INFLUENCE OF SMOKING ON THE DEVELOPMENT OF LUNG METASTASES FROM BREAST-CANCER

Background. This study examined the association between cigarette smok ing status and the development of lung metastases in a group of 835 wo men diagnosed with primary malignant unilateral breast cancer. Method. Female patients with breast cancer diagnosed between 1982 and 1991 at Roswell Park Cancer Institute (RPCI) in Buffalo, New York, who provid ed information on their cigarette smoking history at the time of their diagnosis were included. The subsequent disease status of patients wa s monitored by the RPCI Tumor Registry, The Cox regression model was u sed to estimate the relationship between smoking status and the develo pment of lung metastases, adjusting for the patient's age, stage of di sease at diagnosis, and body weight. Results. Of those patients who de veloped lung metastases, 8.7% were nonsmokers, 14.1% were former smoke rs, and 14.3% were current smokers. Tests showed that nonsmokers had s ignificantly fewer lung metastases than either of the two smoking grou ps (P < 0.01). The estimated relative rates of lung metastases develop ing adjusting for age, stage, and body weight in women who smoked less than 10,000, between 10,001 and 20,000, and more than 20,000 packs ov er their lifetimes compared with nonsmokers were 1.06 (95% CI, 0.51-2. 20), 3.10 (95% CI, 1.5-6.3), and 3.73 (95% CI, 1.6-8.9) respectively. The Cox regression model showed that every 1000 packs of cigarettes co nsumed over a lifetime increased a woman's risk of developing lung met astases by about 3% to 7% (P < 0.001). Conclusion, This study found a significant association between cigarette smoking history and risk of lung metastases developing in women diagnosed with primary invasive un ilateral breast cancer. The risk of lung metastases developing increas ed as the number of cigarettes smoked in a lifetime increased.