Risk of germ cell tumors among men with HIV/acquired immunodeficiency syndrome.

BACKGROUND Men with HIV/acquired immunodeficiency syndrome (AIDS) are reported to be at increased risk for germ cell tumors (GCT), particularly testicular seminoma. We investigated correlates of this association to improve understanding of GCTs. METHODS Testicular and extratesticular seminoma and nonseminoma cases were found by linking population-based cancer and HIV/AIDS registry data for 268,950 men who developed AIDS in 1980 to 2003. Standardized incidence ratios (SIR) with 95% confidence intervals (95% CI) were used to compare these cases with the number of cases expected in the demographically matched population. RESULTS Overall, seminoma risk (161 cases: SIR, 1.9; 95% CI, 1.6-2.2) was increased significantly with HIV/AIDS, whereas nonseminoma risk was not (56 cases: SIR, 1.3; 95% CI, 0.96-1.7). Extratesticular GCT risk also was increased (11 cases: SIR, 2.1; 95% CI, 1.1-3.7). Seminoma risk was elevated regardless of age, race, or HIV/AIDS transmission group. It was highest for disseminated disease (SIR, 4.7; 95% CI, 2.9-7.2) and within 9 months of AIDS onset (SIR, 7.6; 95% CI, 5.8-9.6), but it was unrelated to CD4 count and duration of HIV/AIDS. The excess risk of seminoma declined in more recent calendar periods, and it was no longer elevated (SIR, 1.4; 95% CI, 0.9-1.9) in the highly active antiretroviral treatment era. CONCLUSIONS Men with HIV/AIDS had an increased risk of seminoma, but this risk may have attenuated with improving anti-HIV/AIDS treatments. Although detection bias could partly explain the excess of this cancer, various lines of evidence support a causal relationship. Possible mechanisms underlying this association include impaired tumor immunosurveillance or AIDS-related testicular atrophy.