No abstract

In studies to determine the optimal treatment for polycythemia vera, 431 previously untreated patients whose disease met established diagnostic criteria were entered into a prospective, randomized controlled trial between 1967 and 1974. Three treatment regimens were used: phlebotomy alone, chlorambucil supplemented by phlebotomy, or radioactive phosphorus supplemented by phlebotomy. Despite minor differences in age and sex, the three groups were comparable in initial hematocrit, white-cell and platelet counts, and disease-related symptoms. The median duration of follow-up is now more than 6 1/2 years. As of February 15, 1980, there were no statistically significant differences in survival among the groups. However, the risk of acute leukemia in patients given chlorambucil was 2.3 times that in patients given radioactive phosphorus and 13 times that in patients treated with phlebotomy alone. The increased incidence of leukemia during chlorambucil treatment is statistically significant (P less than or equal to 0.002); accordingly, the Polycythemia Vera Study Group has discontinued the use of chlorambucil in the treatment of polycythemia vera.

Six women presented with the clinical picture of essential thrombocythemia (ET) without the anemia, marked splenomegaly, and extreme leukocytosis characteristic of chronic myelogenous leukemia (CML). All had the Philadelphia chromosome on karyotype analysis of the bone marrow. Peripheral basophilia was present in four cases, providing a clinical clue that the Philadelphia chromosome might be present. Marrow biopsy showed granulocytic hyperplasia and either small megakaryocytes or sheets of megakaryocytes with marked atypia, findings that are more typical of CML than ET. The clinical importance of finding the Philadelphia chromosome in patients who seem to have ET is in assessing prognosis. ET generally follows a chronic, indolent course. However, five of these six patients who had the Philadelphia chromosome underwent clinical transition to the accelerated phase of CML or blastic leukemia in 4-7 years.

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