Familial transitional cell carcinoma among the population of Iceland

Purpose: Several case reports have described familial aggregation of transitional cell carcinoma of the urinary tract but to our knowledge only 1 epidemiological study specifically addressed the issue of familial bladder cancer. We evaluated the extent of familial aggregation of transitional cell carcinoma among the population of Iceland. Materials and Methods: The first to third degree relatives of 190 patients with bladder, ureter or renal pelvis transitional cell carcinoma diagnosed between 1983 and 1992 in Iceland were identified through the Icelandic Cancer Family Resource. The records of these 12,328 relatives were subsequently linked to the 1965 to 1994 cancer registry. The observed occurrence of transitional cell carcinoma of the urinary tract was compared to the expected occurrence based on age, gender and calendar specific incidence rates. Observed-to-expected ratios and 95% confidence intervals were calculated. Results: In 41 of the 190 pedigrees at least 1 relative had transitional cell carcinoma of the urinary tract. Of the probands 38 had only 1 and 3 had 2 affected relatives. The prevalence of family history of transitional cell carcinoma was 3% in first degree and 10% in first or second degree relatives. The risk of transitional cell carcinoma among all relatives was slightly elevated (observed-to-expected ratio 1.24, 95% confidence interval 0.90 to 1.67). The observed-to-expected ratio was greater among second and third degree relatives than among first degree relatives. Conclusions: The risk of transitional cell carcinoma among relatives of patients is somewhat increased. However, the greater risk for more distant relatives argues against the existence of a hereditary subtype of bladder transitional cell carcinoma, at least in the founder population of Iceland.