Incidence of metachronous testicular cancer in patients with extragonadal germ cell tumors.

BACKGROUND: The frequency of subsequent testicular cancer (referred to as metachronous testicular cancer) in men who have had previous testicular cancer is relatively high. The rate of metachronous testicular cancer in men with extragonadal germ cell tumors (EGCTs), however, is largely unknown. We conducted a retrospective study of EGCT patients to determine the incidence, cumulative risk, and specific risk factors for metachronous testicular cancers. METHODS: A standardized questionnaire about patient characteristics, the extent of EGCT disease, any second malignancies, and treatments received was completed for 635 patients with EGCTs identified from the medical records of 11 cancer centers in Europe and the United States from 1975 through 1996. Comparisons with age group-specific data from the Saarland, Germany, population-based cancer registry were used to calculate the standardized incidence ratio (SIR). The Kaplan-Meier method was used to analyze survival data and cumulative risk. All statistical tests were two-sided. RESULTS: Sixteen EGCT patients (4.1%) developed metachronous testicular cancers, with a median time between diagnoses of 60 months (range, 14-102 months). The risk of developing metachronous testicular cancers was statistically significantly increased in patients with EGCTs (observed = 16; expected = 0.26; SIR = 62; 95% confidence interval [CI] = 36 to 99) and in subsets of EGCT patients with mediastinal location (SIR = 31; 95% CI = 8 to 59), retroperitoneal location (SIR = 100; 95% CI = 54 to 172), and nonseminomatous histology (SIR = 75; 95% CI = 43 to 123). The cumulative risk of developing a metachronous testicular cancer 10 years after a diagnosis of EGCT was 10.3% (95% CI = 4.9% to 15.6%) and was higher among patients with nonseminomatous EGCTs (14.3%; 95% CI = 6.7% to 21.9%) and retroperitoneal EGCTs (14.2%; 95% CI = 5.6% to 22.8%) than among patients with seminomatous EGCTs (1.4%; 95% CI = 0.0% to 4.2%) and mediastinal EGCTs (6.2%; 95% CI = 0.1% to 12.2%). CONCLUSIONS: Patients with EGCTs, particularly those with retroperitoneal or nonseminomatous tumors, but also those with primary mediastinal EGCTs, are at an increased risk of metachronous testicular cancer.