Vitamin D status and survival of metastatic colorectal cancer patients: Results from CALGB/SWOG 80405 (Alliance).

507 Background: Prospective epidemiologic data suggest that higher levels of 25-hydroxyvitamin D [25(OH)D] are associated with improved survival in patients with colorectal cancer (CRC), however, the relationship between 25(OH)D and outcome in metastatic CRC, specifically, is unknown. Methods: We prospectively assessed the association between plasma 25(OH)D and overall survival (OS) in previously untreated metastatic CRC patients enrolled in CALGB 80405, a randomized phase III trial of chemotherapy + bevacizumab, cetuximab, or both, prior to the KRAS WT amendment. Progression-free survival (PFS) was a secondary endpoint. Plasma 25(OH)D levels were measured at baseline by radioimmunoassay, and dietary and lifestyle behaviors collected from self-administered questionnaires. Cox proportional hazards models were used to calculate hazard ratios adjusted for other prognostic factors. In sensitivity analyses, patients who died within 3 or 6 months of blood draw were excluded to address the possibility of reverse causation. Results: Among 1,043 patients, median plasma 25(OH)D was 17.2 ng/mL (range 2.2-72.7). Older and black patients, those with lower dietary and supplemental vitamin D intake, ECOG performance status 1 (vs. 0), higher body-mass index, lower physical activity, and blood draws during the winter and spring had significantly lower levels of 25(OH)D. Patients in the highest quintile of 25(OH)D had significantly improved OS compared to those in the lowest after adjusting for pathologic and clinical prognostic factors (median 32.6 vs. 24.5 months; HR 0.67, 95% CI, 0.53-0.86; p trend 0.002). Increasing concentrations of 25(OH)D were also associated with improved PFS (median 12.2 vs. 10.1 months; HR 0.80, 95% CI, 0.64-1.01; p trend = 0.02). The results were consistent across subgroups of patient characteristics, including KRAS status, and remained unchanged after excluding patients who died within 3 or 6 months of blood draw. Conclusions: Higher concentrations of plasma 25(OH)D are associated with significantly improved survival in metastatic CRC patients treated with chemotherapy + biologics. Randomized trials of vitamin D supplementation are warranted and are currently underway.

Duke Scholars

Author Donna Niedzwiecki Biostatistics & Bioinformatics, Division of Biostatistics