Survival outcome of palliative primary tumor resection for colorectal cancer patients with synchronous liver and/or lung metastases: A retrospective cohort study in the SEER database by propensity score matching analysis

Background: There is a great matter of controversies whether some of these synchronous metastatic colorectal cancer patients can benefit from palliative primary tumor resection (pPTR) and there is still no reported randomized control trial to address this issue. Methods: Patients with microscopically proven metastatic colorectal cancer were identified within the SEER database (2010-2016). Patients were propensity matched 1:1 into pPTR and non-surgery groups and among the matched cohort, the univariable and multivariable Cox proportional hazards regression models were performed to identify predictors of survival. Median survival was calculated by using the Kaplan-Meier method. Results: Of 21,405 colorectal cancer patients diagnosed with synchronous liver and/or lung metastases, 7386 were identified in the matched cohort. The median overall survival was 12.0 months, 22.0 months in the nonsurgery, surgery groups, respectively (p < 0.001) and the corresponding median cancer-specific survival was 13.0 months, 22.0 months, respectively (p < 0.001). Multivariable Cox regression analysis demonstrated that surgery was independently associated with improved overall survival (hazard ratio, 0.531) as well as cancerspecific survival (hazard ratio, 0.516). In stratified analyses by primary site and patterns of distant metastases, those patients with pPTR had better prognosis. In addition, stratified analysis revealed that trimodality therapy was linked with the greatest therapeutic effect followed by addition of chemotherapy to pPTR. Conclusions: pPTR may offer some therapeutic benefits among carefully selected patients, and surgery-based multimodality therapy was associated with better survival.