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

Young women who smoke and have been smoking a pack a day for a decade or more have a significantly increased risk of developing the most common type of breast cancer. That is the finding of an analysis published early online in Cancer, a peer-reviewed journal of the American Cancer Society. The study indicates that an increased risk of breast cancer may be another health risk incurred by young women who smoke.

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; however, few studies have evaluated risks according to different subtypes of breast cancer.

To investigate, Christopher Li, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, and his colleagues conducted a population-based study consisting of 778 patients with estrogen receptor positive breast cancer and 182 patients with triple-negative breast cancer. Estrogen receptor positive breast cancer is the most common subtype of breast cancer, while triple-negative breast cancer 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 estrogen receptor positive breast cancer. In contrast, smoking was not related to a woman's risk of triple-negative breast cancer.

"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," said Dr. Li.