Smokers Have Increased Risk of Breast Cancer Recurrence and Mortality
NEW YORK (Reuters Health) – Current smokers and former heavy smokers have a greater risk of breast cancer recurrence and mortality than women who have never smoked, according to a new study.
For the report, presented February 20 at the annual meeting of the American College of Preventive Medicine in New Orleans, Louisiana, researchers reviewed records from 9975 breast cancer survivors who were part of the After Breast Cancer Pooling Project. Delayed entry Cox proportional hazard models were used to examine the relationship between breast cancer prognosis and a woman’s smoking status, cigarettes per day, years of smoking, and pack-years.
Former smokers with 20 to 35 pack-years of exposure had a 22% increased risk of breast cancer recurrence and a 26% increased risk of all-cause mortality compared to non-smokers. Those with 35 pack-years of exposure or more had a 37% increased risk of breast cancer recurrence, a 54% increased risk of breast cancer mortality, and a 68% increased risk of all-cause mortality.
Current smokers (with a mean 39 pack-years of exposure) had a 41% higher probability of breast cancer recurrence, a 60% higher probability of breast cancer mortality, and double the risk of all-cause mortality compared to non-smokers. Former smokers with less than 20 pack-years of exposure had no increased risk of any outcome.
The findings were also published online December 7 in the Journal of the National Cancer Institute.
The authors believe this is the first study to discover a statistically significant, dose-dependent association between lifetime cigarette smoking and breast cancer recurrence and all-cause mortality. According to co-author Dr. Carolyn Senger from the University of California-San Diego in La Jolla, “These findings are especially significant given that most longitudinal studies have indicated that breast cancer survivors who smoke have increased risk of all-cause mortality while women who quit after diagnosis do not.”
Dr. Senger added, “While the latest Surgeon General report and many studies have documented the way smoking affects cardiovascular and respiratory health, which likely explains some of the impacts of smoking on mortality seen in most studies of breast cancer survivors, this new data suggests a breast cancer-specific mechanism of risk.”
She told Reuters in an email that the results emphasize the public health importance of early cessation to reduce long-term risk. “While it surprised me that the increased risk was confined to heavy smokers, for practitioners seeing breast cancer survivors, there is an important opportunity to motivate women to quit smoking before they accumulate 20 pack-years of exposure,” Dr. Senger said.
Dr. Laura Esserman, director of the Carol Franc Buck Breast Care Center at the University of California, San Francisco, agreed. “We now have data that smoking impacts breast cancer mortality. Not that we need another reason to get people to stop smoking, but here is yet another important finding that cigarette smoking leads to health problems,” she told Reuters Health. “Any newly-diagnosed breast cancer patient who smokes should be put into a program to help them quit. If it is worth treating their breast cancer, it is worth helping them quit smoking.”
J Natl Cancer Inst 2013
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