In a recent issue of Cancer, Lacson et al reported the results of a population-based case-control study that provided evidence of an association between marijuana use and the development of nonseminomatous testicular germ cell tumors (NTGCT).1 The authors found a greater than 2-fold increased risk of NTGCT in subjects with any history of marijuana use compared with never-users, but there was no such association observed between marijuana use and the development of seminomas. These findings are consistent with at least 2 prior reports that have demonstrated an association between marijuana use and the development of NTGCT.2, 3
The authors reported that all patients in their study were asked about the year of their first marijuana use. However, the results do not make any mention of the impact of age at the time of first marijuana use on the development of NTGCT. There are several reasons why this variable is of interest and should be evaluated using the data from this study.
First, because the peak incidence of NTGCT occurs during the third decade of life, the carcinogenic insults that may be responsible for the development of these tumors are likely to occur at a fairly young age.4 Furthermore, because developing spermatogonia undergo particularly high rates of replication and differentiation during puberty, there may be a higher risk of carcinogenesis from environmental exposures during this period.5 Finally, and perhaps most convincingly, the study by Daling et al demonstrated that the risk of developing NTGCT was elevated for subjects who started using marijuana at age 18 years or younger, but it was not found to be elevated for those who started using marijuana after age 18 years.2
If these data are available to be analyzed from the current study, it would be useful to know whether the results corroborate the findings of Daling et al regarding the impact of age at the time of first marijuana use on the development of NTGCT.