Marijuana smokers could be putting themselves at risk for developing bladder cancer, as smoking marijuana might be an even more potent risk factor for malignancy than cigarettes. Previous research has found that head, 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. Researchers from the Medical College of Georgia in Augusta, USA, evaluated 52 men with the disease who were all younger than 60 years, along with 104 age-matched controls, to determine if marijuana use might also be associated with bladder cancer. Among the men with bladder cancer, 89 percent were habitual marijuana smokers, compared with 69 percent of the controls. The average quantity of marijuana use also was higher in the men with bladder cancer. The cancer group clocked up an average of 48 joint-years per patient, i.e. the individuals smoked the equivalent of 1 joint 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 per patient. 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, given its longer half-life (up to 60 hours versus 12 hours for nicotine) and the fact that marijuana is smoked without a filter and held longer in the lungs. The drug also reduces bladder contractility, which could increase urine retention and thus greater exposure of the bladder to marijuana compounds. The researchers 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, it might be advisable to conduct further tests.
Urology,
February 2006