Sequential pulmonary effects of radiotherapy detected by Tc-99m DTPA radioaerosol inhalation lung scintigraphy

Lung damage after radiation therapy in 39 female patients diagnosed with right breast cancer was measured by Tc-99m DTPA radioaerosol inhalation lung scintigraphy (DTPA). The clearance rate of Tc-99m DTPA in the lungs was presented as the clearance rate (k; %/min) of the time-activity curve of the dynamic lung images. All patients underwent simple mastectomy, and postoperative radiation of approximately 50 Gy. We divided the patients into three groups according to the interval of time between the date of irradiation and the lung scintigraphy: group 1 included 12 patients who were examined within three months after irradiation, group 2 included 16 patients who were examined 3 to 9 months after irradiation, and group 3 included 11 patients who were examined more than 9 months after irradiation. In addition, 10 age matched normal women were included as the control. The clearance of the right lung was 0.73 +/- 0.13 for normal controls, 0.94 +/- 0.24 for group 1, 1.11 +/- 0.39 for group 2, and 0.69 +/- 0.21 for group 3. In this small series of patients with breast cancer, the results suggest that lung damage may occur within the first three months after irradiation. After three months, lung damage becomes more significant and the clearance of Tc-99m DTPA in the lungs becomes faster. However, the clearance rate declines markedly after 9 months, which is assumed to result from the recovery of lung tissue from acute irradiation damage or from pulmonary fibrotic change after radiation therapy, or from a combination of both.