The Women's Health Resource. On the web since 1997.

Researchers Link Smoking With the Spread of Breast Cancer to the Lungs (dateline June 19, 2001)

While the association between smoking and breast cancer remains controversial, a new study suggests that smoking could increase the risk that breast cancer will spread to the lungs (called lung metastases). In a study of 261 women with breast cancer, the researchers found that the women who smoked were more likely to experience lung metastases than women who did not smoke. While further research is needed to better understand the relationship between breast cancer and smoking, this study is consistent with other data that show that smoking increases the risk of death from breast cancer.

In the study, Susan Murin, MD, FCCP and John Inciardi, PharmD, MS of the University of California-Davis Medical Center identified 87 women with breast cancer that had spread to their lungs. Each of these patients were matched with two patients who had similar breast cancer characteristics (in terms of age at diagnosis, tumor size, etc.), but whose breast cancer had not spread to the lungs.

The results of the study were as follows:

  • 38% of patients who smoked (ever) experienced the spread of breast cancer to the lungs versus 29% of patients who never smoked.
  • 24.1% of patients who actively smoked at the time of their breast cancer diagnosis experienced the spread of breast cancer to the lungs versus 15.3% who did not smoke.

These results led Dr. Murin and Inciardi to conclude that there appears to be an association between cigarette smoking and the development of lung metastases (cancer that has spread to the lungs) in women with breast cancer. While smoking has not typically been associated with a higher risk of developing breast cancer, this study confirms previous study results that have linked smoking to a higher risk of dying from breast cancer. In general, the chances of surviving breast cancer drop significantly if the cancer has spread past the breast and underarm lymph nodes to invade other body organs.

However, the researchers warn that there may be other factors that explain why the smokers in their study were more likely to have their breast cancer spread to the lungs than the non-smokers. According to Dr. Murin, smokers tend to exercise less and maintain less healthy diets than non-smokers, which may influence their cancer prognosis (outcome). Therefore, more research is needed to help determine the exact relationship between breast cancer and smoking.

Experts do know that smoking can increase the risk of several diseases, including heart disease, lung cancer, and stroke. Heart disease is the number one cause of death among Americans and lung cancer is the leading cause of cancer deaths in women today. Research has also shown that smoking may interfere with the way in which the body heals from other diseases and conditions.

Established risk factors for breast cancer include:

  • Advancing age
  • Genetics
  • Family history of breast cancer
  • Early menstruation (before age 12)
  • Late menopause (after age 50)
  • Delayed childbirth (after age 30) or having no children

However, 80% of women who are diagnosed with breast cancer do not have any identifiable risk factors. Therefore, regular breast cancer screening can help detect the disease in its earliest stages when the chances of successful treatment and survival are the greatest.

Guidelines for early breast cancer detection:

  • All women between 20 and 39 years of age should practice monthly breast self-exams and have physician performed clinical breast exams at least every three years.
  • All women 40 years of age and older should have annual screening mammograms, practice monthly breast self-exams, and have yearly clinical breast exams. The clinical breast exam should be conducted close to and preferably before the scheduled mammogram.
  • Younger women with a family or personal history of breast cancer should talk to their physicians about beginning annual mammograms before age 40.

Additional Resources and References