The study referenced above was designed to investigate the link between smoking and survival after a diagnosis of breast cancer. The study included 22,870 women aged 20 to 79 years who were diagnosed with breast cancer during the period 1988 to 2008. Study participants lived in Wisconsin, Massachusetts, or New Hampshire. The authors assessed pre-diagnosis smoking for all of the women. Results were adjusted for age at diagnosis, BMI, alcohol consumption, family history of breast cancer, age at first birth, menopausal status, hormone replacement therapy (HRT) use, education level, stage, and mammography. The women were followed for a median of 11.3 years from diagnosis.

The analysis was designed to determine the association between death and current (i.e., smoker at time of diagnosis) and long-term (>30 years) smoking prior to diagnosis. A total of 7,807 of the women died during follow up, including 3,483 from breast cancer, 1,553 from cardiovascular disease, 415 from respiratory disease, and 328 from lung cancer. Compared to never smokers, women who were smokers at diagnosis were 20% more likely to die from breast cancer during follow up. Women with over 30 years of smoking were also 20% more likely to die from breast cancer. Not surprisingly, compared to never smoking, current smoking was also associated with sharply increased mortality from lung cancer and respiratory disease, as well as elevated rates of death from cardiovascular disease. The authors conclude that current and long-term smokers in this study population were 20% more likely to die from breast cancer than never smokers.