If a woman smoked, contracted breast cancer, and was treated with radiation before 1980, her risk of lung cancer has been dramatically increased. Even if she did not smoke, her chances for lung cancer rose. These are the findings of a preliminary study conducted at the Columbia University College of Physicians & Surgeons by Alfred I. Neugut, MD, PhD, an associate professor of clinical medicine and public health.
The study compared 89 breast cancer patients diagnosed with lung cancer since 1986 with more than 1,000 breast cancer patients diagnosed with nonsmoking, nonradiation related malignancies during the same period. Neugut showed that the smokers with breast cancer had more than 30 times the risk of lung cancer compared with those who didn't smoke and had not received radiation.
"This is the first time that a combined risk for lung cancer from cigarette smoking and therapeutic radiation has been shown," Neugut said. "That the excess lung cancer was on the same side as the breast that was irradiated strongly indicates a causal relationship and not a statistical fluke."
Now that radiation therapy has improved, delivering narrower, more focused and contoured beams, the associated risks may be considerably lower, Neugut notes. In the widely used radiation techniques following lumpectomy, the beam is directed toward the breast tissue, away from the chest wall and lung.
Neugut's study confirms his earlier findings which showed a doubling of lung cancer risk following breast cancer radiation therapy. The current study extends these findings to stress the higher risk of lung cancer for smokers.
Still, he says, the results must be considered preliminary because there were some gaps in the data and the numbers were small. "However, the magnitude of the risk and the consistency of the findings both within the study and with our prior knowledge of the effect of radiation on the lung support the validity of the findings," Neugut said.
To verify these results, he is planning a larger scale study. Additionally, Neugut and his colleagues are exploring the combined effects of radiation therapy and smoking on patients with Hodgkin's disease and lung cancer to see if they find a similar effect.