Relationship between the per cent of marrow cells in S phase and the outcome of remission-induction therapy for acute nonlymphocytic leukaemia.

The relationship between the pretherapy cell cycle characteristics of leukaemic marrow cells and the outcome of remission-induction therapy for acute nonlymphocytic leukaemia was studied in newly diagnosed and relapsed patients who were then treated with either combination chemotherapy consisting of cytosine arabinoside/anthracycline antibiotic +/- 6 thioguanine or with single agent high-dose cytosine arabinoside therapy. The outcome of high-dose cytosine arabinoside therapy was highly dependent upon the per cent of pretherapy cells in S phase with no remissions occurring in patients in whom the 3H-TdR labelling index was less than 6%. In contrast, the outcome of cytosine arabinoside/anthracycline antibiotic therapy was independent of the pretherapy cell cycle characteristics of the leukaemic cells.