Multiple myeloma with a large extramedullary plasmacytoma of the thorax treated with prednisone and radiation. metabolic balance study demonstrating unusual beneficial systemic effects of radiation ablation of the plasmacytoma.

Effects of irradiation on metabolic factors are described in a case that is cited as providing an unusual opportunity to compare the effects of prednisone alone and prednisone in conjunction with x-ray therapy on an extraskeletal thoracic plasmacytoma, as well as the myelomatous process in general. Prednisone treatment alone did not depress growth of the large expanding tumor, so supplementary treatment was given under metabolically controlled conditions. Radiation therapy (total dose, 1965 r of 250-kv x rays) caused some reduction in the size of the thoracic plasmacytoma, first noted three weeks after the first xray treatment. During the initial 10 days, while the patient received prednisone alone, he was in moderately negative nitrogen balance, averaging -- 3.46 g/24 hr. Phosphorus balance averaged -0.663 g/24 hr. Coincident with radiation therapy, there was an increase in nitrogen negativity that persisted for approximates 7 days, but was less marked following completion of radiation therapy. Urinary uric acid excretion increased slightly with the addition of x- ray therapy, but this effect was delayed until near the end of the course of radiation. Serum uric acid levels fell, reaching their lowest levels while the urinary excretion of uric acid was the greatest. To explain thesemore » findings, increased tissue destruction coincident with radiation and/or an alteration in the renal regulatory mechanism of uric acid excretion are proposed. Urinary proteins were excreted in small but relatively constant amounts with prednisone alone, but proteinuria gradually disappeared with addition of radiation. This disappearance was coincident with a fall in the abnormally elevated plasma globulin levels. The marked fall in globulins coincident with radiation therapy may be a reflection of diminished production of abnormal globulins because of destruction of plasma cell tumor tissue. With prednisone alone potassium balance average --19.4 meq/24 hr; when radiation was added, potassium balance averaged -- 24.8 meq/24 hr. Sodium balance was slightly positive during the control period and essentially in equilibrium during the first radiation treatment period. As radiation was continued, however, sodium balance became progressively more negative, reaching a maximum of --28.8 meq/24 hr Chloride balance mirrored sodium balance except that it was more negative throughout the study. Negative calcium balance persisted throughout the study, but it became markedly less with the addition of radiation to prednisone therapy. It is suggested that the decrease in the hypercalcemia and the negative calcium balance was directly related to the x-ray therapy delivered to the extramedullary plasmacytoma of the thorax. The concept that certain malignant tumors may be capable of producing a parathyroid- hormonelike substance is discussed. Suggestive evidence indicates that the plasmacytoma secreted a parathyroid-like hormone. (BBB)« less