Predicted plasma 25-hydroxyvitamin D and risk of renal cell cancer

Abstract

Background: Although the kidney is a primary organ for vitamin D metabolism, the association between vitamin D and renal cell cancer (RCC) remains unclear.

Methods: We prospectively evaluated the association between predicted plasma 25-hydroxyvitamin D [25(OH)D] and RCC risk among 72,051 women and 46,380 men in the period from 1986 to 2008. Predicted plasma 25(OH)D scores were computed using validated regression models that included major determinants of vitamin D status (race, ultraviolet B flux, physical activity, body mass index, estimated vitamin D intake, alcohol consumption, and postmenopausal hormone use in women). Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards models. All statistical tests were two-sided.

Results: During 22 years of follow-up, we documented 201 cases of incident RCC in women and 207 cases in men. The multivariable hazard ratios between extreme quintiles of predicted 25(OH)D score were 0.50 (95% CI = 0.32 to 0.80) in women, 0.59 (95% CI = 0.37 to 0.94) in men, and 0.54 (95% CI = 0.39 to 0.75; P trend < .001) in the pooled cohorts. An increment of 10 ng/mL in predicted 25(OH)D score was associated with a 44% lower incidence of RCC (pooled HR = 0.56, 95% CI = 0.42 to 0.74). We found no statistically significant association between vitamin D intake estimated from food-frequency questionnaires and RCC incidence.

Conclusion: Higher predicted plasma 25(OH)D levels were associated with a statistically significantly lower risk of RCC in men and women. Our findings need to be confirmed by other prospective studies using valid markers of long-term vitamin D status.

Figure 1.

Pooled multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) of renal cell cancer for a 10ng/mL increment in predicted plasma 25-hydroxyvitamin D score across strata of various factors. Multivariable hazard ratios were adjusted for age (y), smoking status (never, past, current), history of hypertension, history of diabetes, body mass index (BMI; kg/m², continuous), and parity (in women: 0, 1–2, 3, 4, ≥5 children) except for the stratified variable. The pooled hazard ratios were calculated by combining the multivariable hazard ratios from each cohort with meta-analytic methods using random effects model. All statistical tests were two-sided.