Study: Smokers at Higher Risk of Breast Cancer Spreading to Lungs

Breast cancer patients who smoke are twice as likely as non-smokers to have the disease spread to their lungs, according to researchers at the University of California at Davis School of Medicine.

Researchers conducted a study of 87 women with invasive breast cancer that had spread to their lungs and compared them to 174 women with breast cancer that had not spread. Patients were matched by year of diagnosis, age at diagnosis, size of primary tumor and whether cancer was found in the lymph nodes.

Results of the study, published in the journal Chest, support previous research linking smoking to a higher risk of breast cancer spreading to the lungs, and also research showing that women who smoke are more likely to die of breast cancer than nonsmokers, even though smoking is not a risk factor for breast cancer.

"Women are in many ways more frightened of breast cancer than lung cancer, because it's so much more common. Everyone knows someone who has breast cancer," said Susan Murin, associate professor of medicine at UC Davis and author of the study. "But women are more likely to survive breast cancer if they don't smoke. If we can let them know that, it might motivate some women to quit."

Researchers are unsure of the exact mechanism for the spread of breast cancer to the lungs, but Murin suggests that cigarette smoke may make the lungs a more fertile environment for cancer cells.

"Smoking changes the immune function of the lungs and makes blood vessels more leaky. Once cancer cells escape the bloodstream, they are more likely to set up housekeeping in distant sites," said Murin.

Other sources: University of California at Davis