Editorial Radiophosphorous Therapy in Polycythemia

By BARUCH MODAN I HE USE of pa2 in the therapy of polycythemia vera has continued to be a controversial subject since it was first introduced.15”5 Although considered as the ultimate treatment for polycythemia vera by many hematologists it has, on the other hand, been discredited by others as being responsible for a high proportion of deaths from acute leukemia. The main obstacle to an objective evaluation of the efficacy of P has been the lack of a well-controlled clinical trial. One supposes that such a study would have been conducted when this radiotherapeutic method was first introduced, but unfortunately it never was. In view of the growing skepticism regarding the net therapeutic effect of P , it was felt that an evaluation of this kind was justified, especially because of the increasing use of radioactive materials in general. However, it seemed that for a clinical trial to be well designed, a preliminary retrospective evaluation of the presumed complications would be desirable. A large-scale study,#{176} based on the past experiences of 1222 patients, with various types of polycythemia, treated in 7 different clinics and receiving different forms of treatment, was recently carried out in the attempt to determine whether patients with polycythemia vera were indeed subjected to a higher risk of developing acute leukemia and whether tile increased risk was related to the p32 and/or x-ray treatment employed. An extensive follow-up ranging from 8 to 25 years revealed a 10 per cent minimum frequency of acute leukemia among 228 P32-treated and 72 x-raytreated polycythemia vera patients, but only 1 case of acute leukemia among 133 patients treated by means other than radiation. Leukemia frequencies of the same order of magnitude were found in a group of patients treated with 32 and in whom the diagnosis of polycythemia vera was uncertain; most of these were patients with benign erythrocytosis.7 No cases of acute leukemia were found among 301 patients in tile latter diagnostic group who received no radiation. These findings led to the conclusion that ionizing irradiation bore a direct relationship to the development of acute leukemia. Further analysis disclosed that, contrary to the prevalent assumption, neither the length of survival nor the severity of the disease played a major role in the development of the leukemic process. A no less crucial point, was the fact that the length of survival of the p32 treated patients was not found to be significantly superior to that of the ones receiving no radiation treatment. The above observation appears to be of utmost importance with regard to the argument stressed by Osgood8 that