Association of Marijuana Use and the Incidence of Testicular Germ Cell Tumors

BACKGROUND: The incidence of testicular germ cell tumors (TGCTs) has been increasing the past 4 to 6 decades; however, exposures that account for this rise have not been identified. Marijuana use also grew during the same period, and it has been established that chronic marijuana use produces adverse effects on the human endocrine and reproductive systems. In this study, the authors tested the hypothesis that marijuana use is a risk factor for TGCT. METHODS: A population-based, case-control study of 369 men ages 18 to 44 years who were diagnosed with TGCT from January 1999 through January 2006 was conducted in King, Pierce and Snohomish Counties in Washington State. The responses of these men to questions on their lifetime marijuana use were compared with the responses of 979 age-matched controls who resided in the same 3 counties during the case diagnosis period. RESULTS: Men with a TGCT were more likely to be current marijuana smokers at the reference date compared with controls (odds ratio [OR], 1.7; 95% confidence interval [95% CI], 1.1-2.5). In analyses according to histologic type, most of the association between current marijuana use and TGCT was observed in men who had nonseminomas/mixed histology tumors (current use: OR, 2.3: 95% CI, 1.3-4.0). Age at first use among current users (age <18 years [OR, 2.8] vs age >= 18 years [OR, 1.3]) and frequency of use (daily or weekly [OR, 3.0] vs less than once per week [OR, 1.8]) appeared to modify the risk. CONCLUSIONS: An association was observed between marijuana use and the occurrence of nonseminoma TGCTs. Additional studies of TGCTs will be needed to test this hypothesis, including molecular analyses of cannabinoid receptors and endocannabinoid signaling, which may provide clues regarding the biologic mechanisms of TGCTs. Cancer 2009;115:1215-23. (C) 2009 American Cancer Society.