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

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.