Prognostic Impact of Mucinous Adenocarcinoma in Stage II and III Colon Cancer

BACKGROUND: Mucinous adenocarcinoma is a rare histologic feature of colorectal cancer and is characterized by oncologic features that are different from those of adenocarcinoma. However, there are conflicting views regarding the prognostic impact of mucinous adenocarcinoma on colon cancer. OBJECTIVE: This study aimed to evaluate the prognostic impact of mucinous adenocarcinoma in stage II and III colon cancer. DESIGN: This was a retrospective cohort study. SETTINGS: This study was conducted between January 2010 and December 2015. Patients were divided into the mucinous adenocarcinoma and nonmucinous adenocarcinoma groups. Disease-free survival and overall survival were assessed using propensity score matching. PATIENTS: Overall, 2532 patients who underwent radical surgery for stage II and III colon cancer were included in the study. MAIN OUTCOME MEASURES: The main outcome measures were disease-free survival and overall survival. RESULTS: The median follow-up duration was 86 months. The disease-free survival and overall survival were significantly lower in the mucinous adenocarcinoma group than in the nonmucinous adenocarcinoma group. In subgroup analysis, there was no significant difference in the disease-free survival and overall survival between patients with and without mucinous adenocarcinoma with stage II colon cancer. In stage III colon cancer, the disease-free survival and overall survival were significantly lower in patients with mucinous adenocarcinoma than in those without mucinous adenocarcinoma. Multivariable analysis showed that mucinous adenocarcinoma was a poor prognostic factor for disease-free survival and overall survival. LIMITATION: The study's limitations include those that are inherently associated with retrospective single-center studies. CONCLUSIONS: Mucinous adenocarcinoma is a poor prognostic factor in stage III but not in stage II colon cancer. Therefore, mucinous adenocarcinoma might not be regarded as an independent risk factor requiring chemotherapy for favorable oncologic outcomes. However, for stage III colon cancer, patients with mucinous adenocarcinoma require close observation.