Right- and left-sided stage III colon cancers present different prognostic outcomes of oxaliplatin-based adjuvant chemotherapy after curative resection.

Background: Growing evidence has suggested that right-sided colon cancer (RCC) and left-sided colon cancer (LCC) should be considered as different tumor entities. However, stage III colon cancer is currently treated as the same entity with uniform therapy. This study was aimed at investigating the prognostic influence of tumor location in patients with stage III colon cancer receiving adjuvant chemotherapy after curative resection.

Patients And Methods: We retrospectively analyzed 274 eligible patients with stage III colon cancer undergoing curative tumor resection followed by adjuvant chemotherapy with oxaliplatin and capecitabine between December 2007 and December 2013. Disease-free survival (DFS) and overall survival (OS) were analyzed using Kaplan-Meier and log-rank tests, and prognostic factors were identified by Cox regression methods.

Results: Patients with RCC exhibited lower hemoglobin levels (23.6% vs. 9.8%; = 0.002), larger tumor size (60.6% vs. 40.9%; = 0.001), and a higher proportion of 12 or more resected lymph nodes (86.4% vs. 64.6%; < 0.001) than patients with LCC. Grade 1 neurotoxicity was more common in patients with RCC than in those with LCC (53.6% vs. 40.9%; = 0.037). RCC was significantly associated with a shorter 3-year OS than LCC, whereas a difference was noted only for stage IIIC and not stage IIIA or stage IIIB colon cancer. Multivariate analyses revealed that RCC was independently associated with a worse 3-year OS (hazard ratio: 2.213; 95% CI: 1.063-4.606; = 0.002). In addition, an increase in 3-year OS and DFS after 6-8 cycles of adjuvant chemotherapy was only observed in patients with RCC and not in those with LCC.

Conclusion: This study indicated that RCC has a worse prognostic outcome for stage III colon cancer, and a full course of adjuvant chemotherapy should be suggested for patients with RCC.