Pot's link to oral cancer disputed

The previous study, in 1999, led by researchers from the University of California, Los Angeles, found that marijuana users were 2.5 times more likely to develop head and neck cancer, including tumors of the larynx and throat, than nonusers.

Researchers suggested that baby boomers who began smoking marijuana during the 1960s, when the drug surged in popularity, could experience higher rates of head and neck cancers as they age.

But the latest research finds no indication of an elevated risk, said Stephen Schwartz, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle and the new study's lead author. More than three times the number of participants were included in the latest study, improving the reliability of the findings, Schwartz said.

"If people are thinking about what might be happening to them in the future because of marijuana use, oral cancer is not something you should be particularly worried about," Schwartz said.

The study, published in the June issue of Cancer Research, the journal of the American Association for Cancer Research, included 407 people with oral cancer and 615 healthy adults 18 to 65 years old from King, Pierce and Snohomish counties in Washington state, who were located using random telephone surveys.

Participants were asked to describe their marijuana use from 1985 to 1995, including how often they smoked. About 25 percent of participants in both groups said they had smoked marijuana at some point in their lives.

Dr. Mark Schubert, a dentist and professor of oral medicine at the University of Washington, said he's not surprised by the latest study's findings.

"We don't tend to associate chronic marijuana smoking with oral cancers," said Schubert, who is also affiliated with the Fred Hutchinson research center.

"As clinicians, we haven't seen that as an associated risk factor."

Marijuana use has also been linked to lung cancer, with studies indicating that marijuana smoke can cause molecular and cellular changes in lung tissue that are consistent with the early stages of cancer.

Marijuana smokers inhale more deeply and hold the smoke in their lungs longer than tobacco smokers, which may explain the high levels of tar found in marijuana users' lungs. In addition, marijuana cigarettes do not have filters.

An estimated 28,260 new cases of oral cancer will be diagnosed this year nationwide, resulting in 7,200 deaths, according to the American Cancer Society. Cigarette smoking, chewing tobacco and alcohol are all known risk factors for oral cancer, which can occur on the tongue, lips, floor of the mouth and tonsils.

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