The risk of death from breast cancer was 33% lower for survivors of breast cancer who quit smoking after their diagnosis than for those who continued to smoke. These study findings were published in the Journal of Clinical Oncology.1 Mortality from breast cancer and several other causes was associated with smoking before or after diagnosis of breast cancer.

This large study involved over 20,600 women with breast cancer. It sought to evaluate how smoking status before and after a diagnosis of breast cancer was associated with mortality. It was the first study to assess smoking habits both before and after diagnosis.

“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 University of California, San Francisco School of Medicine. “About 1 in 10 breast cancer survivors smoke after their diagnosis. For them, these results should provide additional motivation to quit.”

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This observational study used data from the Collaborative Breast Cancer Study, which is conducted by the University of Wisconsin, Dartmouth College, and Harvard University. The study included women aged 20 to 79 years who were diagnosed with localized or invasive breast cancer between 1988 and 2008.

The study followed its participants for an average of 12 years after diagnosis. It compared 4 groups: women who never smoked, women who smoke and quit before diagnosis, women who smoked and quit after diagnosis, and women who continued to smoke after diagnosis.

By 2010, a total of 6778 women died, and their leading causes of death were breast cancer and cardiovascular disease.

When active smokers were compared with women who had never smoked, active smokers were more likely to die of breast cancer, respiratory cancer, other respiratory disease, or cardiovascular disease. Long-term smokers had the highest risk of death as a result of breast cancer, along with people who smoked heavily and former smokers who had quit less than 5 years before breast cancer diagnosis.

About 10% of patients with breast cancer kept smoking after their diagnosis, and these patients were more likely than nonsmokers or former smokers to die of breast cancer. Patients who quit smoking after diagnosis had lower mortality from breast cancer and respiratory cancer.

“Smoking cessation programs should be considered part of cancer therapy,” Dr 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 research team noted that the study did not assess for exposure to second-hand smoke nor did it include hormone receptor status of breast tumors.


1. 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. doi: 10.1200/JCO.2015.63.9328.