Is Smoking Associated with TNBC? Yes. Or No. Depends on Which Study You Look At

Young women who smoke and have been smoking a pack a day for a decade or more have a significantly increased risk of developing hormone-positive  breast cancer, but smoking is not related to a woman’s risk of triple-negative breast cancer, according to a new analysis published online in Cancer, a peer-reviewed journal of the American Cancer Society.

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. 

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. 

“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.

Previous research has also shown that postmenopausal women who smoke do not face an increased risk of TNBC, according to research using data from the Women's Health Initiative. The study enrolled 148,030 women, 300 of whom had TNBC and 2,479 of whom had estrogen-positive disease. Smoking and alcohol use were both associated with ER-positive breast cancer, but not with TNBC. The research was published in Cancer Causes Control (2011).* 

BUT:  An older study showed just the opposite. A 2001 study in the International Journal of Cancer found evidence that smoking—even for those who gave up the habit—was associated with an increased risk of hormone-negative breast cancer.  In this long-term study, 10,902 women, 35 percent of whom were smokers, were followed for an average of 12.4 years. Those who smoked had an increased risk of hormone-negative breast cancer, but not of hormone-positive.  Ex-smokers specifically had an increased risk of progesterone-negative breast cancer.**

THE MORAL:  Don't smoke, because you don't want any kind of cancer.

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*Kabat, Geoffrey C., Kim, Mimi, Phipps, Amanda I., Li, Christopher I., Messina, Catherine R., Wactawski-Wende, Jean, Kuller, Lewis, Simon, Michael S., Yasmeen, Shagufta, Wassertheil-Smoller, Sylvia  Rohan, Thomas E., ”Smoking and alcohol consumption in relation to risk of triple-negative breast cancer in a cohort of postmenopausal women.” Cancer Causes and Control : CCC , pp. 1-9 (2011).

** Manjer, J., Malina, J., Berglund, G., Bondeson, L., Garne, J. P.   Janzon, L., “Smokingassociated with hormone receptor negative breast cancer.” International Journal of Cancer, vol. 91, no. 4, 580-584 (2001).

Read more about TNBC and smoking in my book, Surviving Triple-Negative Breast Cancer.

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