Randomized study on hydroxyurea alone versus hydroxyurea combined with low-dose interferon-alpha 2b for chronic myeloid leukemia. The Benelux CML Study Group.

Interferon-alpha (IFN-alpha) is considered the standard therapy for chronic myeloid leukemia (CML) patients not suitable for allogeneic stem cell transplantation. From 1987 through 1992, 195 patients in the Benelux with recent untreated CML were randomized between low-dose IFN-alpha2b (3 MIU, 5 days/wk) or hydroxyurea alone (control group). The white blood cell count had to be kept less than 10 x 10(9)/L in both arms; to this end, the IFN group received additional hydroxyurea, if necessary. The complete hematologic responses at 6 months in the IFN group were 62%, versus 38% in the control group. In the IFN group, a complete hematologic response at 6 months predicted a better survival (P = .001), but such a tendency was also seen in the control group (P = .07). Cytogenetic responses in the IFN group yielded 9% complete responders, 7% partial responders (<35% Ph+), and 24% minor responders (36% to 95% Ph+). The quality of cytogenetic response within the first 24 months was highly predictive for survival (P = .002). Twenty-four patients discontinued IFN-alpha because of side effects, but they did this at a long median interval of 17.6 months; the remaining patients did not require dose adaptations. Although the hematologic and cytogenetic responses in the IFN group were higher than in the control group, the duration of chronic phase from randomization was not statistically different with 53 and 44 months in the IFN and control group, respectively. Also, no advantage for survival calculated from diagnosis was seen for the IFN group (median, 64 months) compared with the control group (median, 68 months).