Background: In view of studies showing that interferon alfa was effective treatment for chronic myeloid leukemia and that it prolonged survival, we organized a prospective, controlled comparative study of this treatment.
Methods: We compared recombinant interferon alfa-2a with conventional chemotherapy (hydroxyurea or busulfan) in a trial designed to have a power of 80 percent to detect a difference of 20 percent in median survival between the group given interferon and the group given conventional chemotherapy. Between 1986 and 1988, 322 patients with previously untreated or minimally treated Philadelphia chromosome-positive chronic myeloid leukemia were randomly assigned to treatment with either interferon alfa-2a (218 patients) or conventional chemotherapy (104 patients).
Results: The rate of karyotypic response (defined as > 33 percent of metaphases negative for the Philadelphia chromosome) was 30 percent in the interferon group and 5 percent in the conventional-chemotherapy group (P < 0.001). The time to progression from the chronic phase of leukemia to an accelerated or a blastic phase was longer in the interferon group than in the conventional-chemotherapy group (median, > 72 vs. 45 months; P < 0.001), as was survival (median, 72 vs. 52 months; 6-year survival, 50 percent vs. 29 percent; P = 0.002 for both comparisons). There was one treatment-related death in each group. Treatment was discontinued because of side effects (mainly influenza-like, gastrointestinal, or neurologic symptoms) in 35 patients given interferon alfa-2a (16 percent). The cost of interferon treatment was 200 times that of the conventional treatment.
Conclusions: During long-term treatment of Philadelphia chromosome-positive chronic myeloid leukemia, interferon alfa-2a induced more karyotypic responses than conventional chemotherapy, delayed disease progression longer, and prolonged overall survival more.