Low 25-hydroxyvitamin D levels in people with a solid tumor cancer diagnosis: the tip of the iceberg?

Low serum 25-hydroxyvitamin D [25(OH)D] levels have been linked to both cancer incidence and poor prognosis. The frequency of 25(OH)D tests and clinical factors associated with low levels in cancer patients are unknown. Electronic medical records from 2006 to 2007 of 39,252 adult solid tumor patients were reviewed. Data included demographics, cancer sites (primary and metastatic), and first serum 25(OH)D level during the study period. Laboratory data, comorbidities, selected medications, and anticancer treatment within the prior 2 months were recorded. Data were compared between (1) those tested and not tested and (2) 25(OH)D levels a parts per thousand currency sign10 ng/ml (deficient), 11-30 ng/ml (insufficient), and a parts per thousand yen31 ng/ml (sufficient). Stepwise logistic regression identified independent predictors of low serum 25(OH)D levels. The cohort was 86 % Caucasian and 48 % female with a mean age of 63 +/- 14 years (mean +/- SD). The most prevalent cancer was breast (19 %). In total, 2,098 (5 %) had a 25(OH)D test. Of those tested, 133 (6 %) had levels a parts per thousand currency sign10 ng/ml and 1,311 (62 %) 11-30 ng/ml. Tests were more frequent in females and in those with breast, skin, and thyroid cancers (P < 0.001). Low 25(OH)D levels were associated (in univariable analyses) with male gender, non-Caucasian race, gastrointestinal tumor primary sites, metastatic disease, benign liver disease, low serum albumin, and elevated liver enzymes. Significant factors in multivariable models for 25(OH)D levels a parts per thousand currency sign10 and a parts per thousand currency sign30 ng/ml included non-Caucasian race, primary cancer site, and test calendar month. Vitamin D supplements and recent antineoplastic medication were associated with sufficient levels. Low (deficient or insufficient) 25(OH)D serum levels were highly prevalent in people with solid tumors. Vitamin D tests were infrequent and paradoxically less often done in high-risk groups. Tests were more frequent in females and in those with breast, skin, and thyroid cancers. Further research should examine role of routine 25(OH)D tests, the clinical consequences of low levels, and therapeutic supplementation in people with cancer.