Adult acute non-lymphoblastic leukaemia: reliability and prognostic significance of pretreatment bone marrow S-phase size determined by flow cytofluorometry.

46 adult patients with non-lymphoblastic acute leukaemia (AnLL) had pretreatment proliferative activity of bone marrow (BM) blasts determined simultaneously with propidium iodide DNA flow cytofluorometry (as the percentage of cells with DNA content intermediate between the diploid and the tetraploid values, 2n-4n cell %) and in vitro tritiated thymidine cytoautoradiography (as the labelling index, LI). They were then treated with the same chemotherapy regimen, including 2-3 courses of sequential vincristine, arabinosylcytosine and adriamycin, for response induction, and monthly courses of different cytostatics for maintenance. Median 2n-4n cell % was 9.9 and median LI was 5.9. A close linear relationship (r = 0.913, p less than 0.001) between the two parameters was found. Patients having a 2n-4n cell % greater than 15.6 responded more often to chemotherapy than patients having a lower percentage (p less than 0.05) but also experienced a shorter duration of first response (p less than 0.05). Overall survival was longer in patients with 2n-4n cell % greater than 15.6 (p less than 0.02). Multiple regression analysis indicates that 2n-4n cell % is a statistically significant (p less than 0.05) independent factor correlating with duration of response in adult AnLL.