NEW YORK (Reuters Health) – New research suggests that marijuana use may increase the risk of testicular germ cell tumors (TGCTs), primarily nonseminoma types.

According to the report in the March 15th issue of Cancer, current marijuana use increased the odds of TGCTs by 70%.

A rise in TGCT rates has been seen in the last 4 to 6 decades, but the cause of the increase has been unclear, Dr. Janet R. Darling, from Fred Hutchinson Cancer Research Center, Seattle, and colleagues write. Since marijuana use increased during the same period and chronic use has been shown to harm the reproductive system, there may be an etiologic link.

To investigate, the researchers assessed marijuana use in 369 men who were diagnosed with TGCT from January 1999 to January 2006 in three counties in Washington State and compared it with that of 979 age-matched controls.

Overall, current marijuana users, compared with those who never used marijuana, had a 70% increased risk of TGCT. For nonseminoma tumors, however, current use increased the risk by 130%.

Among current marijuana users, the risks of TGCT were highest in those subjects who began use before 18 years of age and who used marijuana on at least a weekly basis.

Further studies, the authors note, are needed to verify these findings. Molecular analyses of cannabinoid receptors and related signaling may help to clarify the underlying mechanisms of TGCT development, they add.

Cancer 2009;115:1215-1223.