The correlation between mismatch repair status and clinicopathological characteristics in Chinese colorectal cancer patients.
544 Background: Our study aimed to explore the relationship between mismatch repair (MMR) status and clinicopathological characteristics in Chinese patients with colorectal cancer (CRC). Methods: A total of 2684 patients with histologically confirmed adenocarcinoma of CRC were consecutively recruited between May 2011 and May 2015 at Sun Yat-sen University cancer center. The exclusion criteria included multiple primary tumors, synchronous and metachronous CRC, and familial adenomatous polyposis. The CRC was defined as left colon with the tumor located below the splenic flexure or rectum, otherwise grouped as right colon. Correlations of MMR status and patient’s demographics, tumor characteristics and TNM staging (exclude 315 CRC patients receiving neoadjuvant therapy) were investigated. Results: We found that deficient MMR (dMMR) status was more likely detected in younger CRC patients compared to the the elderly (12.7% vs 7.5%, P < 0.001). The dMMR rate in right colon cancer was significantly higher than that in left colon cancer and rectal cancer (22.7% vs 7.2% vs 5.2%, P < 0.001).With respect to tumor differentiation, we found that the mucinous adenocarcinoma had the highest rate of dMMR(24.4%), followed by poorly differentiated adenocarcinoma(18.5%), signet-ring cell carcinoma(17.6%), well differentiated adenocarcinoma(9.5%), moderately differentiated adenocarcinoma(8.9%), and neuroendocrine carcinoma (0%) ( P < 0.001). In addition, the proportions in stage I, stage II, stage III and stage IV CRC were 9.7%, 16.5% , 8.5% and 3.9%, respectively ( P < 0.001). There was no significant difference in gender (P = 0.114). Conclusions: At the first time, our study demonstrated that dMMR status was most likely detected at younger age (less than 59 years) and stage II right colon mucinous adenocarcinoma in large volume Chinese patients, which was similar to the results in western countries.