Results of a prospective study evaluating the effects of mantle irradiation on pulmonary function

Thirty patients with Stages I-III Hodgkin's disease receiving mantle irradiation were prospectively evaluated prior to therapy with spirometry, lung volumes, and tests of diffusing capacity (D_LCO). Follow-up examinations were performed at 3, 6, and 12 months and then yearly. Sixteen patients had Hodgkin's disease involving the mediastinum at presentation, 10 were smokers, and 16 received either preirradiation or postirradiation chemotherapy. Mantle doses ranged between 2300 cGy and 4000 cGy (mode of 3750 cGy) given at 150 cGy to 170 cGy tumor dose per day with split-course technique. Pulmonary function test results were translated to percent change from predicted values obtained from normal standards for each age, sex, race, and height. These percent changes were then analyzed as a linear function of time. Twenty patients have been tested ≥4 years after treatment with a median time from treatment to last pulmonary function test of 8 years. Changes over time in spirometry included an early, mild decrease in both forced vital capacity (FVC) and forced expiratory volume at 1 second (FEV₁), which returned to baseline by 2 years and then gradually decreased to a 10-15% deficit as compared with predicted values at 6-10 years. Additionally, there was a very slight decrease in FEV₁/FVC beginning at 1 year and gradually increasing to an 8% deficit at 6-10 years. Changes over time in lung volumes included a mild nadir of total lung capacity (TLC) and functional residual capacity (FRC) at 6 months to a year, which returned to baseline at 2-4 years and then gradually dropped to a 5-10% deficit at 6-10 years. Mean DLCO for the study group was 20% below predicted values prior to treatment and dropped to a low of 30% below predicted at 6 months following treatment, then gradually returned to baseline by 4 years and showed continued improvement to an overall deficit of approximately 10% at 6-10 years. With the exception of FEV₁/FVC, the changes noted in spirometry and lung volumes were of insufficient degree to be classified as abnormal. The decrease in FEV₁/FVC is indicative of a significant and progressive obstructive ventilatory defect. The effects on pulmonary function tests of smoking, the presence of mediastinal involvement by Hodgkin's disease, and exposure to chemotherapy were assessed by statistical analysis. No subset of patients demonstrated consistent evidence of a restrictive ventilatory defect expected after irradiation. All subsets of patients demonstrated baseline D_LCO values significantly below predicted values, but significant improvements over time in D_LCO were observed in patients presenting with Hodgkin's disease involving the mediastinum. The significant decrease with time in FEV₁/FVC consistent with a progressive obstructive ventilatory defect was confined to the subset of patients who smoked. Chemotherapy had no clinically significant effect on the pulmonary function test results. In summary, no significant late effects on pulmonary function attributable to mantle irradiation have been observed.