Trends in testicular germ cell cancer incidence in Australia

Although increasing incidence of testicular germ cell cancer has been reported in many developed nations, national estimates for Australia, with histological differentiation, are not currently available. Using data from all state and territory population-based cancer registries in Australia, this paper reports on incidence trends for seminomas and non-seminomas in Australia between 1982 and 2004 using Joinpoint and Age-Period-Cohort models. Of the 10,528 testicular germ cell cancers diagnosed during this period, 6086 (58%) were seminomas. Incidence rates have increased (2.6% per year) in Australia since 1982, with the effect stronger among seminomas (3.4% per year) rather than non-seminomas (1.4% per year). There was a strong age effect evident for both subtypes, peaking in the 25-29 year age group for non-seminomas and the 30-34 year age group for seminomas. Non-seminoma rates reflected a significant birth cohort effect, following a U-shaped pattern with the lowest risk among the 1,945 birth cohort. The differential trends observed for Australia for seminomas and non-seminomas are consistent with those reported for the United States, but slightly different to those reported for Europe. The trends may be at least partly due to changes over time in the prevalence of etiologic or protective factors around the time of birth.