A prospective clinical trial of cholecalciferol 2000 IU/day in colorectal cancer patients: Evidence of a chemotherapy-response interaction

Background: We have previously reported a negative correlation between the effect of chemotherapy and 25-hydroxy vitamin D ₃ (25-D ₃) levels in patients with colorectal cancer. Based on this finding, we hypothesized that the response to vitamin D ₃ supplementation may be attenuated in patients with colorectal cancer. Aim: To determine 25-D ₃ response to 2000 IU/day vitamin D ₃ supplementation in patients with colorectal cancer. Materials and Methods: Fifty evaluable colorectal cancer patients were treated with vitamin D ₃ at 2000 IU/day for 6 months. Serum 25-D ₃ levels were measured at baseline, 3, and 6 months of supplementation. Results: The mean 25-D ₃ level was 17.5 ng/ml at baseline, 31.6 ng/ml at 3 months, and 33.8 ng/ml at 6 months. The most important factor in determining 25-D ₃ response was chemotherapy status. A rise in 25-D ₃ of ≥W ng/ml at the 3-month interval was observed in 92% of chemotherapy-free patients vs. 39% of chemotherapy patients. Similar differences in response were noted at the 6-month interval. Conclusion: Depressed 25-D ₃ levels are common in patients with colorectal cancer. Active chemotherapy is associated with an attenuated response to 2000 IU of D ₃ supplementation in this patient population. Alternative vitamin D ₃ dosing schedules need further investigation in colorectal cancer patients undergoing chemotherapy.