• John P Pierce, Ruth E Patterson, Carolyn M Senger, Shirley W Flatt, Bette J Caan, Loki Natarajan, Sarah J Nechuta, Elizabeth M Poole, Xiao-Ou Shu, and Wendy Y Chen.
• Affiliations of authors: Cancer Prevention and Control Program, Moores UCSD Cancer Center, University of California-San Diego, La Jolla, CA (JPP, REP, CMS, SWF, LN); Division of Research, Kaiser Permanente, Oakland, CA (BJC); Division of Epidemiology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN (SJN, X-OS); Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (EMP, WYC); Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA (WYC).
• J. Natl. Cancer Inst. 2014 Jan 1; 106 (1): djt359.

BackgroundThere is controversy on whether former smokers have increased risk for breast cancer recurrence or all-cause mortality, regardless of how much they smoked.MethodsData were from three US cohorts in the After Breast Cancer Pooling Project, with detailed information on smoking among 9975 breast cancer survivors. Smoking was assessed an average of 2 years after diagnosis. Delayed entry Cox proportional hazards models were used to examine the relationships of smoking status, cigarettes per day, years of smoking, and pack years with breast cancer prognosis. Endpoints included breast cancer recurrence (n = 1727), breast cancer mortality (n = 1059), and overall mortality (n = 1803).ResultsCompared with never smokers, former smokers with less than 20 pack-years of exposure had no increased risk of any outcome. However, former smokers with 20 to less than 34.9 pack-years of exposure had a 22% increased risk of breast cancer recurrence (hazard ratio [HR] = 1.22; 95% confidence interval [CI] = 1.01 to 1.48) and a 26% increased risk of all-cause mortality (HR = 1.26; 95% CI = 1.07 to 1.48). For former smokers with 35 or more pack-years of exposure, the probability of recurrence increased by 37% (HR = 1.37; 95% CI = 1.13 to 1.66), breast cancer mortality increased by 54% (HR = 1.54; 95% CI = 1.24 to 1.91), and all-cause mortality increased by 68% (HR = 1.68; 95% CI = 1.44 to 1.96). Current smoking increased the probability of recurrence by 41% (HR = 1.41; 95% CI = 1.16 to 1.71), increased breast cancer mortality by 60% (HR = 1.61; 95% CI = 1.28 to 2.03), and doubled the risk of all-cause mortality (HR = 2.17; 95% CI = 1.85 to 2.54).ConclusionsLifetime cigarette smoking was statistically significantly associated with a poor prognosis among women diagnosed with breast cancer, dose-dependent increased risks of recurrence, and breast cancer and all-cause mortality.

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