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 nonbladder 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 ORs, with corresponding 95% confidence intervals (CI), 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 nonurologic 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.
This study found a positive association between family history and bladder cancer in first- and second-degree relatives, with an added effect attributed to smoking. Given the detriments of bladder cancer, at-risk individuals should receive family history screening and tobacco cessation and avoidance counseling.