February 10, 2009
Using marijuana, either frequently or over a long time period, may significantly increase a man's risk of developing the most aggressive type of testicular cancer. That's the conclusion of researchers at Fred Hutchinson Cancer Research Center, who have published their finding in the journal Cancer.
The researchers found that being a marijuana smoker at the time of diagnosis was associated with a 70 percent increased risk of testicular cancer.
The risk was particularly elevated — about twice that of those who never smoked marijuana — for those who used marijuana at least weekly and/or who had long-term exposure to the substance beginning in adolescence.
The results also suggested that the association with marijuana use 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 cellular subtypes of testicular cancer, nonseminoma and seminoma — the more common, slower growing kind that strikes men in their 30s and 40s — has increased by 3 percent 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 accordingly, 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.
Established risk factors for testicular cancer include a family history of the disease, undescended testes and abnormal testicular development. The disease is thought to begin in the womb, when some fetal germ cells fail to develop properly and become vulnerable to malignancy. Later, during adolescence and adulthood, it is thought that exposure to male sex hormones coaxes these cells to become cancerous.
