6-Mercaptopurine, Still Valuable for the Palliative Treatment of Acute Myeloid Leukaemia

Although 6-mercaptopurine (6-MP) is frequently used in the treatment of acute myeloid leukaemia (AML), its effect on disease progression has not been studied systematically. In a small retrospective analysis, we found that 6-MP could induce marked haematological improvement in a considerable number of AML patients who were not treated with intensive remission induction courses. Due to the inherent limitations of retrospective analyses, we then investigated prospectively in 51 consecutive patients over a 3-year period in a single centre, to what extent, oral 6-MP 250 mg twice a week could be beneficial to AML patients who were not-or no longer-eligible for intensive chemotherapy. Clinical response was scored according to changes in blood cell counts and dependency on blood transfusions. Thirteen patients (25%) were considered responders since they showed an increased platelet count from the first month after initiation of 6-MP onwards and they became independent of blood transfusions after 3 months. This effect lasted for 13 (range 7-30+) months. Median overall survival of this subgroup was 16.5 (6-33+) months. Ten patients (20%) had a shorter or incomplete response and a survival of 12 (6-30) months. Seven patients were lost to follow-up. Twenty-one (41%) failed to respond and survived for 4 (1.5-17) months. The response seemed not to be affected by previous chemotherapy, history of myelodysplasia, or karyotype abnormalities, but high leukocyte count initially was unfavourable. 6-MP thus can induce marked improvement of blood cell counts in a considerable proportion of AML patients who are not eligible for intensive chemotherapy, leading to good quality of life and a significant prolongation of survival.