Interferon alfa as primary treatment of chronic myeloid leukemia: long-term follow-up of 71 patients observed in a single center

Abstract

The purpose of this study was to evaluate the long-term outcome of interferon (IFN) alfa treatment in patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML). Between 1984 and 1990, a total of 71 patients with newly diagnosed CML had been enrolled into two consecutive IFN trials at our institution. Follow-up extended to December 1998, resulting in a median observation period for surviving patients of 11.4 years. The median survival time from diagnosis was 5.9 years. A plateau in the actuarial survival curve was found from 8.2 to 12.3 years following diagnosis with a projected 10-year survival rate of 32%. ‘Landmark’ studies showed a significant survival advantage for patients with karyotype responses. Of 68 patients accessible to calculation of the Hasford score, three were in the high risk group, 24 belonged to the medium risk group, and 41 had low risk features. The majority of cytogenetic responders including all eight assessable patients in complete cytogenetic remission were in the low risk group. Achieving a cytogenetic remission was found to provide a survival advantage also for patients with low risk disease. Of the seven patients surviving more than 11 years, six were in continuous complete cytogenetic remission. Their favorable outcome appears to translate into an out-flattening of the survival curve for the 71 single center patients presented. It will be of interest to see whether prolonged follow-ups of the large multicentric randomized trials will similarly show a subset of long-term surviving patients with ongoing IFN-induced remission.