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Marijuana use linked to early bladder cancer

Source: January Issue Of Urology
Toni Baker Jan. 26, 2006

Smoking marijuana appears to be a risk factor for bladder cancer and may even contribute to younger people getting the disease, researchers say.

Smoking cigarettes is the major risk factor for bladder cancer, which is most common among people age 60 and older, says Dr. Martha Terris, urologist at the Medical College of Georgia and Veterans Affairs Medical Center in Augusta.

But a study of younger patients * 52 men age 44 to 60 *  with transitional cell bladder cancer at VA hospitals in Augusta and Palo Alto, Calif., showed that 88.5 percent had a history of smoking marijuana, says Dr. Terris, senior author on the study published in the January issue of Urology.

Nearly 31 percent of the cancer patients still smoked marijuana, compared to 20 percent of those in an age-matched control group.

"We noticed several younger patients who had developed transitional cell carcinoma were similar in that they all shared a history of marijuana smoking," Dr. Terris says. "The literature has suggesed that marijuana-smoking increases the risk of head and neck cancer and lung
malignancies, and that these tumors tend to develop earlier and behave more aggressively in marijuana smokers."

That prompted physicians at the VA hospitals affiliated with Stanford University Medical Center and MCG to look at marijuana use as well as exposure to other carcinogens, including tobacco, radiation, Agent Orange, smoked or processed meats and synthetic dyes used in the textile industry, in their patients. Serving as controls were 104 patients seeking urology care at the VA hospitals for reasons other than bladder cancer.

Bladder cancer patients and controls had similar rates of exposure to all the risk factors except marijuana. In fact, the study indicates smoking marijuana may be as bad or worse than cigarette smoking as a risk factor for bladder cancer.

"Marijuana-smoking might be an even more potent stimulant of malignant transformation in transitional epithelium than tobacco smoking," they write, noting that marijuana metabolites have a half-life in the urine about five times greater than nicotine metabolites. Studies of
delta-9-tetrahydrocannabinol, or THC, the main psychoactive substance in marijuana, have demonstrated both anti-tumor and tumor-promoting properties. Either way, THC hangs around a long time in the bladder and urine.

Marijuana smoke also has many of the same carcinogen-containing tars as cigarettes and may get even more into the body because marijuana cigarettes are unfiltered and users tend to hold the smoke in their lungs for prolonged periods, researchers say.

The combination of smoking cigarettes and marijuana may have an unfortunate synergy. "The differences and interactions between marijuana and tobacco use also merit further scrutiny," they write.

Also, larger-scale epidemiologic and basic science studies are needed to confirm the role of marijuana use in development of bladder cancer.

For now, when doctors find blood in a young patient's urine sample, they may want to include questions about marijuana use in their follow-up and more strongly consider bladder cancer as a cause, says Dr. Terris.

And, bladder cancer patients considering marijuana to treat chemotherapy side effects, may want to reconsider. "If they are getting chemotherapy for their bladder cancer and smoking marijuana to increase their appetite, they may be undoing the benefits of chemotherapy," she says.

She noted it is likely that, as with cigarettes, risks of marijuana-smoking diminish after patients stop but never go away. "The safest move is to never start smoking anything," she says.