Age at puberty and risk of testicular cancer: a meta-analysis

Testicular cancer is one of the most rapidly increasing tumour types but its aetiology is still largely unexplained. Cryptorchidism and familial testicular cancer, established risk factors, explain less than 10% of all cases. Among investigated post-natal factors, early puberty was suggested as a potential risk factor but the topic has been poorly investigated. We undertook a meta-analysis of the effect of age at puberty on testicular cancer risk, attempting at enhancing the homogeneity in the definition of the exposure among studies to obtain valid pooled estimates. Search strategies were conducted in PubMed on December 2011. All markers of puberty onset (age at voice change, age when started shaving and reported age at onset) were considered. We re-categorized age at puberty from all studies into a common three-level variable: younger than peers, same age as peers, older than peers. A total of 391 references were retrieved, of which 12 met the inclusion criteria. Later puberty appeared to be protective. In particular late vs. same age at start shaving gave an OR of 0.84 (95% CI: 0.75-0.95, five studies); late vs. same age at voice change gave an OR of 0.87 (95% CI: 0.75-1.01, five studies); and later age than peers at reported onset of puberty gave an OR of 0.81 (95% CI: 0.73-0.89, eight studies). Early puberty showed no effect on testicular cancer risk. This meta-analysis has found consistent evidence of a decreased risk of testicular cancer in association with later puberty, suggesting that post-natal factors may contribute to testicular cancer risk.