Frequent marijuana use may significantly increase a man's risk of developing the most aggressive type of testicular cancer, according to new study by researchers at Fred Hutchinson Cancer Research Center.
The study, published in the journal Cancer, shows that being a marijuana smoker 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 their teens.
Interestingly, 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.
"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 study author Stephen M. Schwartz, an epidemiologist 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 (those that eventually make sperm in adulthood) 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.
The researchers noted that 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.
"Our study is the first inkling that marijuana use may be associated with testicular cancer, and we still have a lot of unanswered questions," Schwartz said in clonclusion, such as why marijuana appears to be associated with only one type of testicular cancer. "We need to conduct additional research to see whether the association can be observed in other populations, and whether measurement of molecular markers connected to the pathways through which marijuana could influence testicular cancer development helps clarify any association that exists," he said.
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Source: Fred Hutchinson Cancer Research Center