A new study published online (Feb. 9) in the journal Cancer shows that frequent and/or long-term marijuana use may significantly increase a man’s risk of developing the most aggressive type of testicular cancer. This study, from researchers at Fred Hutchinson Cancer Research Center, illustrates how marijuana smokers have as much as a 70 percent increased risk of testicular cancer. The risk is particularly elevated (about twice that of those who never smoked marijuana) for those who use marijuana at least weekly and/or who have long-term exposure to the substance beginning in adolescence.
The association might be limited to nonseminoma, a fast-growing testicular malignancy that tends to strike early, between ages 20 and 35, and accounts for about 40 percent of all testicular-cancer cases. (Since the 1950s, the incidence of the two main types of testicular cancer, nonseminoma and seminoma – has increased by 3 to 6 percent per year in the U.S., Canada, Europe, Australia and New Zealand. During the same time period, marijuana use in North America, Europe and Australia has risen at a corresponding level, which is one of several factors that led the researchers to hypothesize a potential association.
“Our study is not the first to suggest that some aspect of a man’s lifestyle or environment is a risk factor for testicular cancer, but it is the first that has looked at marijuana use,” said author Stephen M. Schwartz, M.P.H., Ph.D., an epidemiologist and member of the Public Health Sciences Division at the Hutchinson Center.
Chronic marijuana exposure has multiple adverse effects on the endocrine and reproductive systems, primarily decreased sperm quality. Other possible effects include decreased testosterone and male impotency. Because male infertility and poor semen quality also have been linked to an increased risk of testicular cancer, this further reinforced the researchers’ hypothesis that marijuana use may be a risk factor for the disease.