Pulmonary Radiation Reaction: A Vital-Capacity and Time-Dose Study

Abstract

Abnormal pulmonary changes following radiation therapy over the lungs have long been recognized and frequently described. The object of this paper is not a description of these well known changes, but rather a report of a study of the relationship of the time-dose aspect of radiotherapy to radiation-induced fibrosis and of pulmonary vital capacity as an index of lung function in those patients with fibrosis. Consideration will also be given to various clinical aspects of the problem. Review of Literature The earliest report in this country of pulmonary changes following roentgen-ray treatment of breast carcinoma was made in 1923 by Groover, Christie, and Merritt (1). In the ensuing years many articles appeared in the literature regarding the pathology, incidence, and radiographic findings, as well as the clinical picture of pulmonary damage after irradiation of the lungs. In 1942 a comprehensive review of the effect of radiation on the lung was given by Warren (2). The pathology of radiation pulmonary reaction is very similar to that of inflammation. There are edema, congestion, inflammatory cell infiltration, desquamation of bronchial and alveolar epithelium, followed by regeneration. If the reaction is mild, the changes subside in a few weeks or months, leaving little or no residual evidence. In severe cases, the inflammatory changes become chronic and may persist for months or years. During this period, fibrosis and excessive proliferation of connective tissue predominate. Widmann (3) and Mcintosh (4) suggested that age, arteriosclerosis, previous infection, or metastasis are contributing factors in the severe pulmonary reaction. The symptoms of pulmonary radiation reaction are varied. Many people present no symptoms. Some have a cough and chest pain. Rarely, one finds a patient with malaise, fever, and dyspnea. Congestive heart failure has been reported after several years of chronic progressive pneumonitis by Freid and Goldberg (5). Leach (6) in 1943 reported that patients with chronic “pleuropneumonitis” following irradiation had “increased ventilation rate, a reduced complementary phase of vital capacity, and a low oxygen absorption.” Whitfield, Bond, and Arnott (7) stated that “maximal breathing capacity and divisions of lung volume were both reduced, though the ratio of various divisions of lung volume to total capacity was much the same as in normal persons.” One patient's arterial blood was studied and oxygen saturation was found to be normal at rest but desaturation became evident on exercise. Stone, Schwartz, and Green (8) observed 5 cases of radiation pneumonitis and fibrosis leading to severe pulmonary insufficiency. In some cases the residual air was normal and in others it was decreased. Some cases showed markedly reduced vital and total capacities. The intrapulmo-nary mixing was normal.