Heavy marijuana use linked to bladder cancer

Pot smokers could be putting themselves at risk for developing bladder cancer, according to the results of a study of middle-aged men who were seen at two Veterans Administration facilities.

Marijuana smoking “might be an even more potent stimulant” of malignancy than cigarette smoking, Dr. Martha K. Terris of the Medical College of Georgia in Augusta and her colleagues write in the medical journal Urology.

Terris and her team point out that head and neck and lung cancers have been tied to marijuana use, and there is evidence that these marijuana-associated malignancies may strike at an earlier age.

To determine if marijuana use might also be associated with bladder cancer, she and her colleagues evaluated 52 men with the disease who were all younger than 60 years, along with 104 age-matched controls.

Among the men with bladder cancer, 88.5 percent were habitual marijuana smokers, compared with 69.2 percent the controls.

The average quantity of marijuana use also was higher in the men with bladder cancer, the investigators found. The cancer group clocked up an average of 48 joint-years per patient—i.e., the individuals smoked the equivalent of 1 joints a day for 48 years, or 2 joints a day for 24 years, etc.—while the comparison group reported an average of 28.5 joint-years.

Tobacco use was also heavy among the study subjects, with more than 90 percent of the men in either group using tobacco, making it impossible to identify any link between cigarettes and cancer risk.

Marijuana could be more cancer-promoting than tobacco, the investigators note, given its longer half-life (up to 60 hours versus 12 hours) and the fact that marijuana is smoked without a filter and held longer in the lungs.

The drug also reduces bladder contractility, the researchers add, which could increase urine retention and thus greater exposure of the bladder to marijuana compounds.

They advise that younger patients with symptoms that might suggest bladder cancer, who aren’t usually considered at high risk, “should be questioned about a history of marijuana use.” If they answer positively, the researchers conclude, it might be advisable to conduct further tests.

SOURCE: Urology, January 2006.

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