Long-term results of alpha interferon as initial therapy and splenectomy as consolidation therapy in patients with hairy cell leukemia. Final report from the Italian Cooperative Group for HCL.

Purpose: In 1987 the Italian Cooperative Group for the Study of hairy cell leukemia (HCL) started a prospective trial with the following three major aims: 1) to confirm the effectiveness of alpha-IFN as first-line treatment; 2) to assess the usefulness of splenectomy as consolidation treatment in patients achieving a satisfactory partial remission (PR) with alpha-IFN, and 3) to explore whether splenectomy in patients achieving complete remission (CR) with alpha-IFN can reduce the risk of relapse after discontinuation of the drug.

Patients And Methods: One-hundred seventy-seven patients with histologically-confirmed HCL were registered in the HCL88-A trial between December 1987 and January 1992. Inclusion criteria included no previous treatment and age less than 66 years. All patients received total doses of 3 MU of alpha-IFN daily for 12 months except for those who achieved early CR and would stop treatment after 6 or 9 months. Patients could be treated with different alpha-IFNs. At the time of the present analysis, 166 patients (93.8%) were fully evaluable.

Results: Treatment of HCL patients with alpha-IFN at the onset of the disease resulted in 28 CR (16.9%), 103 PR (62.0%), and 27 Minor Remissions (MR) (16.3%). Patients treated with different alpha-IFNs achieved similar results: the overall response rate (CR + PR + MR) was 92.7%, 97.2%, and 95.3% for patients treated with r-alpha-2a, r-alpha 2b, and alpha-N1, respectively. The presence of a leukemic phase and a poor performance status were associated with a statistically significant lower response rate. Patients who were randomly assigned and underwent splenectomy after achieving a PR had a better but not significant 4-year progression-free survival than cases randomized for observation (53% vs. 22%, p = 0.116). Overall, 5 patients died after study entry, with an actuarial 5-year survival rate of 96% for the entire group of 166 patients. After a mean follow-up time of 38 months, only one second malignancy has been recorded.

Conclusions: Initial therapy with alpha-IFN, regardless of the type of alpha-IFN used, induces satisfactory responses in the majority of patients with HCL, but in most instances discontinuation of treatment results in recurrence of disease. In most cases alpha-IFN improves the performance status of patients and favors a satisfactory bone marrow recovery and thus could still play a role in the initial management of the disease. Although splenectomy following alpha-IFN could prolong the progression free survival, its use should be restricted to selected cases.