Hydroxyurea and 6-mercaptopurine in the treatment of chronic granulocytic leukemia.

: From 1975 to 1981, 92 patients with newly diagnosed Ph'-positive chronic granulocytic leukemia entered two consecutive studies. The initial trial (Study I, 1975-1978) tested the efficacy of hydroxyurea (HU) as single agent in 45 consecutive patients. In an effort to improve results obtained with HU alone, from 1978 to 1981, 47 new patients entered a second trial (Study II), which consisted of a continuous treatment with a combination of HU and 6-mercaptopurine (6-MP), at doses adjusted so as to maintain the leukocyte counts between 4 and 12 X 10(9)/L. The aim of this second study was to prolong the duration of chronic phase (CP) by the addition of 6-MP to HU and by a stricter continuous control of the size of the total granulocytic mass (TGM). Both regimens were well tolerated. Median duration of CP was 43 months in Study I and 41 months in Study II. Median survival was 51.5 months and 45 months respectively. These data indicate that neither the addition of 6-MP to HU alone, nor the effort to keep a smaller TGM, play a substantial role in postponement of blastic transformation in CGL.