Response and Recovery of Liver to Radiation as Demonstrated by Photoscans

Abstract

The commonly used liver function tests are insensitive parameters of hepatic radiation response in the intact patient, particularly to treatment portals which include 50 per cent or less of the liver. This is due in part to their dependence, to a great degree, on the functional state of this organ as a whole. Symptoms due to liver irradiation are seldom encountered in practice, although the liver is included, in entirety or in part, in the treatment field during a course of radiotherapy for many abdominal, thoracic, or testicular malignant tumors. The apparent refractoriness of this organ to ionizing radiation in the usual clinical situation may be explained as follows: (a) the liver manifests nonsynchronous cyclic alterations of its cells in the mitotic phases, and the cells in the various stages of mitosis vary in radiosensitivity, (b) historically, the liver has been reputed to have enormous repair capacity following radiation injury (1), as well as after other forms of injury, and (c) the usual radiotherapeutic regimen delivers relatively low dose/time values (2,000 to 3,500 rads in three to five weeks) ordinarily to less than 50 to 70 per cent of the organ (2). One of the authors (J. A. U.) made the initial literature description of the ablation of photodensity of radiogold (Au198) and/or rose bengal (I131) liver photoscans of 5 patients, obtained during or immediately after a course of irradiation to the retroperitoneal nodes for testicular cancer (3). Further investigation seemed mandatory, and accordingly we undertook to study this phenomenon in greater detail and on a larger group of patients given radiation treatments over the liver for malignant disease. The primary aim was the evaluation of this technic for the assessment of liver damage from therapeutic external irradiation. Secondary goals were (a) to compare the sensitivity of the photoscan and clinical chemical technics, (b) to determine the radiosensitivity of the two systems involved, the reticuloendothelial by the radiogold and the hepatocellular by the rose bengal scans, and (c) to determine the radiation tolerance of the liver as measured by the ablation of photodensity in the irradiated segment, as well as the time required for return of function as measured by reappearance of the photodensity. Method and Material Radiogold and/or rose bengal liver photoscanning procedures were performed on 39 patients, 31 of whom were referred for Co60 telecurietherapy to abdominal lymph node stations as part of the treatment regimen for testicular carcinoma. Eight patients were referred for radiotherapy in connection with the treatment of bronchial, esophageal, gastric, ovarian, or pancreatic cancer. A total of 48 radio-gold and 41 rose bengal scans were obtained on these 39 patients. Thirty-one patients were studied at least once, using conventional liver function tests including alkaline phosphatase, bromosulfophthalein, prothrombin time, and transaminase.