More Evidence That Breast Cancer Survivors Should Stop Smoking

Michael Passarelli, PhD

Michael Passarelli, PhD

The first study to assess smoking habits of women with breast cancer before and after diagnosis has found that those who quit smoking after their diagnosis had a 33% lower risk of dying of the disease than those who continued to smoke.

“Our study shows the consequences facing both active and former smokers with a history of breast cancer,” said first author Michael Passarelli, PhD, a cancer epidemiologist at the UCSF School of Medicine, in a statement. “About 1 in 10 breast cancer survivors smoke after their diagnosis. For them, these results should provide additional motivation to quit.”

The findings come from the Collaborative Breast Cancer Study, conducted by the University of Wisconsin, Dartmouth College, and Harvard University. This research involved more than 20,600 women between the ages of 20 and 79 who were diagnosed with localized or invasive breast cancer between 1988 and 2008. The study represents one of the largest to assess the impact of smoking habits on survival outcomes in women with a history of breast cancer.

In 2014, US Surgeon General issued a report on the health consequences of smoking suggesting that there may be a causal relationship between breast cancer and smoking. Previous studies have also speculated that the risk of developing breast cancer in smokers might depend on when they began smoking and for how long.

This observational study sought to shed more light on that hypothesis. Researchers followed participants for an average 12 years after diagnosis and quantified the long-term benefits of stopping smoking by comparing the causes of death among participants who: (1) never smoked; (2) smoked and quit before diagnosis; (3) smoked and quit after diagnosis; (4) continued to smoke after diagnosis.

The women were asked to report on such factors as whether they had smoked at least 100 cigarettes during their lifetime, their age when they started smoking, and the average number of cigarettes they smoked a day. The authors controlled for several important risk factors that could impact survival, including alcohol consumption and body mass index. By 2010, a total of 6778 women died—the leading causes of death were breast cancer and cardiovascular disease.

Active smokers a year before breast cancer diagnosis were more likely to die of breast cancer, respiratory cancer, other respiratory disease, or cardiovascular disease than women who had never smoked. The highest risks of death as a result of breast cancer were observed among long-term smokers, people who smoked heavily, or former smokers who quit fewer than 5 years before breast cancer diagnosis.

Approximately 1 in 10 patients continued to smoke following their diagnosis, and they were more likely than people who had never smoked and former smokers to die of breast cancer, the researchers said. Those who quit smoking after diagnosis had lower mortality from breast cancer and respiratory cancer.

“Smoking cessation programs should be considered part of cancer therapy,” Passarelli said. “Recent policy statements from leading research and clinical organizations are now urging oncologists to be as aggressive in getting their patients to stop smoking as they are in treating the cancer.”

The study did not assess for exposure to secondhand smoke nor did it include hormone receptor status of breast tumors.

Passarelli MN, Newcomb PA, Hampton JM, et al. Cigarette smoking before and after breast cancer diagnosis: mortality from breast cancer and smoking-related diseases [published online ahead of print January 25, 2016]. J Clin Oncol.