Sequential flow cytometric analysis of cellular DNA-content in peripheral blood during treatment for acute leukaemia

Sequential flow cytometric analysis (FCM) of relative nuclear DNA content per cell was done in peripheral blood of 12 patients during treatment for acute leukaemia. A marked increase of cells with S-phase DNA-content during the first hours of treatment was found in patients responding favorably to treatment. One patient with increase of 'S-phase cells' died before clinical improvement could be evaluated. However, lack of S-phase increase at one treatment cycle did not exclude a favorable response in the next. Two cases with probable aneuploid leukaemia showed gradual disappearance of abnormal cells during therapy. The value of FCM analysis of peripheral blood seems to be in predicting the response to treatment before clinical signs appear.