The effect of irradiation on lung function and perfusion in patients with lung cancer.

PURPOSE: To prospectively study the changes in lung function in patients with lung carcinoma treated with relatively high doses of irradiation. METHODS AND MATERIALS: Lung function was assessed prior to and at 6 and 12 months following radiation therapy by a clinical dyspnea score, formal pulmonary function tests (lung volume spirometry and diffusion capacity) as well as an ipsilateral hemithorax lung perfusion scan. Changes in dyspnea score were evaluated by the chi-square and the Fishers exact test. Changes in formal lung function tests were compared with the t-test for dependent data and correlations with the t-test for independent data. Fifty-one patients were entered into the study. There were 42 evaluable patients at 6 months after irradiation and 22 evaluable patients at 12 months after irradiation.
RESULTS: A worsening of dyspnea score from 1 to 2, which is clinically acceptable, occurred in 50% or more of patients. However, a dyspnea score of 3, which is a serious complication, developed in only 5% of patients. The diffusion capacity (DLCO) decreased by 14% at 6 months and 12% at 12 months) (p < 0.0001). The forced vital capacity and total lung capacity decreased between 6% and 8% at 6 months and 12 months, which was statistically significant. The forced expiratory volume in 1 s decreased between 2 and 3% at 6 month and 12 months, which was not statistically significant. The ipsilateral hemithorax perfusion decreased by 17 and 20% at 6 and 12 months (p < 0.0001). There was no correlation between the initial hemithorax perfusion, or its decrease at follow up and the decrease in DLCO.
CONCLUSION: Lung irradiation results in some loss of lung function in patients with lung cancer with a projected survival of 6 months or more. The pretreatment DLCO assessment should be useful in predicting clinical tolerance to irradiation.