Chronic myelogeneous leukemia (CML) is genetically characterized by fusion of the bcr and abl genes on chromosomes 22 and 9, respectively. In most cases, the fusion involves a reciprocal translocation t(9;22)(q34;q11), which produces the cytogenetically distinctive Philadelphia chromosome (Ph1). Fusion can be detected by Southern (DNA) analysis or by in vitro amplification of the messenger RNA from the fusion gene with polymerase chain reaction (PCR). These techniques are sensitive but cannot be applied to single cells. Two-color fluorescence in situ hybridization (FISH) was used with probes from portions of the bcr and abl genes to detect the bcr-abl fusion in individual blood and bone marrow cells from six patients. The fusion event was detected in all samples analyzed, of which three were cytogenetically Ph1-negative. One of the Ph1-negative samples was also PCR-negative. This approach is fast and sensitive, and provides potential for determining the frequency of the abnormality in different cell lineages.

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Background. Improved survival of children with acute lymphoblastic leukemia (ALL) has made it more difficult to develop new protocols to further improve results. The authors report the pilot experience with the Memorial Sloan‐Kettering‐New York‐II (MSK‐NY‐II) protocol, based on the New York regimen with changes made in an attempt to improve efficacy while reducing toxicity. Methods. Forty‐four of 46 consecutive patients were randomized to one of four regimens varying only in the sequence and mode of administration of the drugs during the first 48 hours of therapy, while the kinetics of the disappearance of the leukemic cells from the bone marrow was monitored with bone marrow aspirates and biopsies on days 0, 2, 7, and 14. Results. Thirty‐two high‐risk and 12 average‐risk patients were randomized. The marrow contained less than 25% blasts in 74.4% and 92.9% by day 7 and 14, respectively. Ninety‐three percent achieved remission. Regimens beginning with daunorubicin achieved a greater and more rapid reduction in leukemic cells than those starting with cyclophosphamide. Daunorubicin infusion produced a more rapid cytoreduction than daunorubicin bolus. Two of 41 patients who achieved remission relapsed, and there was one death in remission. With a median follow‐up of 54+ months, the event‐free survival (EFS) rate was 86% ± 10%. Disease‐free survival (DFS) rate at 48 months was 93%. The estimated 4‐year EFS rate for the high‐risk and average‐risk patients were 83 ± 14% and 93 ± 10%, respectively. Four of 18 patients given daunorubicin bolus and 0 of 18 patients given daunorubicin infusion who were monitored with serial echocardiograms had significant decrease in cardiac function (P = 0.10). The major toxicity of the therapy was infections, with 35% of patients developing serious infections during induction and consolidation. Half the patients had an episode of bacteremia from the venous catheter during the 2 years of maintenance. Conclusions. Close monitoring of kinetics of cytoreduction can rapidly distinguish between similar therapies, and the surrogate end‐point may reduce the need for the long follow‐up periods that may still be required to demonstrate differences in EFS. Continuous infusion of daunorubicin had less cardiotoxicity with faster antileukemic activity than bolus infusion. The MSK‐NY‐II protocol with an 86% 4‐year EFS rate and a 95% DFS rate was a promising new regimen for the treatment of average‐risk and high‐risk ALL.