The Effect of Radiation on the Esophagus

Abstract

IT HAS BEEN repeatedly shown that with supervoltage equipment it is possible to damage deep-seated organs without injuring the skin. The total dosage that can be delivered to a neoplasm is thus no longer dependent upon skin tolerance but upon the tolerance of deep-lying tissues in the path of the beam. Since any tissue can be destroyed by radiation, the definition of radioresistance is a relative matter; in the past it has been defined chiefly in relation to skin tolerance. Since the advent of supervoltage therapy, there is an urgent need for quantitative knowledge regarding the dose of radiation that the different tissues can tolerate without irreversible changes that result in serious loss of function. In our experience in the treatment of intrathoracic cancer with the betatron, a major limiting factor has been the tolerance of the esophagus. During the past two years, among the patients whom we have treated for carcinoma of the lung, there were 20 who could not be adequately treated without inclusion of the esophagus within the irradiated volume. With one exception, none of this number had known esophageal extension of their disease or dysphagia prior to therapy. All exhibited clinical evidence of radiation esophagitis of varying degree. In 11 patients, the reaction was considered to be mild. This consisted of slight to moderate substernal burning beginning usually in the third week of therapy and continuing for several weeks after the completion of treatment. The pain was not severe enough to interfere seriously with nutrition but frequently required some dietary modification. Four experienced moderately severe reactions characterized by more severe pain on swallowing and lasting for two to three months after the end of therapy. Five severe reactions were manifested by marked dysphagia and the development of permanent organic strictures requiring dilatation. In 2 instances, a tracheo-esophageal fistula developed. The time of initial appearance of the dysphagia varied from the twelfth to the thirtieth day after the initiation of therapy, after the esophagus had received doses varying from 2,000 to 2,500 r in two weeks to 4,000 to 4,500 r in four weeks. The dysphagia was characterized by substernal burning following the ingestion of either solid or liquid food and lasting for several minutes or more after each swallow. In a few instances, there was only an awareness that food was passing down the esophagus. In more severe cases, the pain radiated into the chest and up into the neck and post-auricular region. Most of these patients were treated in 1954, when all of the available clinical data and animal experiments indicated that the 24-MEV x-ray beam produced by the betatron was biologically less efficient than 200-kv x-rays. At that time the report of Quastler and others (3, 4, 12, 14-18) indicated that the relative biologic efficiency for 24-MEV x-rays was from 0 6 to 0.8.