Supplementary Table S3: Power analyses for Cox-proportional hazards models concerning the associations between serum 25-hydroxyvitamin D and mortality outcomes, with adjustment for mortality risk factors
ARTICLE ABSTRACT
Observational studies show high prediagnosis 25-hydroxyvitamin D is associated with lower mortality after colorectal cancer diagnosis. Results from clinical trials suggest vitamin D supplementation may improve outcomes among patients with colorectal cancer. Most studies included few Black Americans, who typically have lower 25-hydroxyvitamin D. We evaluated associations between serum 25-hydroxyvitamin D and mortality after colorectal cancer diagnosis among Black American cases.
Data arose from 218 Black Americans from the Southern Community Cohort Study diagnosed with colorectal cancer during follow-up (age 40–79 at enrollment). Prediagnostic 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 HRs and 95% confidence intervals (CI) for associations between 25-hydroxyvitamin D and mortality.
As a continuous exposure, higher 25-hydroxyvitamin D was associated with overall mortality [HR = 0.79 (0.65–0.96) per-SD increase, Ptrend = 0.02] and colorectal cancer–specific mortality [HR = 0.83 (0.64–1.08), Ptrend = 0.16]. 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 with those with deficiency, participants with sufficient 25-hydroxyvitamin D had lower overall mortality after multivariable adjustment [HR: 0.61 (0.37–1.01)].
Prediagnosis 25-hydroxyvitamin D is inversely associated with overall and colorectal cancer–specific mortality among Black Americans with colorectal cancer. Correcting vitamin D deficiency may improve survival of these patients, particularly for obese individuals and smokers.
Our results support including more Black Americans in trials of vitamin D supplementations to improve colorectal cancer outcomes.
