Smoking linked with increased risk of most common type of breast cancer

Young women who smoked at least 10 years had a 60 percent increased risk
Dr. Chris Li
Dr. Christopher Li, Public Health Sciences Division Photo by Susie Fitzhugh

Young women – current or recent smokers who have smoked a pack a day for a decade or more – have a significantly increased risk of developing the most common type of breast cancer, according to a new study by Dr. Christopher Li and colleagues in the Cancer Epidemiology Research Group in the Public Health Sciences Division.

The study, published Feb. 10 in the journal Cancer, indicates that an increased risk of breast cancer may be another health risk incurred by young women who smoke.

Few studies have looked at smoking’s impact on risk of different subtypes of breast cancer

The majority of recent studies evaluating the relationship between smoking and breast cancer risk among young women have found that smoking is linked with an increased risk; few, however, have evaluated risks according to different subtypes of breast cancer.

To investigate, Li and colleagues conducted a population-based study consisting of 778 patients with estrogen-receptor-positive breast cancer and 182 patients with triple-negative breast cancer. ER-positive breast cancer is the most common subtype of the disease, while triple-negative is less common but tends to be more aggressive. Patients in the study were 20 to 44 years old and were diagnosed from 2004-2010 in the Seattle-Puget Sound metropolitan area. The study also included 938 cancer-free controls.

The researchers found that young women who were current or recent smokers and had been smoking a pack a day for at least 10 years had a 60 percent increased risk of ER-positive breast cancer. In contrast, smoking was not related to a woman’s risk of triple-negative breast cancer.

Study adds to our knowledge of smoking and breast cancer link

“The health hazards associated with smoking are numerous and well known. This study adds to our knowledge in suggesting that with respect to breast cancer, smoking may increase the risk of the most common molecular subtype of breast cancer but not influence risk of one of the rarer, more aggressive subtypes,” Li said.

Postdoctoral research fellow Dr. Masaki Kawai was the paper’s first author; other co-authors from the Hutch included Dr. Kathi Malone and statistician Mei-Tzu Tang. The National Cancer Institute and the Department of Defense Breast Cancer Research Program funded the study, which also received support from Banyu Life Science Foundation International.

Adapted from a Cancer news release

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