Somatic and germline mutation profiles of Chinese young colorectal cancer patients.

Abstract

e15522 Background: In recently years, although CRC morbidity and mortality can be mitigated through appropriate screening and surveillance, the incidence rate of colorectal cancer (CRC) younger than 50 years old increased annually. Limited studies have investigated the underpinnings driving CRC development in Chinese younger population. In our study, we aim to explore the comprehensive mutational profile of Chinese CRC patients old (＞50) and young (≤50) diagnosed with CRC. Methods: Targeted sequencing with a 539 cancer-related genes panel was performed on 235 patients diagnosed with CRC. We investigate the landscape and difference of old and young CRC somatic and germline mutations in our Chinese cohort and compare with TCGA CRC cohort (N = 592). Results: Analysis revealed an overall 20.9% (49/235) mutation detection rate of young CRC in our Chinese cohort, which is higher than TCGA cohort (13.9%, 82/592). In our cohort, all Chinese young CRC patients can detect mutation and median mutation count is 10 mutations which is similar to old CRC patients (11 mutations). Comparing high frequency somatic mutations (young group with top 20), we found that BRCA2 mutation in young CRC group is significantly higher than old group (18.4% vs 7.0%, P = 0.025). In TCGA cohort, there is no difference between two groups with top 20 mutations and frequency of BRCA2 is 13.4% (11/82) in young CRC. For germline mutation, 12.29% (29/236) patients in our Chinese cohort harbored pathogenic and likely pathogenic (P/LP) germline mutations and 24.1% (7/29) CRC with P/LP germline mutations is young patients. In these seven P/LP mutation young patients, three patients have MMR gene mutation, two patients harbor ATM mutation, one patient has APC and another has SLX4 mutation. Moreover, young CRC have higher frequency MSI-H than old CRC patients (28.6% vs 18.2%). Conclusions: Our study has identified that young CRC patients account for a higher proportion in Chinese population and BRAC2 mutation may be an important factor in the early development of colorectal tumors in younger patients. In addition, our results also support the role of MSI statues in tumor oncogenesis in Chinese patients with early-onset CRC, indicating the need to include a more comprehensive germline mutation and genetic screening in our population.