Impact of Adjuvant Chemotherapy in Patients With Curatively Resected Stage IV Colorectal Cancer

The aim of this study was to investigate the impact of adjuvant chemotherapy on survival of patients who had curative resection for stage IV colorectal cancer. The efficacy of adjuvant chemotherapy after curative resection for stage IV colorectal cancer remains unclear. The database of 3695 patients with stage IV colorectal cancer between 1991 and 2007 collected from 16 member hospitals of the Japanese Society for Cancer of the Colon and Rectum was used for this investigation. The survivals of patients with and without adjuvant chemotherapy after curative resection for stage IV colorectal cancer were evaluated using a propensity score matching method. The data of 689 patients who underwent curative resection for both primary and synchronous metastatic tumors were extracted from the database and used for analysis in this study. The 5- year overall survival rates of the patients with and without adjuvant chemotherapy were 41.8% and 33.9%, respectively. A Cox proportional hazards model showed that adjuvant chemotherapy (P = 0.0042), regional lymph node metastasis (P < 0.0001), and peritoneal metastasis (P = 0.0006) were independent factors for overall survival. In the propensity scorematched cohort, patients with adjuvant chemotherapy had better overall survival than those without (P = 0.026). The present study demonstrated that adjuvant chemotherapy improved overall survival after curative resection for stage IV colorectal cancer. The efficacy of each chemotherapeutic regimen in the adjuvant setting for stage IV colorectal cancer should be clarified in the future.