Cigarette smoking and the risk of pulmonary metastasis from breast cancer

Study objectives: To determine whether there is an association between ciga rette smoking and the development of pulmonary metastatic disease among wom en with breast cancer. Design: A case-control study. Setting: The University of California, Davis Medical Center. Participants: Eighty-seven women patients with unilateral, invasive breast cancer and pulmonary metastatic disease were identified as cases, and each patient was matched with two control patients who did not have pulmonary me tastatic disease. Case patients and control patients were matched for year of diagnosis, age at diagnosis, size of primary tumor, and nodal status. Data analysis: Multivariate analysis using conditional logistic regression was used to determine the odds of smoking among women with pulmonary metast atic disease compared to matched control patients without pulmonary metasta tic disease, after correction for potential confounding factors. Results: Thirty-eight percent of the case patients vs 29% of the control pa tients were classified as ever-smokers; 24.1% of case patients were activel y smoking at the time of breast cancer diagnosis vs 15.3% of the control pa tients. The unadjusted odds ratio for active smoking was 1.76 for women wit h pulmonary metastatic disease compared to women without pulmonary metastat ic disease (p = 0.06), In the final multivariate model, the odds ratio for active smoking among women with pulmonary metastatic disease was 1.96 (p = 0.06). Conclusions: There appears to be an association between cigarette smoking a nd the development of pulmonary metastatic disease among women with breast cancer. This may explain the previously noted higher breast cancer fatality rate among smokers. The relationship between smoking behavior and pulmonar y metastasis from breast and other cancers warrants further investigation.