The Effects of Radiation Therapy on Pulmonary Function in Carcinoma of the Lung

PULMONARY changes following radiation therapy for carcinoma of the lung were recognized as early as 1898 (2) and have been described frequently since then. Clinical changes indicating the development of radiation pneumonitis have been elucidated in many case reports of patients so treated. More recently, there has been renewed interest in the problem of the sequelae related to radiation therapy for pulmonary cancer and in the possible avoidance of undesired side-effects. The effects of irradiation upon lung function have been reported by MacIntosh and Spitz (16) in 1939, Baldwin et al. (1) in 1949, Whitfield and his co-workers (26) in 1954, Rubin et al. (20) in 1958, and Voutilainen et al. (24) in 1962. Even though the pathologic changes in pulmonary tissue following thoracic irradiation have been adequately documented, no systematic examination of pulmonary function has been performed in patients undergoing radiotherapy for carcinoma of the lung. The purpose of this study was to evaluate the effects of this irradiation in terms of changes at one month in studies of lung volumes, the mechanics of breathing, ventilation, arterial blood gases, and breath-holding pulmonary diffusing capacity. Methods And Material In the interval from October 1962 through October 1964, 14 patients with carcinoma of the lung treated with radiation therapy were evaluated in terms of numerous tests of pulmonary function. The tissue diagnosis was established in all instances: 8 squamous-cell carcinomas, 5 undifferentiated carcinomas, and 1 oatcell carcinoma. There were 13 males and 1 female in the study, and the median age was fifty-eight years (Table I). Eleven patients treated with the Van de Graaff generator received a median dose of 5,200 rads in a median elapsed time of thirty-four days. Four patients were treated with a 250-kv constant potential device with a half-value layer of 3 mm Cu, receiving a median dose of 3,200 rads in a median elapsed time of eighteen days. With the 2-million volt Van de Graaff generator, parallel opposed portals were utilized, the size being determined by the extent of the pulmonary lesion, with the mediastinum and hili included in the fields of treatment. In patients treated with the 250-kv constant potential device, multiple portals were utilized and a volume distribution of dosage was calculated after localization. All patients have been followed at regular intervals, but this report is limited to the changes in pulmonary function four weeks after the completion of radiation therapy. The following pulmonary function studies were performed before and after treatment: a. The vital capacity (VC) and the functional residual capacity (FRC) by the closed circuit helium dilution method of McMichael (17).