Pre-diagnostic 25-hydroxyvitamin D in association with cancer specific- and all-cause mortality among low income, non-Hispanic Black Americans with colorectal cancer

Background: Observational studies show high pre-diagnosis 25-hydroxyvitamin D is associated with lower mortality after colorectal cancer (CRC) diagnosis. Results from clinical trials suggest vitamin D supplementation may improve outcomes among CRC patients. Most studies included few Black Americans, who typically have lower 25-hydroxyvitamin D. We evaluated associations between serum 25-hydroxyvitamin D and mortality after CRC diagnosis among Black American cases. Methods: Data arose from 218 Black Americans from the Southern Community Cohort Study diagnosed with CRC during follow-up (age 40-79 at enrollment). Pre-diagnostic 25-hydroxyvitamin D was measured at enrollment and categorized as deficient (<12 ng/mL), insufficient (12-19.9 ng/mL), or sufficient (≥20 ng/mL). Mortality was determined from the National Death Index. Cox proportional hazards were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between 25-hydroxyvitamin D and mortality. Results: As a continuous exposure, higher 25-hydroxyvitamin D was associated with overall mortality (HR=0.79 [0.65-0.96] per standard deviation increase, p-trend =.02) and CRC-specific mortality (HR=0.83 [0.64-1.08], p-trend =.16). For overall mortality, associations were strongest among females (HR=0.65 [0.42-0.92]), current smokers (HR=0.61 [0.38-0.98]), and obese participants (HR=0.47 [0.29-0.77]). Compared to those with deficiency, participants with sufficient 25-hydroxyvitamin D had lower overall mortality after multivariable adjustment (HR: 0.61 [0.37-1.01]). Conclusion: Pre-diagnosis 25-hydroxyvitamin D is inversely associated with overall and CRC-specific mortality among Black Americans with CRC. Correcting vitamin D deficiency may improve survival of these patients, particularly for obese individuals and smokers. Impact: Our results support including more Black Americans in trials of vitamin D supplementations to improve CRC outcomes.