Breast cancer is the most common cancer, and the second leading cause of cancer death among women. Despite treatment advances, the overall recurrence rate for breast cancer is disappointingly high. One common form of relapse is distant metastases that most often occur in the lung, bone, liver, and brain. The risk of developing metastases is multifactorial, and much of this risk remains unexplained. Results of epidemiologic studies indicate that smokers who develop breast cancer have a higher mortality rate than non-smokers. Murin and Inciardi studied the possible association between cigarette smoking and the development of pulmonary metastatic disease in women with breast cancer.

The case-control study involved 87 women with unilateral, invasive breast cancer and pulmonary metastatic disease. Each patient was matched with two control patients who did not have pulmonary metastases. The patients were matched for year of diagnosis, age at diagnosis, size of primary tumor, and nodal status. Analysis was performed to determine the odds of smoking among women with pulmonary metastases compared with the matched control patients after correction for confounding variables.

A higher percentage of patients in the group with pulmonary metastases were classified as ever-smokers than those without pulmonary disease. About 24 percent of patients with pulmonary metastases were actively smoking at the time of diagnosis compared with about 15 percent of the patients in the control group. The odds ratio for active smoking among women with pulmonary metastases was 1.96.

The authors conclude that there appears to be an association between cigarette smoking and the development of pulmonary metastases in women with breast cancer. This relationship may explain the higher mortality rate in smokers with breast cancer. Further studies are needed to determine if smoking cessation can reduce the likelihood of developing pulmonary metastases in women with breast cancer.