Cigarette smoking increases bladder cancer risk

  Women Smokers at Higher Risk for Bladder Cancer

Journal of the National Cancer Institute (Vol. 93, No. 7), but an American Cancer Society (ACS) expert on cancer risk urges caution in interpreting the study’s results.

At the University of Southern California, J. Esteban Castelao, MD, PhD, and colleagues compared tobacco use among 1,514 bladder cancer patients in the Los Angeles area and the same number of people without bladder cancer.

In both men and women, the likelihood of getting bladder cancer went up with the number of cigarettes smoked per day and the number of years of regular smoking, but at most levels of consumption, the researchers say, women were more likely to develop the disease than men.

The difference in the men’s and women’s bladder cancer risk became larger as cigarette consumption went up. Among two-pack-a-day smokers who had been puffing for 40 years, women were more than twice as likely to develop bladder cancer as men. Smoking filtered or "low-tar" cigarettes didn’t make a difference.

"Our results add one more piece of evidence to a possible higher susceptibility of women to smoking-related cancers," says Castelao, lead author of the study.

Cancer-Risk Expert Questions Conclusions

But Michael J. Thun, MD, vice-president of epidemiology and surveillance research for the American Cancer Society (ACS) says that in the U.S., women have about four times lower bladder cancer risk than men if neither smoke, and that the 1989 Surgeon General’s report estimates "just under a three-fold increase in both men and women for the risk of bladder cancer from smoking."

Thun also notes that the USC study was a case-control study, in which patients with a disease were asked about habits known to cause that disease after they had been diagnosed. That, he notes, can influence the accuracy of their memories of how much they engaged in that behavior, a well-known effect called recall bias.

However, Castelao says, the women’s blood showed higher levels of chemicals from tobacco smoke thought to cause cancer, suggesting women may be slower to detoxify such carcinogens. Lung studies have shown similar findings, he says.

The historically lower rate of bladder cancer among women may just reflect that at one time, far fewer women smoked than men, something that has changed too recently to be reflected in current -- but not future -- bladder cancer rates, according to the study.

"And other, unknown factors may play a role" in determining why men currently get bladder cancer more frequently than women, says Castelao.

High Risk Clear for Both Men and Women

Thun says controversy over which sex is more at risk can distract from a more important point.

"The main thing to remember about smoking and bladder cancer is how extraordinarily high the risks from smoking are in both men and women," he notes. "And male or female, the most certain way to reduce cancer risk for those who smoke, is to quit," he adds.

Castelao agrees that quitting is essential for those who want to reduce their risk of bladder cancer.

"Our study clearly showed that both men and women ex-smokers have a lower risk of bladder cancer than current smokers, and that the reduction in the risk is proportional to the length of time since quitting," he says.

The ACS estimates that in 2001 there will be about 54,300 new cases of bladder cancer diagnosed in the United States (about 39,200 in men and 15,100 in women), with about 12,400 deaths from the disease (about 8,300 men and 4,100 women).

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