Family history and risk of bladder cancer: an analysis accounting for first- and second-degree relatives

Although evidence suggests that a positive family history of bladder cancer in first-degree relatives is an important risk factor for bladder cancer occurrence, results remain unclear. The influence of family history of non-bladder cancers and more distant relatives on bladder cancer risk is inconsistent. This research therefore, aims to increase the understanding of the association between family history and bladder cancer risk based on worldwide case-control studies. In total 4,327 cases and 8,948 non-cases were included. Pooled odds ratios (ORs), with corresponding 95% confidence intervals (CIs), were obtained using multilevel logistic regression models, adjusted by age, sex, ethnicity, smoking status, and smoking pack-years. The results show bladder cancer risk increased by having a first- or second-degree relative affected with bladder cancer (OR 2.72, 95%CI 1.55-4.77 and OR 1.71, 95%CI 1.22-2.40, respectively), and non-urologic cancers (OR 1.61, 95%CI 1.19-2.18). Moreover, bladder cancer risk increased by number of cancers affected first-degree relatives (for 1 and >1 first-degree relatives: OR 1.42, 95% CI 1.02-2.04; OR 2.67, 95% CI 1.84-3.86, respectively). Our findings highlight an increased bladder cancer risk for a positive bladder cancer family history in first- and second-degree relatives, and indicate a possible greater effect for an increment of numbers of affected relatives.