Familial bladder cancer in the national Swedish family cancer database

Purpose: We analyzed the risk of bladder cancer in offspring according to p arental and sibling cancer using the national Swedish Family Cancer Databas e. Materials and Methods: Cancer data were obtained from the Swedish Cancer Re gistry for 1958 to 1996, including 2,105 cases of bladder cancer in offspri ng. The standardized incidence ratio was used to measure cancer risk in off spring according to familial cancer status. Results: The incidence ratio of bladder cancer increased in Sweden from 195 8 to 1996 and it was 3 to 4-fold higher in males than in females. We identi fied 65 families in which the parents and offspring had bladder cancer with a familial risk of 1.35 (95% confidence interval [CI] 0.97 to 1.79) in son s and 2.29 (95% CI 1.46 to 3.29) in daughters. Discordant cancer sites asso ciated with bladder cancer in the 2 generations were the kidney and thyroid with a standardized incidence ratio of 1.58 (95% CI 1.18 to 2.05) and 1.89 (95% CI 1.00 to 3.05), respectively. Sibling risk was higher compared with offspring risk with a standardized incidence ratio of 2.96 (95% CI 1.41 to 5.08) and in males there was a statistically significant ratio of sibling- to-offspring risk of 2.66 (95% CI 1.29 to 5.45). Patient age at onset modif ied the familial risk. The highest familial risk of 7.26 (95% CI 2.61 to 14 .24) was observed in the brothers of bladder cancer probands diagnosed befo re age 45 years. Conclusions: The relatively high ratio of sibling-to-offspring risk as well as observed gender specific effects in bladder cancer may reflect an X lin ked susceptibility gene.