Analysis of reduced-dose administration of oxaliplatin as adjuvant FOLFOX chemotherapy for colorectal cancer

Purpose: An oxaliplatin-based regimen is the most common adjuvant chemotherapy for patients with stage II/III colorectal cancer, but many patients experience dose reduction or early termination of chemotherapy due to side effects. We conducted this study to verify the range of reduction with oncologic safety. Methods: Patients with stage II/III colorectal cancer who received adjuvant FOLFOX chemotherapy were enrolled in this study. The total amount of oxaliplatin administered per patient was calculated as a percentile based on 12 cycles of full-dose FOLFOX as a standard dose. The cutoff values showing significant differences in survival were calculated, and the clinicopathologic outcomes of patient groups classified by the value were compared. Results: Among a total of 611 patients, there were 107 stage II patients, and 504 stage III patients. At 60% of the standard dose of oxaliplatin, the patients in the dose reduction group were older (62 years vs. 58 years, P = 0.003), had lower body mass index (BMI) (23.1 kg/m² vs. 24.0 kg/m², P = 0.005), and were more exposed to neoadjuvant treatment (18.0% vs. 9.1%, P = 0.003) in comparison to the standard group. At 60% of the standard dose, there were no significant differences in 5-year disease-free survival (DFS) and overall survival (OS) between the 2 groups (5-year DFS: 73.5% vs. 74.2%, P = 0.519; 5-year OS: 71.9% vs. 81.5%, P = 0.256, respectively). Conclusion: Patients with old age, low BMI, and more frequent exposure to neoadjuvant treatment tended to show lower compliance with chemotherapy. More than 60% dose should be administered to patients with stage II/III colorectal cancer as adjuvant chemotherapy to achieve acceptable oncologic outcomes.