Genomic analysis of recurrent early stage and de novo metastatic colorectal cancer among veterans.

Abstract

e15593 Background: The Veterans Health Administration (VHA) diagnoses approximately 4,000 cases of colon cancer each year and conducts Next Generation Sequencing (NGS) on recurrent and metastatic cases. The molecular profile of cancers resected for cure that recur is poorly characterized and holds promise to clarify both the risk and mechanisms of recurrence. We sought to characterize these genetic differences. Methods: A national database from the VHA consisting of colon cancer patients was analyzed for those with recurrent disease who have received NGS testing from 2015-2021. Data was analyzed by stage and presence of DNA mismatch repair (MMR) (MLH1, MSH2, PMS2, MSH6) and DNA damage repair (DDR) abnormalities (BRCA1, BRCA2, ATM, BRIP1, BARD1, CDK12, CHEK1, CHEK2, FANCL, PALB2, RAD51B, RAD51C, RAD51D) in addition to receipt of chemotherapy and overall survival with univariate and multivariate cox proportional hazards analyses and multivariate logistic regression analyses. Chi squared analyses were also performed comparing presence of DNA abnormalities between early recurrent and stage IV cancers. Results: From309,318 cases with colon cancer codes, we identified 2,366 colon cancer patients who had NGS and had recurrent or de novo metastatic disease. 1,072 patients had initial staging annotated (I n = 89, II n = 194, III n = 320 , IV n = 453). The average age was 69.41 years; 70.5% white, 21.5% Black and 7.8% other. Among all patients, DNA MMR abnormalities (n = 117) were associated with better overall survival, after controlling for age and race (HR 0.6, 95% CI 0.42-0.85, p < 0.005). Among recurrent early stage (I-III) and stage IV patients, MMR (n = 55 and n = 21, respectively) is associated with improved survival in multivariable models (HR 0.39, 95% CI 0.33-0.46, p < 0.001) . Among the 4 DNA MMR genes, MSH2 mutations had the strongest association with survival (univariate HR 0.31, 0.15-0.62, p < 0.001). Among patients with MMR abnormalities, those who received either only capecitabine or only fluorouracil (without irinotecan or oxaliplatin) had worse overall survival (HR 2.6, 1.34 -5.04, p < 0.005). This effect was more pronounced in early stage recurrent patients versus patients with de novo metastatic disease (HR 5.1, 1.87 – 13.9, p < 0.001). Finally, we also found that early stage patients with recurrent disease are more likely to have MMR abnormalities compared to de novo metastatic (8.8% vs 4.6%, p < 0.01) and confirmed this finding after controlling for race and age. (OR 2.13, p < 0.005). Conclusions: Among Veteranswith colon cancer, resected recurrent colon cancer is more likely to have DNA MMR abnormalities than de novo metastatic disease. Veterans with recurrent and or metastatic disease with DNA MMR have better outcomes regardless of stage at diagnosis. These findings suggest different pathogenesis for those with recurrent disease after curative resection, and for those with de novo metastatic disease.