Background Observational studies have suggested that 25-hydroxyvitamin D [25(OH)D] is associated with better outcomes in patients with malignant melanoma (MM).
Objectives To study the relationship between serum 25(OH)D levels and clinical parameters in a large German cohort of patients with MM.
Methods We prospectively investigated the 25(OH)D serum levels of 764 patients with MM using the direct competitive chemiluminescence LIAISON® immunoassay. Patients with MM who were taking 25(OH)D supplements were not included.
Results Median serum 25(OH)D baseline levels were 12·3 ng mL−1 (lower quartile: 7·3 ng mL−1, upper quartile: 20·2 ng mL−1). Of the 764 patients, 564 (73·8%) had 25(OH)D deficiency [25(OH)D < 20 ng mL−1], 145 (18·8%) had 25(OH)D insufficiency [25(OH)D ≥ 20, < 30 ng mL−1] and only 55 (7·2%) had serum 25(OH)D levels within the normal range (≥ 30 ng mL−1). Using a multiple regression model, lower 25(OH)D levels were significantly associated with higher Breslow tumour thickness (class: < 1 mm; 1–4 mm; > 4 mm, regression coefficient −1·45, P = 0·028) and higher American Joint Committee on Cancer 2002 melanoma stage (regression coefficient: −0·79, P = 0·036).
Conclusions In patients with MM, decreased 25(OH)D serum levels are associated with increased tumour thickness and advanced tumour stage. Hence, evidence is accumulating that patients with MM might benefit from 25(OH)D supplements.