Prognostic Impact of Palliative Primary Tumor Resection for Unresectable Stage 4 Colorectal Cancer: Using a Propensity Score Analysis

Background: The benefits that palliative resection of the primary tumor offers patients with unresectable stage 4 colorectal cancer, specifically with regard to overall survival, are controversial, and the issue is complicated by marked differences in patient backgrounds and characteristics. Methods: The study enrolled 770 consecutive patients with unresectable stage 4 colorectal cancer referred to the divisions of surgery or gastrointestinal oncology at the National Cancer Center Hospital from 1997 to 2013. Of these patients, 429 (56 %) underwent palliative resection of the primary tumor, whereas 341 (44 %) did not. To lessen the effects of confounding factors between the groups, including age, year, severe symptoms, number of organs involved by metastases, primary tumor site, and carcinoembryonic antigen (CEA) value, propensity score analyses were used for regression adjustment, stratification, and matching, with overall survival as the primary end point. Results: The regression adjustment including the propensity score as a linear predictor in the model showed that palliative resection was associated with a significantly improved overall survival (hazard ratio [HR] 0.60; 95 % confidence interval [CI] 0.50–0.71; p < 0.01)]. Stratification analysis showed that in all five strata, palliative resection was associated with better overall survival (HR 0.43–0.73). Similarly, the propensity score-matched cohort (267 matched pairs) yielded an HR of 0.58 (95 % CI 0.48–0.70; p < 0.01). Conclusions: The findings suggest that palliative resection of the primary tumor may be associated with improved overall survival. Further investigations such as prospective randomized trials are needed to confirm this result.