Results in hairy-cell leukemia patients treated with α-interferon: Predictive prognostic factors

Fourty-four evaluable patients with hairy cell leukemia (HCL) were treated with human lymphoblastoid α-interferon (α-IFN), at a dose of 3 x 10⁶ Units a day for 12-18 months while 18 of them continued to receive a three times per week schedule at the same dose as maintenance treatment. Eighteen percent of patients achieved complete response, 64% partial response, and 18% minor response with a median duration of 37.5, 22.9 and 3.5 months respectively. Twenty patients (45%), all partial or minor responders, subsequently had progression of the disease. The progression occurred more frequently in patients who presented at diagnosis with a hairy-cell index value > 0.50 than in those who presented with a hairy-cell index <0.50: 14/26 (54%) versus 2/11 (18%) respectively. In addition, the progression rate was more evident in 'non-maintained' than in 'maintained' patients: 16/26 (61.5%) versus 4/18 (22%). Restarting α-IFN treatment in 16 of the 20 progressed patients proved effective only in 9 of them. From these findings it appears that a low hairy-cell index at diagnosis correlates favorably with a good hematological response. Furthermore, continuous therapy with α-IFN seems very useful in reducing the progression of the disease, in particular in patients with a very high hairy-cell index at diagnosis.