Older women who quit smoking greatly reduce bladder cancer risk

Smoking’s strong impact on bladder cancer risk among men and women is clear, but a new study shows quitting smoking can greatly reduce risk of the cancer among menopausal women.

Researchers analyzed data on 143,279 postmenopausal women from the Women’s Health Initiative study and found former smokers who quit within the last 10 years were 25% less likely to be diagnosed with bladder cancer compared to current smokers. Women’s bladder cancer risk continued to fall with greater years since quitting but remained higher than the risk among never smokers even 30 or more years after quitting, according to the data, which were published in Cancer Prevention Research (2019; 12:305-14).

“The key points for urologists I think are pretty clear: Patients should be advised to not smoke, because in addition to all of the other health problems that smoking causes, bladder cancer is also a risk. And perhaps even more importantly, if patients are smoking, they can be advised to quit to reduce bladder cancer risk even if they are older-all women in this study were post-menopausal at baseline. It is not too late for older people to benefit from quitting smoking,” study author Michael Hendryx, PhD, of the Indiana University School of Public Health-Bloomington, wrote in an email to Urology Times.

Smoking is the strongest established risk factor for bladder cancer, accounting for about 65% of disease risk in men and 20% to 30% in women. But inconsistencies remain in the literature about the dose-response relationship between years after quitting and bladder cancer risk. Data looking at smoking’s association with bladder cancer risk among women are lacking, even though female bladder cancer patients tend to have more serious prognoses and worse outcomes than men with bladder cancer at similar stages. Research looking at bladder cancer risk among postmenopausal women, who are at higher risk for bladder cancer than premenopausal women, is especially sparse, according to the study.

The authors not only investigated the dose-response relationship between years since quitting smoking and bladder cancer risk among postmenopausal women, but also looked at whether the associations differed between transitional and papillary bladder cancer subtypes.

They identified 870 cases of bladder cancer as of Feb. 28, 2017 and found, in general, that quitting lowered bladder cancer risk compared to continuing to smoke.

Continue to the next page for more.The authors found that when they adjusted for age only, former smokers were at 2.01 times higher risk and current smokers at 3.39 times the risk of bladder cancer compared to never smokers. They didn’t find a significant risk difference between never smokers and former smokers who had quit smoking for 30 years or longer. However, when the authors adjusted for number of cigarettes a day or pack-years of smoking, former smokers were in fact at significantly higher risk of bladder cancer than never smokers, even if they had quit more than three decades prior.

“This change in results suggests that smoking intensity and duration should be taken into account when analyzing the smoking-bladder cancer association,” the authors wrote.

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In time-updated models that reflected those who stopped smoking during the study period, the authors found that compared with women who continued to smoke, those who quit smoking during the follow-up years had a 39% decrease in bladder cancer risk, and the risk continued to decline over time, according to an American Association for Cancer Research press release on the study.

Findings followed similar patterns when researchers looked at the association between smoking cessation and bladder cancer subtypes. Former smokers who quit for 30 years or more had elevated risk of risk for both bladder cancer subtypes.

Among the study’s limitations, smoking prevalence in the U.S. population is 15.1% compared to smoking prevalence in the Women’s Health Initiative study, which is 6.9%. The difference might diminish the generalizability of the study’s findings, the authors wrote.