Adjuvant chemotherapy improves prognosis of resectable stage IV colorectal cancer: a comparative study using inverse probability of treatment weighting

BACKGROUND: Adjuvant chemotherapy (AC) is known to be beneficial for stage III colorectal cancer (CRC). In contrast, only a few studies have reported the survival benefits of AC for stage IV CRC after curative surgery. METHODS: We identified 155 CRC patients with various organ metastases who underwent curative surgery in our hospital between 2003 and 2017. Clinicopathological parameters and postoperative AC were reviewed. Multivariate analyses were performed to identify prognostic factors. Moreover, the effects of AC on recurrence-free survival (RFS) and overall survival (OS) were analyzed using inverse probability of treatment weighting. RESULTS: The cohort comprised 94 males and 61 females, with a mean age of 63 years. AC was administered to 57% of patients who underwent surgery between 2003 and 2010 and 76% between 2011 and 2017 (p = 0.015). AC was more likely administered to patients with a good performance status, high preoperative albumin level, regional node and peritoneal metastases, and no intraoperative blood transfusion. Multivariate analyses identified AC as a significant prognostic factors for RFS and OS [hazard ratio (HR): 1.86, p = 0.003, and 2.66, p = 0.002, respectively]. After adjusting for different backgrounds, 5-year RFS and OS rates were higher in patients receiving AC (27% and 67%) than in those without AC (14% and 46%, p < 0.0001 and p = 0.0005). Subgroup analyses showed that AC significantly improved RFS in node-negative patients (HR: 2.16, p = 0.029), and RFS and OS in node-positive patients (HR: 2.03, p < 0.0001, and 2.02, p = 0.001, respectively). CONCLUSION: AC can be discussed with resectable stage IV CRC patients because of its significant survival-improving effects.