Effects of therapeutic irradiation delivered in early childhood upon subsequent lung function.

To determine the long-term effects of therapeutic pulmonary irradiation and treatment with actinomycin D during a period of lung growth, 12 patients treated for Wilms' tumor metastatic to the lung and 8 patients treated for Wilms' tumor with no evidence of pulmonary metastases were studied 7 to 14 years after their initial tumor therapy. All patients had received irradiation to the tumor bed and treatment with actinomycin D. Group 1 had received a single course of bilateral pulmonary irradiation; group 2 had received additional pulmonary irradiation and/or thoracic surgery; group 3 had received no therapeutic irradiation directed primarily to the chest. Total lung capacity (TLC) averaged 71% of predicted value in group 1, 58% in group 2, and 94% in group 3. Diffusing capacity in groups 1 and 2 was reduced to the same extent as lung volume. Quasi-static pressure-volume relationships, studied in three of six patients in group 1, were within the normal range when lung volume was expressed as percentage of observed TLC. Airway resistance, evaluated by spirometry, maximum expiratory flow-volume curves, and resistance of the total respiratory system, was normal or reduced. The data support the hypothesis that therapeutic irradiation during a period of lung growth primarily affects the lung parenchyma and produces a decrease in subsequent size of both the lung and chest wall. No effect of actinomycin D alone upon the lung could be demonstrated.