Distribution of Colloidal Radioactive Chromic Phosphate after Intracavitary Administration

Abstract

Colloidal radioactive gold, Au198, has been used for several years in the palliative treatment of patients with recurrent pleural and abdominal effusions caused by malignant neoplasm. Its use has been reasonably well established and evaluated, but the results, although encouraging, leave much to be desired. The extent of the contribution of the gamma emission of the radioactive gold to the therapeutic result is not known, but this component of the radiation produces a total-body effect that is undesirable. An isotope which, like colloidal gold 198, remains largely in the region of the injected cavity, yet has only a beta emission, would have the advantage of producing less total-body irradiation. Since the need for protecting the operator against gamma radiation complicates the use of the gold, a beta emitter would also be easier to administer. P32 with an energetic beta emission of 1.72 mev, in the form of a colloid, chromic phosphate, should be useful for this purpose. The chromic phosphate can be made in a stable colloidal form so that there is little dissociation in vitro. In evaluating the use of chromic phosphate for intracavitary injection, it is important that several questions be answered. 1. Is the material stable and not dissociated in the body following injection? 2. Is there a tendency for it to settle or plate out on pleural or peritoneal membranes, as does gold 198, or does it remain equally distributed throughout the fluid in the cavity? 3. Are there any significant hematological changes following its use in therapeutic amounts ? 4. Finally, is there any advantage over colloidal gold 198 or deep x-ray therapy in the control of recurrent effusions in patients with cancer? The present report is not an answer to all of these questions but is concerned only with efforts to gather data on the metabolism and distribution of chromic phosphate after intracavitary injection. No clinical effects are considered. Methods Four patients with pleural effusion and 6 with ascites, all of whom had cancer (proved histologically) were selected. The effusions were recurrent and necessitated paracenteses for relief. The chromic phosphate used was obtained from Abbott Laboratories. It takes several days to produce each batch, and this probably contributes to the present rather high cost. In order to obtain data on the concentration of the chromic phosphate in the fluid of the abdominal and pleural cavities at various intervals after injection, two Polyethylene tubes were placed in the cavity. Through one of these the colloid was injected; through the other samples were drawn at intervals for radioassay. The patients were instructed to turn and move around in order that the colloid might be uniformly distributed. Following intracavitary administration, the levels of radioactivity in the blood, pleural and peritoneal fluids, and urine were measured at intervals.