gms | German Medical Science

Introduction: Several descriptive epidemiological features of testicular cancer suggest that the etiologies of seminoma and nonseminoma of the testis may differ. To address this, we conducted a systematic review of case-control and cohort studies of the etiology of testicular cancer.

Methods: We conducted a detailed literature search and identified 150 eligible studies. We calculated ratios of relative risk (RR) estimates (RoRR: RR of seminoma divided by RR of nonseminoma) and corresponding 95% confidence intervals (95%CI).

Results: Overall 61 and 12 publications of case-control studies and cohort studies respectively reported stratified RR estimates by histologic group. The year of publication was positively associated with stratification by histologic subgroup. We extracted a total of 1,148 RR estimates, stratified by histologic subgroup, reflecting 631 exposures. Ratios of RR estimates were symmetrically distributed, with a peak at the reference value of one. The symmetry of the funnel plot suggests lack of publication bias. The corresponding p-value distribution was very close to the expected distribution under the null hypothesis of no histologic heterogeneity in the RR estimates.

Discussion: Our results do not provide evidence in support of the hypothesis that seminoma and nonseminoma have different etiologies or risk factors among adolescents and young men differ. To date, only descriptive epidemiologic features, such as the incidence age patterns and incidence time trends of seminoma and nonseminoma of the testis, have provided evidence suggesting different etiologies, especially among newborns, infants, and elderly men.