A study from the Fred Hutchinson Cancer Center shows that smoking among young women may increase the risk of developing estrogen receptor (ER)-positive breast cancer, but not triple negative breast cancer (TNBC).

The group led by Dr. Christopher Li conducted a population-based study among women from 22 to 44 years old diagnosed with breast cancer between January 2004 and June 2010 in the . The patients were 938 women in the control group, 778 in the ER-positive group, and 182 in the TNBC group. The researchers interviewed the patients and obtained detailed information about different aspects of their lifestyle—reproductive history, demographics, physical activity, alcohol drinking, medical history—and smoking habits—regency, number of cigarettes smoked per day, ages when smoked. The patients were divided in never smokers and ever smokers (current or former). The ever-smoker group was further categorized based on the number of pack of cigarettes smoked per year.

Smokers had increased risk of developing breast cancer overall (30%), without any significative change when the total number of years of smoking or the age women first started were considered. Although the small number of TNBC cases, the risk was associated with ER-positive breast cancer and not with TNBC. However, among current smokers, women who had been smoking for more than fifteen years had 50% increased risk of developing ER-positive breast cancer compared with women who had been smoking for fewer years. Of note is that, in women who had not been smoking for more than ten years the risk of developing ER-positive breast cancer decreased dramatically.

Various studies have correlated smoking to the risk of breast cancer, but this is one of the few studies linking smoking to ER-positive breast cancers in premenopausal women. Metabolites of tobacco, found in the breast fluid and breast tissue of current smokers, have been shown to have an estrogenic effect in in vitro studies, thus explaining the increased risk of ER-positive breast cancer in young women found in this research.

Smoking has several adverse effects and has been associated to different cancers. This is not only a study that supports previous reports linking smoking to breast cancer, but this study links smoking to a specific subtype of breast cancer (ER-positive) in young women.

 

Masaaki Kawai, Kathleen E. Malone, Mei-Tzu C. Tang, Christopher I. Li. Height, body mass index (BMI), BMI change, and the risk of estrogen receptor-positive, HER2-positive, and triple-negative breast cancer among women ages 20 to 44 years. Cancer, 2014