Clinicopathologic implications of DNA mismatch repair status in endometrial carcinomas

Abstract Objective Endometrial carcinoma is the most common malignancy in women with Lynch syndrome caused by mismatch repair (MMR) deficiency. We investigated the clinicopathologic significance of deficient MMR and Lynch syndrome presumed by MMR analyses in unselected endometrial carcinomas. Methods We analyzed immunohistochemistry of MMR proteins (MLH1/MSH2/MSH6/PMS2) and MLH1 promoter methylation in primary endometrial carcinomas from 221 consecutive patients. Based on these results, tumors were categorized as sporadic or probable Lynch syndrome (PLS). Clinicopathologic variables and prognosis were compared according to MMR status and sporadic/PLS classification. Results Deficient MMR showed only trends towards favorable overall survival (OS) compared with intact MMR (p=0.13), whereas PLS showed significantly better OS than sporadic (p=0.038). Sporadic was significantly associated with older age, obesity, deep myometrial invasion, and advanced stage (p=0.008, 0.01, 0.02 and 0.03), while PLS was significantly associated with early stage and Lynch syndrome-associated multiple cancer (p=0.04 and 0.001). The trend towards favorable OS of PLS was stronger in advanced stage than in early stage (hazard ratio, 0.044 [95% CI 0–25.6] vs. 0.49 [0.063–3.8]). In the subset receiving adjuvant therapies, PLS showed trends towards favorable disease-free survival compared to sporadic by contrast with patients receiving no adjuvant therapies showing no such trend (hazard ratio, 0.045 [95% CI 0–20.3] vs. 0.81 [0.095–7.0]). Conclusions The current findings suggest that analyzing MMR status and searching for Lynch syndrome may identify a subset of patients with favorable survival and high sensitivity to adjuvant therapies, providing novel and useful implications for formulating the precision medicine in endometrial carcinoma.