ESTIMATION OF CHRONIC PHASE DURATION IN PH-POSITIVE CHRONIC MYELOCYTIC-LEUKEMIA TREATED WITH BUSULFAN - STATISTICAL-ANALYSIS ON JAPANESE PATIENTS

Chronic phase duration was analyzed in 148 Japanese patients with Ph-p ositive chronic myelocytic leukemia (CML) treated only with busulfan, and multivariate proportional hazard models were constructed to infer the prognosis of a given patient, and to evaluate the prognostic impor tance of the clinical findings. To make an accurate estimation of an i ndividual patient's prognosis, we introduced a piecewise linear model for describing a hazard function in each prognostic variable. Of the 1 1 prognostic variables initially analyzed, the absolute count of perip heral basophils was revealed as the most important prognostic factor. A high basophil count was clearly a factor in cases with poor prognosi s. The statistical model selection based on the criteria of model appr oximation finally suggested a model with three covariates; absolute co unt of peripheral basophils, platelet count, and presence or absence o f additional chromosome abnormalities superimposed on the translocatio n of 9;22. By analyses based on the above model, we estimated that the median of the chronic phase duration for the patients with poor and g ood prognosis was 12 and 75 months, respectively. The piecewise linear model was well suited for an accurate estimation of an individual pat ient's prognosis. Thus, the model constructed here would become a reli able control to evaluate investigational approaches, such as hydroxyur ea, interferons, and/or bone marrow transplantation.