For Once, Tobacco's Not To Blame

Aggressive brain cancer not triggered by smoking, says study

TUESDAY, May 15 (HealthScout) -- Smoking may hurt your lungs, tighten your veins, irritate your eyes, wrinkle your skin and bother just about everyone around you, but tobacco apparently doesn't cause brain cancer, reports a new study.

While that news might help smokers breathe a little easier, it still doesn't mean that using tobacco is safe.

Researchers from the Yale University School of Medicine found no association between the use of cigarettes, cigars, pipes, snuff or chewing tobacco and an aggressive type of brain cancer known as a glioma. More than half of the 20,000 Americans diagnosed with this cancer each year will die within 18 months of finding out they have it, according to the Society for Neuroscience.

But, "a number of diseases, including lung cancer and cardiovascular diseases have been causally associated with cigarette smoking," cautions the study's author, Dr. Tongzhang Zheng, an associate professor of epidemiology and environmental health at Yale in New Haven, Conn. "Cigarette smoking is harmful to human health."

Zheng and his colleagues studied 375 glioma patients, along with 2,434 other people used as a control comparison. The patients, all from Iowa, were between 40 and 85 years old. One hundred and thirty-two of them and 1,068 of the others were either current or former smokers.

The study participants or their next-of-kin completed a questionnaire that detailed their smoking history, the type of cigarettes smoked, how often they smoked or used other types of tobacco, along with personal information such as family health history, occupation, height, weight, exercise history, diet information and a residential history.

The researchers then compared the brain cancer patients to the control group in numerous ways to see whether there was any association between tobacco use and brain cancer, including the age participants started smoking, the number of years they smoked and the number of cigarettes smoked per day.

They found no association between tobacco use and this type of brain cancer, according to the study.

Results of the study were in a recent issue of the journal Cancer Epidemiology, Biomarkers and Prevention.

Previous studies, however, have found a link between brain cancer and tobacco use in mice. Zhang says he's not sure why these results don't hold true for humans, though he suspects the human blood-brain barrier may offer some protection against the harmful compounds produced by tobacco. "It is also possible that human brain tissue may differ from other organs in susceptibility to tobacco carcinogens," he says.

"We really have a very limited understanding of the causes and prevention of brain cancers," says Dr. Michael Thun, the head of epidemiological research for the American Cancer Society. But, he says this study provides useful information by ruling out a possible cause of brain cancer, though he too cautions against assuming it's OK to continue tobacco use.

"This is one of the few cancers that smoking has not been shown to cause," says Thun. "What's really remarkable is how many cancers smoking is associated with, such as lung, mouth, throat, larynx, esophagus, pancreas, bladder, kidney and leukemia."

What To Do

To see if there are any clinical trials on brain tumors, check out Veritas Medicine.

To learn more about gliomas, go to Boston Neurosurgery or the Society for Neuroscience.

This fact sheet from the National Cancer Institute details the effects of smoking on the body. The U.S. Centers for Disease Control and Prevention and the American Cancer Society both offer tips on quitting smoking.

You might also want to read these HealthScout articles on tobacco use or brain cancer.

And if you're interested in clinical trials for brain cancer, visit Veritas Medicine.

SOURCES: Interviews with Tongzhang Zheng, M.D., associate professor, epidemiology and environmental health, Yale School of Medicine, New Haven, Conn.; Michael Thun, M.D., head, epidemiological research, American Cancer Society, Atlanta, Ga.; April 2001 Cancer Epidemiology, Biomarkers and Prevention
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