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-α) on the rate of increase in BCC numbers after first presentation. Individually, male gender, skin type 1, CYP2D6 EM, VDR TT and TNF-α 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.