- For patients less than 60, disease must have previously achieved CR and then relapsed (>20% blasts in the blood and/or bone marrow based on the WHO and/or FAB classifications as described in Appendix 9.3), excluding M3 (acute promyelocytic leukemia).). These patients must have a period of remission of >3 months (beginning with the time when the ANC >1,500/ul, platelets >100,000/ul and < 5% marrow blasts are present).