Effectiveness of oral fluoropyrimidine monotherapy as adjuvant chemotherapy for high-risk stage II colon cancer

PURPOSE: The benefit of adjuvant chemotherapy for stage II colon cancer has not been clearly demonstrated even in cases with high-risk factors. This study aimed to compare the effectiveness of oral fluoropyrimidine monotherapy as adjuvant chemotherapy with that of intravenous fluoropyrimidine-based chemotherapy for high-risk stage II colon cancer. METHODS: This single-institution, retrospective study included patients who underwent curative resection for high-risk stage II colon cancer between 2003 and 2014. Patients were classified into 3 postoperative treatment groups: observation, oral fluoropyrimidine monotherapy group (OG), or intravenous fluoropyrimidine-based chemotherapy group (IVG). RESULTS: We identified 356 patients, including 87 (24.4%) in the observation group, 172 (48.3%) in the OG, and 97 (27.2%) in the IVG. Patients in the OG were older (63.8 ± 10.7 vs. 56.5 ± 10.8, P < 0.001) and had a lower number of T4 lesions (12.8% vs. 35.1%, P < 0.001) than those in the IVG. Regarding survival outcomes, the 5-year overall and disease-free survival rates were not different between the OG and IVG (91.2% vs. 92.6% [P = 0.090] and 85.1% vs. 81.9% [P = 0.535], respectively). In multivariate analysis, age over 70 years and no adjuvant chemotherapy were associated with poor overall survival and disease-free survival. Fewer chemotherapy-related adverse events of grade ≥3 were observed in the OG than in the IVG (12.2% vs. 34.0%, P < 0.001). CONCLUSION: In high-risk stage II colon cancer, adjuvant oral fluoropyrimidine monotherapy can be an effective and convenient alternative to intravenous fluoropyrimidine-based chemotherapy as it has comparable oncological outcomes and reduced chemotherapy-related complications.