Cancer incidence in relatives of patients with testicular cancer in the eastern part of The Netherlands.

OBJECTIVES: To investigate the incidence of malignant tumors in first-degree relatives of patients with testicular cancer. METHODS: Information about the occurrence of cancer in relatives of patients treated for testicular germ cell cancer (TC) at the Department of Urology of the University Medical Centre Nijmegen from 1986 to 1997 was collected using postal questionnaires from 379 (72%) of 524 patients. The expected numbers of cancers in relatives were computed from age- and sex-specific incidence data in the Netherlands Cancer Registry. The observed/expected (O/E) ratios with 95% confidence intervals (CIs) were calculated using Byar's approximation of the exact Poisson test. RESULTS: The O/E ratio for developing cancer in the families of patients with TC was 1.2 (95% CI 1.0 to 1.3). Among first-degree relatives of patients with TC, more TC was observed than expected (O/E 3.3; 95% CI 1.4 to 6.9). The risk for brothers of patients with TC increased 5.9-fold (95% CI 2.2 to 12.8). Both the risk of developing lung cancer (O/E 1.5) and malignancy of the female genital tract in sisters (O/E 2.8) was slightly increased. In contrast, the risk of urinary tract malignancies (O/E 0.3) and other and unknown primary tumors (O/E 0.2) had a lower incidence among relatives. However, both the increased and decreased risk of nontesticular cancer for first-degree relatives may have been caused by misclassification. CONCLUSIONS: TC clusters in families were more pronounced among brothers than among fathers and sons. This study supports previous reports that families of patients with TC do not seem to be prone to nontesticular cancer. Additional investigations in families with TC are recommended to map candidate genes for TC