Early treatment decisions with interferon-alfa therapy in early chronic- phase chronic myelogenous leukemia

Purpose: To determine, in patients with Philadelphia chromosome (Ph)- positive chronic myelogenous leukemia (CML) on interferon alfa (IFNα), whether combining pretreatment characteristics and early response profiles would distinguish patients with differential benefits that would allow better decisions on subsequent therapy. Patients and Methods: A total of 274 patients treated from 1982 through 1990 with IFNα regimens were analyzed. A second group of 137 patients treated with IFNα and low-dose cytarabine (ara- C) between 1990 and 1994 was later used to confirm the guidelines derived from the original study group analysis. Patients' pretreatment factors and response to IFNα therapy at 3, 6, and 12 months were analyzed in relation to subsequent achievement of major cytogenetic response. After univariate analysis of prognostic factors, a multivariate analysis selected, at 6 months, independent pretreatment factors that added to the response status in predicting subsequent outcome. The results were then applied at the 3- and 12-month periods and confirmed in the subsequent population. Results: Response to IFNα therapy at 3, 6, and 12 months was a significant predictor of later major cytogenetic response. The presence of splenomegaly ≤ 5 cm below the costal margin (BCM) or thrombocytosis ≤ 700 x 10⁹/L pretreatment added significant independent prediction to response. At 6 months, patients with a partial hematologic response (PHR) or resistant disease had a less than 10% chance of achieving a later major cytogenetic response, as were those in complete hematologic response (CHR) and who had pretreatment splenomegaly and thrombocytosis. Applying the model at 3 months showed that only patients with ≤ PHR and pretreatment splenomegaly or thrombocytosis at 3 months had such a low major cytogenetic response rate. Finally, at 12 months, patients with CHR still had a 15% to 25% chance of having a major cytogenetic response later if they did not have pretreatment splenomegaly and thrombocytosis. Conclusion: This analysis allows better selection of patients with Ph-positive CML on IFNα therapy for continuation of IFNα versus changing therapy early in the course of CML. For treatment programs that choose to change patients to other investigational therapies (eg, intensive chemotherapy and/or autologous stem-cell transplantation [SCT]), baseline outcome expectations are provided for patients continued on IFNα therapy, against which the results of new approaches can be compared.