Vitamin D levels among patients with colorectal cancer (CRC) from the San Francisco Bay area.

Abstract

793 Background: A growing body of literature suggests that 25-hydroxyvitamin D [25(OH)D] levels are inversely related to the risk of developing CRC and that deficiency is associated with CRC-specific mortality. Due to the unique racial-ethnic diversity and UV exposure patterns of the San Francisco Bay Area, we aimed to evaluate vitamin D levels among our CRC patients at time of diagnosis and during treatment. Methods: Permanent residents of the SF Bay Area with a new diagnosis of CRC of any stage were recruited between 2011 and 2015 prior to initiation of therapy. Self-reported data on sun exposure, diet, and exercise patterns were collected. Clinical data including disease stage and primary tumor location were abstracted from charts. Serum 25(OH)D levels at time of diagnosis and at 6-month follow-up were batched and measured using the Liaison XL assay (Heartland Assays). Supplement use was not restricted. Kruskal-Wallis and Pearson correlation tests were used for categorical or continuous variables, respectively, to evaluate the associations of patient characteristics with 25(OH)D levels. Results: Among 94 patients with a new diagnosis of CRC, median 25(OH)D level at baseline was 27.0 ng/mL (range 7.2-59.0); 26% had deficient levels (<20 ng/mL), 39% had insufficient levels (<20 and <30 ng/mL), and 35% had sufficient levels (<30 ng/mL). Race, multivitamin use, vitamin D supplementation, and disease stage were associated with baseline serum 25(OH)D levels (p<0.05). The median change in 25(OH)D from baseline to six months was -0.6 ng/mL (range -19.4-51.7) for patients treated with chemotherapy (n=60) and 1.6 ng/mL (range -6.4-33.2) for patients who did not receive chemotherapy (n=19) (p=0.51). Conclusions: Among patients with a new diagnosis of CRC in the San Francisco Bay area, vitamin D insufficiency was seen in more than half of patients, consistent with reports from other geographic areas. Allowing for vitamin D supplementation, serum 25(OH)D levels did not decrease significantly after 6 months of chemotherapy. We are routinely screening CRC patients for 25(OH)D insufficiency at time of diagnosis and during treatment.