Combined effects of gender, skin type and polymorphic genes on clinical phenotype: use of rate of increase in numbers of basal cell carcinomas as a model system.

Patients with a basal cell carcinomas (BCC) have an increased risk of further tumors. We studied the individual and combined impact of gender, skin type and allelic genes cytochrome P450 (CYP2D6), vitamin D receptor (VDR), tumor necrosis factor-alpha, TNF-alpha) on the rate of increase in BCC numbers after first presentation. Individually, male gender, skin type 1, CYP2D6 EM, VDR TT and TNF-alpha GG were associated with more BCC/year (rate ratio (RR) 1.20-1.36) while RR for associations of combinations of two, three and four variables were greater than in their reference categories (RR 1.32-1.90, 2.20-2.84, 3.06-5.49, respectively). The data show that different factors mediate the numbers of BCC/year in males and females and, the individual contributions of variables to risk is modest.