Interaction between blood pressure and genetic risk score for bladder cancer, and risk of urothelial carcinoma in men

There is substantial genetic predisposition to bladder cancer (BC). Recently, blood pressure (BP) was positively associated with BC risk in men, but the potential interaction with genetic susceptibility for BC is unknown. We investigated a weighted genetic risk score (wGRS) of 18 BC genetic variants, BP, and their interaction, in relation to incident urothelial cancer (UC, n = 385) risk in 10,576 men. We used Cox regression, the likelihood ratio test, and the relative excess risk for interaction to calculate hazard ratios (HR) of UC, multiplicative interaction and additive interaction respectively. There was evidence of a positive additive interaction between SBP and the wGRS in relation to aggressive (P = 0.02) but not non-aggressive (P = 0.60) UC. The HR of aggressive UC was for SBP ≥ 140 mmHg and the upper 50% of the wGRS combined 1.72 (95% CI 1.03–2.87) compared to the counterpart group. Additionally, the 20-year risk of aggressive UC in 60 year-old men was 0.78% in the low SBP/low wGRS group and 1.33% in the high SBP/high wGRS group. Our findings support a potential additive interaction between the wGRS and SBP on aggressive UC among men. If replicated, the findings on interaction may provide biological and public health insight to prevent aggressive UC.