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MONDAY, Feb. 9, 2009 (Health.com) — Do men who frequently smoke pot have a higher risk of testicular cancer than those who do not? It’s possible, according to a new study. However, the researchers say the link is currently a “hypothesis” that needs further testing.

Testicular cancer is relatively rare—a man’s lifetime chance of developing the disease is about 1 in 300 (and dying of it is about 1 in 5,000). But frequent or long-term marijuana smokers could have about double the risk of nonusers, according to the report in the Feb. 9 issue of the journal Cancer.

In the study, a team led by Janet R. Daling, MD, of the Fred Hutchinson Cancer Research Center in Seattle, interviewed 369 men between the ages of 18 and 44 from the Seattle–Puget Sound area who had been diagnosed with testicular cancer. They compared those men to 979 men who lived in the same area but did not have cancer.

Overall, 26% of the testicular cancer patients were pot smokers (15% who used daily or weekly) at the time of diagnosis, compared with 20% of men without cancer (10% who used daily or weekly).

Marijuana users had 2.3 times the risk of a type of testicular cancer known as a nonseminoma as those who were not. Testicular cancer is divided into two types, pure seminomas (60% of cases) and nonseminomas (40% of cases). The link was much weaker in men with seminomas.

These types of studies have one important caveat, however: Cancer patients may be more likely to remember—or may be more honest about—past drug use than men in the general population.

Next: Testicular cancer rates are on the rise