Does Marijuana Lead To Testicular Cancer?

By Margarita Nahapetyan

It is quite possible, according to a new report in the February 9 issue of the journal Cancer. For the first time, researchers have linked frequent marijuana use to an increased risk of testicular cancer.

The researchers, led by Dr. Janet R. Daling, Ph.D., an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, Washington, studied 369 men between the ages of 18 and 44 from the Seattle-Puget Sound area, and who had been diagnosed with testicular cancer. They compared these men with 979 men who lived in the same area, but had never been diagnosed with testicular cancer. Study participants were also asked questions about other habits that could be correlated with marijuana use, such as smoking and alcohol intake.

The results showed that regular marijuana smokers doubled their chances of developing the disease, compared with those men who never smoked it. Overall, twenty six per cent of the testicular patient group were found to be pot smokers (15 per cent smoked on a daily or weekly basis), compared with twenty per cent of men from the non-cancer group (10 per cent who smoked on a daily or weekly basis). Researches found also that marijuana users had more than 2 times the risk of a type of testicular cancer known as a nonseminoma, a fast-growing testicular malignancy that tends to affect young men, between the ages of 20 and 35, and accounts for about 40 per cent of all testicular-cancer cases.

For the past few decades, the incidence of the two main types of testicular cancer, nonseminoma and seminoma (the more common, slower growing kind that strikes men after their 30s) has increased by 3 to 6 per cent per year in the United States, Canada, Europe, Australia and New Zealand. During the same period of time, marijuana use has also risen, which led the scientists to initiate their research.

"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.

Known risk factors for testicular cancer include a family history of the disease, undescended testes and abnormal testicular development. The researchers believe that the disease begins in the womb, when some fetal germ cells fail to develop in a proper way and become vulnerable to malignancy. Later, during adolescence and adulthood, their exposure to male sex hormones causes them to become cancerous. "Just as the changing hormonal environment of adolescence and adulthood can trigger undifferentiated fetal germ cells to become cancerous, it has been suggested that puberty is a 'window of opportunity' during which lifestyle or environmental factors also can increase the risk of testicular cancer," said Daling,. "This is consistent with the study's findings that the elevated risk of nonseminoma-type testicular cancer in particular was associated with marijuana use prior to age 18."

Researchers also added that constant marijuana use has multiple negative effects on the endocrine and reproductive systems, primarily decreasing the quality of sperm. Other possible effects include decreased testosterone and male impotency.

However, the researchers said that the link is currently a "hypothesis" and their results are not definitive and need more research and testing."Our study is the first inkling that marijuana use may be associated with testicular cancer, and we still have a lot of unanswered questions," they said, "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."

In their upcoming studies the scientists plan to measure the expression of cannabinoid receptors in both seminomatous and nonseminomatous tumor tissue from the cases in the study, and to establish whether gene variation for the receptors and other molecules involved in cannabinoid signaling have their influence on the risk of testicular cancer.

Meanwhile, before any final conclusions have been made, Stephen Schwartz gave his warning to pot users, "What young men should know is that first, we know very little about the long-term health consequences of marijuana smoking, especially heavy marijuana smoking; and second, our study provides some evidence that testicular cancer could be one adverse consequence," he said. "So, in the absence of more certain information, a decision to smoke marijuana recreationally means that one is taking a chance on one's future health."

This study was supported by The National Cancer Institute, the National Institute on Drug Abuse and funds from the Hutchinson Center. The researchers from the University of Washington, Vanderbilt University and Cincinnati Children's Research Foundation were also involved in the research.