Benefit of Surgical Resection of the Primary Tumor in Patients Undergoing Chemotherapy for Stage IV Colorectal Cancer with Unresected Metastasis.

PURPOSE

Resection of the primary tumor in patients with unresected metastatic colorectal cancer is controversial, and often performed only for palliation of symptoms. Our goal was to determine if resection of the primary tumor in this patient population is associated with improved survival.

METHODS

This is a retrospective cohort study of the National Cancer Data Base from 2004 to 2012. The study population included all patients with synchronous metastatic colorectal adenocarcinoma who were treated with systemic chemotherapy. The study groups were patients who underwent definitive surgery for the primary tumor and those who did not. Patients were excluded if they had surgical intervention on the sites of metastasis or pathology other than adenocarcinoma. Primary outcome was overall survival.

RESULTS

Of the 65,543 patients with unresected stage IV colorectal adenocarcinoma undergoing chemotherapy, 55% underwent surgical resection of the primary site. Patients who underwent surgical resection of the primary tumor had improved median survival compared to patients treated with chemotherapy alone (22 vs 13 months, p < .0001). The surgical survival benefit was present for patients who were treated with either multi-agent or single-agent chemotherapy (23 vs 14 months, p < 0.001; 19 vs 9 months, p < 0.001). Surgical resection of the primary tumor was also associated with improved survival when using multivariate analysis with propensity score matching (OR = 0.863; 95% CI [0.805-.924]; HR = 0.914; 95% CI [0.888-0.942]).

CONCLUSIONS

Our results show that in patients with synchronous unresected stage IV colorectal adenocarcinoma undergoing single- or multi-agent chemotherapy, after adjusting for confounding variables, definitive resection of the primary site was associated with improved overall survival. Large randomized controlled trials are needed to determine if there is a causal relationship between surgery and increased overall survival in this patient population.