According to the Los Angeles County Health Department, more than 1 million adults in the county smoke cigarettes. The association between lung cancer and smoking is well known; however, a new study suggests that the impact of smoking on breast cancer might be larger than previously assumed. The results of the study were presented at a May 24 press briefing, held in advance of the American Society of Clinical Oncology (ASCO) 2011 Annual Meeting this June. The study found that not only was the risk for invasive breast cancer higher in smokers than in nonsmokers but also that it increased according to years of cigarette smoking. Lead author Stephanie R. Land, PhD, explained that, compared to women who never smoked, the breast cancer risk was 34% higher for women who smoked between 15 and 35 years. The risk was 59% for women who smoked for at least 35 years; however, there was no increased risk for breast cancer for women who smoked for less than 15 years.
Dr. Land noted that this is the third large prospective study to report a strong association between smoking and breast cancer; furthermore, it is the first to show additional risk in women who are already at higher risk for the disease. A previous large study of nearly 80,000 postmenopausal women found that current smokers had a 16% increase in breast cancer risk and that former smokers had a 9% increase in risk. A second study found that current and former smokers had a 39% higher rate of dying from breast cancer than women who had never smoked. Dr. Land and colleagues found that in addition to breast cancer, long-term smokers had significantly higher risks for lung cancer and colon cancer than nonsmokers or those who had shorter smoking histories.
As part of the National Surgical Adjuvant Breast and Bowel Project’s Breast Cancer Prevention Trial, Dr. Land and colleagues analyzed the risk for invasive cancer of the breast, endometrium, lung, and colon in 11,064 women at elevated risk for breast cancer. Participants self-reported cigarette smoking, alcohol use, and physical activity. At baseline, 54% of women reported low levels of physical activity or inactivity, 45.7% reported moderate to heavy physical activity, 20.5% reported being nondrinkers, 65.8% reported consuming no more than 1 drink daily, and 13.3% reported consuming more than one drink per day. In addition, 12.8% reported current use of tobacco. A follow-up article will provide further details.
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