Outcome in prostate cancer: Associations with skin type and polymorphism in pigmentation-related genes

Abstract

Epidemiological studies have suggested that UV exerts a protective effect on prostate cancer. Accordingly, we determined, in 210 prostate cancer cases, whether parameters of exposure, skin type and polymorphism in MC1R, VDR and TYR were associated with the outcome parameters, histological grade, clinical stage and presence of bone metastases. We used logistic regression analysis, with correction for age and metastases, stage and grade in the models, to determine if the frequencies of individual factors were different in the patient groups. The development of metastases was not associated with UV exposure parameters. Paradoxically, patients with skin type 1 were at significantly reduced risk [P = 0.027, odds ratio (OR) 0.17, 95% CI 0.03-0.82] of developing metastases compared with cases with skin type 4. MC1R Val92/Val92 and VDR ff were associated with increased risk of metastases (ORs 4.30 and 4.98, respectively). Further, cumulative exposure (P = 0.005, OR 0.85/year) and increasing proportion of outdoor occupation (P = 0.001, OR 0.84/unit) were associated with reduced risk of advanced stage tumours. Skin types, MC1R or VDR genotypes were not significantly associated with advanced stage. None of the exposure parameters, skin types or genotypes were associated with tumour grade. While MC1R Val92/Val92 and VDR ff were only associated with bone metastases, TYR genotypes were associated with each of the outcome parameters. Thus, in logistic regression models that included age, but not advanced stage and high grade histology, TYR A1A2 was significantly associated with reduced risk of metastases (P = 0.033, OR 0.41). Similarly, in models that included age but not the other outcome parameters, associations between TYR A2A2 and high-grade and advanced stage were significant (P = 0.040, OR 0.41) or approached significance (P = 0.052, OR 0.044), respectively. These data indicate for the first time that pigmentation response to UV is associated with outcome in prostate cancer.