Left-sided primary tumor is a favorable prognostic factor for metastatic colorectal cancer patients receiving surgery.

ABSTRACT

OBJECTIVE: The role of surgery in metastatic colorectal cancer (mCRC) remains controversial. This study was performed to assess the impact of surgery on survival in metastatic colorectal cancer. MATERIALS AND METHODS: Information of mCRC patients diagnosed between January 1, 2004, and December 31, 2013, was retrieved from the Surveillance, Epidemiology, and End Results Program database. Patients were classified in three groups patients undergoing resection of both primary and distant metastatic tumors (group 'PMTR'), patients receiving primary tumor resection alone (group 'PTR') and patients not undergoing any surgery (group 'No resection'). Kaplan-Meier method and multivariate Cox proportional hazard regression analysis were applied to estimate disease specific survival time (DSS) and determine prognostic factors. RESULTS: A total of 38,591 mCRC patients were eligible. Overall, median DSS of group 'PMTR' was significantly longer compared with group 'PTR' and group 'No resection' (28.0 vs 21.0 vs 11.0 months, P < 0.001). Stratified analysis observed that primary tumor in left-sided colorectal cancer (LCRC) was a favorable prognostic factor compared with right-sided colorectal cancer (RCRC) (median DSS of LCRC PMTR, 34 months, PTR, 25 months, No resection, 13 months; median DSS of RCRC PMTR, 20 months, PTR, 16 months, No resection, 8 months; P < 0.001). Multivariate analysis demonstrated that surgery was an independent prognostic factor for better survival (PMTR, HR = 0.403, 95% CI 0.384-0.423, P < 0.001; PTR, HR = 0.515, 95% CI 0.496-0.534, P < 0.001). Furthermore, in patients undergoing surgery, patients with younger age, female, married status, LCRC and lower CEA level were prone to receiving PMTR. CONCLUSIONS: This analysis demonstrated that surgery was an independent prognostic factor for improved survival in mCRC. Patients with LCRC had better survival than patients with RCRC after surgery.