Effectiveness of a vitamin D regimen in deficient multiple myeloma patients and its effect on peripheral neuropathy

Peripheral neuropathy (PN) is common in multiple myeloma (MM) patients. More insight has been gained concerning the role of vitamin D in preventing PN. However, studies evaluating the effects of vitamin D₃ supplementation on PN are lacking. The aims of this study are to (1) evaluate the effectiveness of a vitamin D₃ regimen on achieving adequate vitamin D levels in deficient MM patients and to (2) exploratively evaluate the effect of vitamin D₃ supplementation on PN.

Thirty-nine MM patients with inadequate (< 75 nmol/L [= 30 ng/mL]) 25-hydroxyvitamin D (25(OH)D) levels were included in this multicenter, prospective, single-arm study, of whom 35 patients completed the study. They received oral vitamin D₃ for 6 months according to a dose escalation regimen that consisted of one or two loading doses of 200,000 international units (IU), and maintenance doses of 800, 1600, or 3200 IU/day depending on the 25(OH)D level. A validated questionnaire was used to measure PN.

Median 25(OH)D increased from 38 (IQR 32-52) nmol/L at baseline to 77 (IQR 72-87) nmol/L after 6 months (P < 0.001). Adequate 25(OH)D levels were achieved by 66% of the subjects, and 34% were within the range of 50-75 nmol/L. Furthermore, in 37% of the participants, PN severity decreased (P = 0.007).

The use of substantially higher vitamin D₃ doses than recommended in current guidelines resulted in a significant increase in vitamin D levels in MM patients. Furthermore, evaluation of PN showed a significant decrease in PN grading. However, this exploratory evaluation needs further confirmatory research.