taken into account and studied further, with the aim of improving outcomes for all pts. [Table: see text]

Chemoradiation-induced molecular alterations and associated outcomes in patients with rectal cancer

104

Background: Molecular changes and associated acquired resistance of rectal tumors following chemoradiotherapy (CRT) have not been well studied. We aimed to examine CRT-induced molecular changes and prognostic associations in rectal cancer patients (pts) undergoing preoperative CRT followed by surgery. Methods: A paired analysis using pre-CRT biopsies and the corresponding post-CRT resected tissues of rectal cancer patients undergoing preoperative CRT followed by surgery was performed. Pre- and post-CRT tumor samples underwent next-generation sequencing (NGS) by Tempus xT assay, which detects a panel of 596 gene mutations, including single nucleotide variants, insertions/deletions, copy number amplifications, and gene rearrangements. The cancer driver gene was detected based on positional clustering of gained mutations using OncodriveCLUST. The paired t-test was used to examine differences in tumor mutational burden (TMB) and microsatellite instability (MSI) between pre- and post-CRT samples. Results: In total, 61pts of median age 61yrs—75% white, 18% black, and 57% male—with localized rectal cancer were studied. NGS testing was performed in 57 pt tumor samples; 43 pts had pre-CRT samples, 48 pts had post-CRT samples, and 34 pts had paired samples. The most frequent genetic alterations seen in the 43 pre-CRT tumor samples were APC (37.2%), ARID1B (30.2%), KMT2C (30.2%), ZFXH3 (25.6%), FLT4 (20.9%), MLLT3 (20.9%), and TP53 (20.9%), whereas in the 48 post-CRT tumor samples, the most frequent mutations were APC (54.2%), TP53 (35.4%), KRAS (27.1%), MKI67 (25.0%), KMT2C (18.8%), APOB (14.6%), and CEBPA (12.5%). Comparing the pre- and post-CRT samples, no significant differences in TMB (median: 5.0 mut/MB vs. 3.3 mut/MB, p=0.922) or MSI status by NGS (p=0.069) were observed. Among the 34 pts with paired samples, 26.5% (9/34) relapsed, and 17.6% (6/34) died. When examining tumor mutation changes between pre- and post-CRT samples (table), the most common gained mutations were seen in APC (29.4% ), MKI67 (26.5% ), KTM2C (17.6%), and TP53 (17.67%); and most common losses were in ARID1B (26.5%), ZFHX3 (26.5%), FLT4 (21.0%) and GATA6 (21.0%). Of the gained mutations, OncodriveCLUST analysis showed that MKI67 potentially carries a driver mutation (pG866V) at exon 12 (p = 0.045), which exclusively existed in the two relapsed pts. Conclusions: Our data suggest that CRT did not alter MSI status nor the level of TMB. However, CRT did result in gained molecular alterations that could be responsible for treatment resistance and predict relapse. Gained MKI67 mutation may be a prognostic biomarker for relapse after CRT. Further prospective studies are needed to validate these findings. [Table: see text]

Socioeconomic status (SES) and survival outcomes in patients with gastrointestinal (GI) cancers: An analysis of 1.4 million patients in the National Cancer Database (NCDB)

458

Background: SES and access to care are factors that may impact patient outcomes. We examined the impact of SES on survival in patients (pts) with GI cancers. Methods: Data obtained from the NCDB were used to examine the association between SES and outcomes of GI cancer pts. Pts were categorized by income and education levels. Logistic regression, Cox proportional hazards models, and chi-square tests were used to examine the differences between the groups. Results: A total of 1,409,177 pts diagnosed with GI cancers between 2004 and 2016 were retrospectively studied (table). The majority of pts were male (54.3%), and 83.7% were white, 11.5% black, and 4.7% of other races. Of the entire cohort, 31% of pts lived in the highest income areas, whereas 18.3% were in the lowest and 50.6% in middle-income areas; 23% lived in the highest high school graduation rate (>93%) areas, whereas 17.4% lived in the lowest graduation rate (< 79%) areas; and 82.4% resided in metropolitan areas. Pts in the lowest compared to highest income areas were more likely to be black (OR: 6.5, 6.4-6.6), uninsured (2.9, 2.8-3.0), or have Medicaid (4.13, 4.04-4.22), and have a Charlson-Deyo score ≥ 1 (1.35, 1.33-1.36). In the multivariate analysis, cancer type, stage, tumor differentiation, income, education, insurance status, gender, race, Charlson-Deyo score, and type of treatment center were independent predictors for survival. After controlling for other factors, black pts had a 3% increased risk of death (HRadj = 1.03; 1.02-1.03; p < 0.001). Pts from lowest vs highest education areas had a 2% increased risk of death (HRadj = 1.02; 1.01-1.03; p < 0.001). Pts from the lowest income vs highest income areas had a 13% increased risk of death (HRadj = 1.13; 1.12-1.14; p < 0.001). Pts with Medicaid insurance had a 33% (HRadj: 1.33, CI 1.32-1.34, p < 0.001) and uninsured pts had 22% (HRadj: 1.22 (1.20-1.23, p < 0.001) increased risk of death compared to pts with private insurance. Pts from urban or rural areas vs metropolitan areas had a 1% increased risk of death (HRadj = 1.01; 1.00-1.02; p < 0.001). Conclusions: Low SES is associated with worse survival in pts with any GI cancer. Pts with low-income status and Medicaid or no health insurance had the highest risk of mortality. These stark inequities must be addressed with renewed efforts to identify, treat, and better support pts at highest risk for poor outcomes. [Table: see text]

Clinical Validation of a Machine-learning-derived Signature Predictive of Outcomes from First-line Oxaliplatin-based Chemotherapy in Advanced Colorectal Cancer

PURPOSE

FOLFOX, FOLFIRI, or FOLFOXIRI chemotherapy with bevacizumab is considered standard first-line treatment option for patients with metastatic colorectal cancer (mCRC). We developed and validated a molecular signature predictive of efficacy of oxaliplatin-based chemotherapy combined with bevacizumab in patients with mCRC.

EXPERIMENTAL DESIGN

A machine-learning approach was applied and tested on clinical and next-generation sequencing data from a real-world evidence (RWE) dataset and samples from the prospective TRIBE2 study resulting in identification of a molecular signature, FOLFOXai. Algorithm training considered time-to-next treatment (TTNT). Validation studies used TTNT, progression-free survival, and overall survival (OS) as the primary endpoints.

RESULTS

A 67-gene signature was cross-validated in a training cohort (N = 105) which demonstrated the ability of FOLFOXai to distinguish FOLFOX-treated patients with mCRC with increased benefit from those with decreased benefit. The signature was predictive of TTNT and OS in an independent RWE dataset of 412 patients who had received FOLFOX/bevacizumab in first line and inversely predictive of survival in RWE data from 55 patients who had received first-line FOLFIRI. Blinded analysis of TRIBE2 samples confirmed that FOLFOXai was predictive of OS in both oxaliplatin-containing arms (FOLFOX HR, 0.629; P = 0.04 and FOLFOXIRI HR, 0.483; P = 0.02). FOLFOXai was also predictive of treatment benefit from oxaliplatin-containing regimens in advanced esophageal/gastro-esophageal junction cancers, as well as pancreatic ductal adenocarcinoma.

CONCLUSIONS

Application of FOLFOXai could lead to improvements of treatment outcomes for patients with mCRC and other cancers because patients predicted to have less benefit from oxaliplatin-containing regimens might benefit from alternative regimens.

Early-onset pancreatic cancer: an institutional series evaluating end-of-life care

PURPOSE

Little is known about the use of palliative and hospice care and their impact on healthcare utilization near the end of life (EOL) in early-onset pancreatic cancer (EOPC).

METHODS

Patients with EOPC (≤ 50 years) were identified using the institutional tumor registry for years 2011-2018, and demographic, clinical, and rates of referral to palliative and hospice services were obtained retrospectively. Predictors of healthcare utilization, defined as use of ≥ 1 emergency department (ED) visit or hospitalization within 30 days of death, place of death (non-hospital vs. hospital), and time from last chemotherapy administration prior to death, were assessed using descriptive, univariable, and multivariable analyses including chi-square and logistic regression models.

RESULTS

A total of 112 patients with EOPC with a median age of 46 years (range, 29-50) were studied. Forty-four percent were female, 28% were Black, and 45% had metastatic disease. Fifty-seven percent received palliative care at a median of 7.8 weeks (range 0-265) following diagnosis. The median time between last chemotherapy and death was 7.9 weeks (range 0-102). Seventy-four percent used hospice services prior to death for a median of 15 days (range 0-241). Rate of healthcare utilization at the EOL was 74% in the overall population. Black race and late use of chemotherapy were independently associated with increase in ED visits/hospitalization and hospital place of death.

CONCLUSIONS

Although we observed early referrals to palliative care among patients with newly diagnosed EOPC, short duration of hospice enrollment and rates of healthcare utilization prior to death were substantial.

Redefining Colorectal Cancer by Tumor Biology

Colorectal cancer treatment has undergone a paradigm shift. We no longer see this disease as a singular, anatomic tumor type but rather a set of disease subgroups. Largely because of a better understanding of cancer biology and the introduction and integration of molecular biomarkers-the premise of precision therapy-we are beginning to direct treatments toward the right tumor target(s) in the right patients. The field of molecular profiling is continually evolving, and new biomarkers are constantly being discovered that have investigational, therapeutic, and/or prognostic implications-negative or positive. To date, only a few biomarkers have sufficient actionable, clinical implication to earn international guideline-recommended routine testing. Hence, it is vital that the treating oncologist should know which biomarkers to assess, when in the treatment course to test for them, and how the test is to be done. Correct interpretation of profiling results is imperative. Herein, we focus on international guideline-recommended mutation testing for patients prior to their colorectal cancer treatment initiation. The clinical applications of circulating tumor DNA (ctDNA) in patients with metastatic disease, based on our current knowledge and capabilities, are also addressed.

Comprehensive Genomic Profiling of Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs)

PURPOSE

GEP-NENs are rare malignancies with increasing incidence. Their molecular characteristics are still undefined. We explored the underlying biology of GEP-NENs and the differences between gastrointestinal (GI) and pancreatic (PNEN), high-grade (HG), and low-grade (LG) tumors.

EXPERIMENTAL DESIGN

GEP-NENs were analyzed using next-generation sequencing (NGS; MiSeq on 47 genes, NextSeq on 592 genes), IHC, and in situ hybridization. Tumor mutational burden (TMB) was calculated on the basis of somatic nonsynonymous missense mutations, and microsatellite instability (MSI) was evaluated by NGS of known MSI loci.

RESULTS

In total, 724 GEP-NENs were examined: GI (N = 469), PNEN (N = 255), HG (N = 135), and LG (N = 335). Forty-nine percent were female, and median age was 59. Among LG tumors, the most frequently mutated genes were ATRX (13%), ARID1A (10%), and MEN1 (10%). HG tumors showed TP53 (51%), KRAS (30%), APC (27%), and ARID1A (23%). Immune-related biomarkers yielded a lower prevalence in LG tumors compared with HG [MSI-H 0% vs. 4% (P = 0.04), PD-L1 overexpression 1% vs. 6% (P = 0.03), TMB-high 1% vs. 7% (P = 0.05)]. Compared with LG, HG NENs showed a higher mutation rate in BRAF (5.4% vs. 0%, P < 0.0001), KRAS (29.4% vs. 2.6%, P < 0.0001), and PI3KCA (7% vs. 0.3%, P < 0.0001). When compared with GI, PNEN carried higher frequency of MEN1 (25.9% vs. 0.0%, P < 0.0001), FOXO3 (8.6% vs. 0.8%, P = 0.005), ATRX (20.6% vs. 2.0%, P = 0.007), and TSC2 (6.3% vs. 0.0%, P = 0.007), but lower frequency of mutations in APC (1.0% vs. 13.8%, P < 0.0001).

CONCLUSIONS

Significant molecular differences were observed in GEP-NENs by tumor location and grade, indicating differences in carcinogenic pathways and biology.

Relationship between MLH1, PMS2, MSH2 and MSH6 gene-specific alterations and tumor mutational burden in 1057 microsatellite instability-high solid tumors

Microsatellite instability-high (MSI-H) and tumor mutational burden (TMB) are predictive biomarkers for immune-checkpoint inhibitors (ICIs). Still, the relationship between the underlying cause(s) of MSI and TMB in tumors remains poorly defined. We investigated associations of TMB to mismatch repair (MMR) protein expression patterns by immunohistochemistry (IHC) and MMR mutations in a diverse sample of tumors. Hypothesized differences were identified by the protein/gene affected/mutated and the tumor histology/primary site. Overall, 1057 MSI-H tumors were identified from the 32 932 tested. MSI was examined by NGS using 7000+ target microsatellite loci. TMB was calculated using only nonsynonymous missense mutations sequenced with a 592-gene panel; a subset of MSI-H tumors also had MMR IHC performed. Analyses examined TMB by MMR protein heterodimer impacted (loss of MLH1/PMS2 vs. MSH2/MSH6 expression) and gene-specific mutations. The sample was 54.6% female; mean age was 63.5 years. Among IHC tested tumors, loss of co-expression of MLH1/PMS2 was more common (n = 544/705, 77.2%) than loss of MSH2/MSH6 (n = 81/705, 11.5%; P < .0001), and was associated with lower mean TMB (MLH1/PMS2: 25.03 mut/Mb vs MSH2/MSH6 46.83 mut/Mb; P < .0001). TMB also varied by tumor histology: colorectal cancers demonstrating MLH1/PMS2 loss had higher TMBs (33.14 mut/Mb) than endometrial cancers (20.60 mut/Mb) and other tumors (25.59 mut/Mb; P < .0001). MMR gene mutations were detected in 42.0% of tumors; among these, MSH6 mutations were most common (25.7%). MSH6 mutation patterns showed variability by tumor histology and TMB. TMB varies by underlying cause(s) of MSI and tumor histology; this heterogeneity may contribute to differences in response to ICI.

WRN-Mutated Colorectal Cancer Is Characterized by a Distinct Genetic Phenotype

Werner syndrome gene (WRN) contributes to DNA repair. In cancer, WRN mutations (WRN-mut) lead to genomic instability. Thus, WRN is a promising target in cancers with microsatellite instability (MSI). We assessed this study to investigate the molecular profile of WRN-mut in colorectal cancer (CRC). Tumor samples were analyzed using next-generation sequencing (NGS) in-situ hybridization and immunohistochemistry. Tumor mutational burden (TMB) was calculated based on somatic nonsynonymous missense mutations. Determination of tumor mismatch repair (MMR) or microsatellite instability (MSI) status was conducted by fragment analysis. WRN-mut were detected in 80 of 6854 samples (1.2%). WRN-mut were more prevalent in right-sided compared to left-sided CRC (2.5% vs. 0.7%, p < 0.0001). TMB, PD-L1 and MSI-H/dMMR were significantly higher in WRN-mut than in WRN wild-type (WRN-wt). WRN-mut were associated with a higher TMB in the MSI-H/dMMR and in the MSS (microsatellite stable) subgroups. Several genetic differences between WRN-mut and WRN-wt CRC were observed, i.e., TP53 (47% vs. 71%), KRAS (34% vs. 49%) and APC (56% vs. 73%). This is the largest molecular profiling study investigating the genetic landscape of WRN-mut CRCs so far. A high prevalence of MSI-H/dMMR, higher TMB and PD-L1 in WRN-mut tumors were observed. Our data might serve as an additional selection tool for trials testing immune checkpoint antibodies in WRN-mut CRC.

The landscape of MAP3K1/MAP2K4 alterations in gastrointestinal (GI) malignancies

4113

Background: Inactivating alterations in MAP3K1/MAP2K4 occur in various solid tumors, sensitize cancer models to MEK inhibitors, and have co-mutation partners which may enable therapeutic targeting. Methods: We retrospectively reviewed 20290 GI malignancy patients (pts), comprised of 9986 colorectal carcinoma (CRC) and 10304 non-CRC, whose tumors were profiled with Caris Life Sciences from 2015-2019. Profiling included immunohistochemistry (IHC) with programmed death ligand-1 (PD-L1), next-generation sequencing (NGS), tumor mutational burden (TMB) and deficient mismatch repair or microsatellite instability-high status (dMMR/MSI-H). Results: MAP3K1/MAP2K4-alteration ( MAP3K1/MAP2K4-MT) was more frequent in CRC than non-CRC pts (2.0% v. 1.2%, p<0.0001), with truncating mutations representing the majority of lesions along both genes. While MAP3K1/MAP2K4-MT CRC pts were similar in age and gender to wild-type (WT), mutated non-CRC pts were older (median age 69 v. 65 years) and more likely female (51% v. 42%) compared to WT (both p<0.05). MAP3K1/MAP2K4-MT CRC (25% v. 7%) and non-CRC (30% v. 3%) were more frequently dMMR/MSI-H than WT pts (both p<0.0001). MAP3K1/MAP2K4-MT CRC cases were affiliated with higher TMB and similar rate of PD-L1 expression compared to WT. A higher rate of MAP3K1/MAP2K4-MT CRC pts were right-sided (36% v. 22%, p<0.0001) and transverse (8% v. 4%, p<0.05) compared to WT, whereas a higher frequency of WT cases were left-sided (20% v. 28%, p<0.05) and rectal (15% v 23%, p<0.05). Of microsatellite stable (MSS) CRC pts, those with MAP3K1/MAP2K4-MT were more likely PIK3CA (26% v. 17%) and APC (85% v. 78%) and less-likely TP53 (64% v. 77%) co-mutated versus WT MSS pts (all p<0.05); no difference was seen in BRAF V600E, ERBB2/ ERBB3 or KRAS co-mutation rate in MSS pts. In both all-comers and MSS CRC, MAP3K1/MAP2K4-MT pts were more frequently co-mutated than WT with ARID1A, POLE, ATM, BRCA2 and PIK3R1 (all ≥7% of MAP3K1/MAP2K4-MT pts, p<0.0001). A higher frequency of all-comer non-CRC GI malignancy pts with MAP3K1/MAP2K4-MT were co-mutated with PIK3CA (13% v. 6%), ERBB2/ERBB3 (8% v. 3%) or APC (13% v. 5%) compared to WT (all p<0.01). For MSS non-CRC GI cases, ARID1A (50% v. 30%) and SMAD4 (21% v. 12%) were more frequently co-mutated in MAP3K1/MAP2K4-MT versus WT pts (all p<0.05). Conclusions: Truncating MAP3K1/MAP2K4 alterations occur in nearly 2% of GI malignancy pts and are more commonly associated with dMMR/MSI-H than WT. Potentially targetable co-mutation partners implicated in MAPK and PI3K pathways as well as POLE, BRCA2 and ATM warrant further evaluation.

Characterization of sociodemographic and clinicopathological features and associated outcomes of patients (Pts) with anal squamous cell cancer (ASCC): Analysis of 44,084 pts in the National Cancer Database (NCDB)

4052

Background: ASCC incidence is rising. There are limited data on the relationships between sociodemographic & clinicopathological features and outcomes of ASCC pts. Methods: Pts diagnosed with ASCC between 2004 and 2016 were retrospectively reviewed. Data obtained from the NCDB were used to examine the impact of sociodemographic status on clinicopathological features and outcomes. Pts were categorized based on low (median < $38,000) or high (≥$68,000) income and low ( > 21% with no high school diploma) or high ( < 7% with no high school diploma) education areas based on zip code at time of diagnosis. Logistic regression and chi-square were used to examine differences between groups. Results: In total, 44,084 pts with ASCC were identified: median age, 59 yrs, 86% white; 11% black; 64% female. Most pts (84%) resided in metro areas; 29.7% vs 19.8% lived in high vs low income areas; 22.9% vs 17.8% lived in high vs low education areas. Seven percent were uninsured, 50% had government (Gov), and 43% had private insurance. Male gender (HR 1.62, CI 1.41-1.85, p < 0.001), low income area (HR 1.28, CI 1.19-1.37, p = 0.014), and insurance status (Gov, HR 1.55, CI 1.32-1.82, p < 0.001 and uninsured, HR 1.37, CI 1.37-1.85, p = 0.039) were associated with a higher risk of death. After adjusting for age, sex, race, stage, grade, insurance status, and comorbidity, pts from low income/education (n = 6695) vs high income/education (n = 4316) areas had a 33 % increased risk of death (HR: 1.33, p < 0.001). Pts with stage IV ASCC in the low income/education (n = 227) vs high income/education (n = 295) groups had worse overall survival (mOS, 1.4 vs 1.9 yrs, p < 0.020). Of the 44,084 pts, 5461 (12.4%) had confirmed HPV status. Of these, 2658 (48.7%) were HPV+ (high risk subtypes) and 2803 (51.3%) were HPV-. Compared to the HPV- pts, HPV+ pts were more likely to be women (71.8% vs 67.8%, p = 0.001), have stage 3 (38.1% vs 33.6%) or 4 (7.9% vs 5.9%, p < 0.001) cancer, and have poorly differentiated (29.5% vs 25.6%, p < 0.001) tumors. There were no significant differences in race, education, income, metro area, insurance status, or comorbidity between the HPV+ and HPV- pts. Moreover, HPV status did not impact OS (HR 0.92, CI 0.81-1.04, p = 0.195). Conclusions: HPV status was not correlated to income, education or insurance status, and did not impact OS in ASCC pts. Male gender and insurance status were associated with increased risk of death. Pts living in low income and low education areas were associated with worse survival.

Landscape of germline mutations in 1144 patients (Pts) with gastrointestinal (GI) cancers

e13660

Background: The efficacy of PARP inhibitors in germline BRCA-mutated pancreatic adenocarcinoma (PC) and immune checkpoint inhibitors in dMMR colorectal cancer (CRC) shows the importance of genetic testing. We aimed to characterize the frequency of pathogenic/likely pathogenic germline variants (PLPVs) in GI cancer pts. Methods: A retrospective review of pts referred to the Levine Cancer Institute Genetics Program was conducted. Genetic testing used a focused hereditary cancer 4-43 gene panel or pan-cancer 82-84 gene panel. Results: Out of 1144 GI cancer pts seen between 2010 and 2019, 869 underwent germline testing, and 199 (23%) pts had at least one PLPV in a hereditary cancer susceptibility gene, while 253 (29.3%) had a variant of uncertain significance. Of 630 CRC pts, 24% had a PLPV and 13% harbored a germline mutation in DNA MMR genes and were diagnosed with Lynch Syndrome, representing ~50% of all pts with a PLPV. Other germline PLPVs were found in APC, ATM, BRCA1, BRCA2, CHEK2, MUTYH, and PALB2. Of 163 PC pts, 16.6% had a PLPV in ATM, BRCA2, CDKN2A, and MEN1. Gastric cancer pts (17%) had germline PLPVs in APC, BRCA2, CDH1, MLH1, and MSH2; biliary cancer pts (17%) had germline PLPVs in PALB2, RAD50, and PTCH1; and GIST pts (60%) had PLPVs in SDHA or SDHB. Conclusions: Germline mutations were found in 23% of GI cancer pts, underlining the importance of multigene germline testing. Knowledge of inherited GI cancer risk helps determine the likelihood of benefit from possible specific targeted therapies. Genetic testing and counseling pose a challenge, but implications for pts with hereditary syndromes are highly significant. [Table: see text]

Overcoming resistance to anti-PD1 and anti-PD-L1 treatment in gastrointestinal malignancies

In the last few years, the unprecedented results of immune checkpoint inhibitors have led to a paradigm shift in clinical practice for the treatment of several cancer types. However, the vast majority of patients with gastrointestinal cancer do not benefit from immunotherapy. To date, microsatellite instability high and DNA mismatch repair deficiency are the only robust predictive biomarkers of response to immune checkpoint inhibitors. Unfortunately, these patients comprise only 5%-10% of all gastrointestinal cancers. Several mechanisms of both innate and adaptive resistance to immunotherapy have been recognized that may be at least in part responsible for the failure of immune checkpoint inhibitors in this population of patients. In the first part of this review article, we provide an overview of the main clinical trials with immune checkpoint inhibitors in patients with gastrointestinal cancer and the role of predictive biomarkers. In the second part, we discuss the actual body of knowledge in terms of mechanisms of resistance to immunotherapy and the most promising approach that are currently under investigation in order to expand the population of patients with gastrointestinal cancer who could benefit from immune checkpoint inhibitors.

Molecular Analyses of Left- and Right-Sided Tumors in Adolescents and Young Adults with Colorectal Cancer

BACKGROUND

The incidence of colorectal cancer (CRC), particularly left-sided tumors (LT), in adolescents and young adults (AYA) is rising. Epigenetic events appear to play an important role in tumorigenesis and cancer progression, especially in younger patients. We compared molecular features of LT to right-sided tumors (RT) in AYA.

MATERIALS AND METHODS

A total of 246 LT and 56 RT were identified in a cohort of 612 AYA with primary CRC. Tumors were examined by next-generation sequencing (NGS), protein expression, and gene amplification. Tumor mutational burden (TMB) and microsatellite instability (MSI) were determined based on NGS data.

RESULTS

RT showed higher mutation rates compared with LT in several genes including BRAF (10.3% vs. 2.8%), KRAS (64.1% vs. 45.5%), PIK3CA (27% vs. 11.2%), and RNF43 (24.2% vs. 2.9%). Notably, additional mutations in distinct genes involved in histone modification and chromatin remodeling, as well as genes associated with DNA repair and cancer-predisposing syndromes, were characteristic of RT; most frequently KMT2D (27.8% vs. 3.4%), ARID1A (53.3% vs. 21.4%), MSH6 (11.1% vs. 2.3%), MLH1 (10.5% vs. 2.3%), MSH2 (10.5% vs. 1.2%), POLE (5.9% vs. 0.6%), PTEN (10.8% vs. 2.3%), and BRCA1 (5.4% vs. 0.6%). MSI was seen in 20.8% of RT versus 4.8% of LT. RT had a higher frequency of TMB-high regardless of MSI status.

CONCLUSION

Molecular profiling of AYA CRC revealed different molecular characteristics in RT versus LT. Epigenetic mechanisms and alteration in DNA repair genes warrant further investigation and may be a promising treatment target for CRC in AYA.

IMPLICATIONS FOR PRACTICE

Colorectal cancer (CRC) in adolescents and young adults (AYA) comprises a distinct entity with different clinicopathologic features and prognosis compared with older patients. Molecular profiling of right- and left-sided tumors in AYA is needed to gain novel insight into CRC biology and to tailor targeted treatment in this age group. This study found that right- and left-sided CRC show distinct molecular features in AYA, overall and in subgroups based on microsatellite instability status. Alterations in DNA double-strand break repair and homologous recombination repair, as well as epigenetic mechanisms, appear to play a critical role. The present molecular profiling data may support the development of personalized treatment strategies in the AYA population.

Evaluation of the change of outcomes over a 10-year period in patients with stage III colon cancer: pooled analysis of 6501 patients treated with fluorouracil, leucovorin, and oxaliplatin in the ACCENT database

BACKGROUND

Since 2004, adjuvant 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX or FLOX) have been the standard of care for patients with resected colon cancer. Herein we examine the change of outcomes over a 10-year period in patients with stage III colon cancer who received this regimen.

PATIENTS AND METHODS

Individual patient data from the ACCENT database was used to compare the outcomes in older (1998-2003) and newer (2004-2009) treatment eras for patients with stage III colon cancer who received adjuvant FOLFOX or FLOX. The outcomes were compared between the two groups by the multivariate Cox proportional-hazards model adjusting for age, sex, performance score, T stage, N stage, tumor sidedness, and histological grade.

RESULTS

A total of 6501 patients with stage III colon cancer who received adjuvant FOLFOX or FLOX in six randomized trials were included in the analysis. Patients enrolled in the new era group experienced statistically significant improvement in time to recurrence [3-year rate, 76.1% versus 73.0%; adjusted hazard ratio (HRadj) = 0.83 (95% CI, 0.74-0.92), P = 0.0008], disease-free survival (DFS) [3-year rate, 74.7% versus 72.3%; HRadj = 0.88 (0.79-0.98), P = 0.024], survival after recurrence (SAR) [median time, 27.0 versus 17.7 months; HRadj = 0.65 (0.57-0.74), P < 0.0001], and overall survival (OS) [5-year rate, 80.9% versus 75.7%; HRadj = 0.78 (0.69-0.88), P < 0.0001]. The improved outcomes remained in patients diagnosed at 45 years of age or older, low-risk patients (T1-3 and N1), left colon, mismatch repair proficient (pMMR), BRAF, and KRAS wild-type tumors.

CONCLUSION

Improved outcomes were observed in patients with stage III colon cancer enrolled in clinical trials who received adjuvant FOLFOX/FLOX therapy in 2004 or later compared with patients in the older era. Prolonged SAR calls for revalidation of 3-year DFS as the surrogate endpoint of OS in adjuvant clinical trials and reevaluation of optimal follow-up of OS to confirm the trial findings based on the DFS endpoints.

CLINICAL TRIALS NUMBERS

NCT00079274; NCT00096278; NCT00004931; NCT00275210; NCT00265811; NCT00112918.