Complete CHR response at 24 months. (A) Proportion of patients with complete CHR over time according to treatment group. Median time to CHR was 5.7 months (IQR, 1.8-10.5 months) for HU, and 4.9 months (IQR, 2.1-8.9 months) and 6.0 months (IQR, 1.8-10.1 months) for patients treated with IFNα-2a or IFNα-2b, respectively. The CHR rate reached a maximum after 12 months among patients treated with HU (47%), whereas the CHR rate increased almost gradually over time among patients treated with IFNα-2a or IFNα-2b. (B) Proportion of patients with CHR at 24 months according to treatment group. CHR was achieved in 8 of 38 (21%; 95% CI, 10-37) patients treated with HU, 25 of 82 (30%; 95% CI, 21-42) patients treated with IFNα-2a, and in 17 of 82 (17%; 95% CI, 13-31) patients treated with IFNα-2b. No significant difference in the CHR rate was detected between HU and the two IFNα groups combined. Patients considered nonevaluable (NE) at 24 months had all discontinued the study therapy to which they were allocated, except 3 patients in whom complete diagnostic workup was not available at 24 months (HU, n = 1; IFNα-2a, n = 2). Error bars are 95% CI upper limits.