Deficient DNA mismatch repair status reveals good prognosis for non-metastatic signet ring cell (SRC) subpopulation

Purpose As a rare subpopulation of colorectal cancer (CRC), signet ring cell carcinoma (SRCC) has poor prognosis. The prognostic role of DNA mismatch repair (MMR) has been seldom studied. Thus, to analyze the effect of MMR status on survival outcomes in colorectal SRCC patients, we conducted this retrospective study. Method DNA mismatch repair status was performed on 114 patients via IHC. Prognostic clinicopathologic parameters of deficient or proficient DNA mismatch repair status were compared by the chi-squared test . Survival outcomes (OS, DFS) were measured via the Kaplan-Meier LIFETEST and the log-rank test . The multivariate survival analysis was evaluated by the Cox proportional-hazards regression model , and the hazard ratio (HR) with 95% CI was provided. Results Among 7343 colorectal cancer patients from 2009 to 2020, there were 176 patients with SRCC, nearly one quarter (23.7%, 27/114) harbored dMMR. Besides, dMMR SRCC patients are more often located in the rectum (51.1%). No difference was found for metastatic disease while dMMR had relatively good prognosis for non-metastatic with a median follow-up of 71.9 months (13.9 to 155). The overall 3- and 5-year OS were 42.1% and 32.1%, respectively, while the 3- and 5-year DFS were 43.0% and 32.9%, respectively. Moreover, the multivariate survival analysis via Cox proportional-hazards model revealed MMR status was an independent prognostic for colorectal SRCC. Conclusion Nearly one quarter patients harbored dMMR and relatively better survival outcomes than pMMR in this colorectal SRCC cohort. Early identification of this subgroup may be of importance for the survival of SRCC patients.