Month of birth and testicular cancer risk in Denmark.

On the basis of 40 years of national cancer registration, the authors analyzed the distribution of birth dates of patients with testicular cancer in the Danish male population, which has a particularly high incidence of this cancer. No significant peaks were identified, except for men with embryonal carcinomas born between 1950 and 1959, for whom a significant 12-month cycle was observed. This result differs from those of earlier studies. The number of cases of embryonal carcinomas in the 1950-1959 birth cohort is small, but it is possible that an etiologic factor that varies with season was present at the time. For all testicular cancers and for the three histologic subgroups analyzed, the authors found significant 2-month cycles. The biologic relevance of a 2-month cycle is not clear. It is concluded that there is little evidence to support the hypothesis of a systematic variation in month of birth among men with testicular cancer.