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Hairy cell leukemia. An update on a cohort of 93 patients treated in a single institution. Effects of interferon in patients relapsing after splenectomy and in patients with or without maintenance treatment.

We retrospectively analysed the results of interferon alpha-2 (IFN) treatment in 93 patients with hairy-cell leukaemia, of which 31 had previously undergone splenectomy. Induction treatment (3 x 10(6) U three times weekly for 12 months) was completed in 84 cases (90%). Peripheral hematological response was observed in 76 patients. Two patients had persistent splenomegaly, and response was observed in both cases after splenectomy. Five additional patients were responsive after 18-24 months of induction treatment and 1 was unresponsive. Of 28 patients on maintenance treatment (1 x 10(6) U 3 x per week), no patient relapsed after a median follow-up of 30 months. The toxicity level was acceptable and IFN resistance was not observed. On the other hand, of 56 patients without maintenance treatment, 37 relapsed at a median of 19 months. Thirty of 32 evaluable patients remained responsive to a second course of IFN. Of 19 patients without relapse, 11 had undergone splenectomy compared to 0/37 patients who relapsed (p < 0.001). In conclusion, the study shows the following, (1) IFN, provides excellent palliation without major toxic side effects; (2) long term maintenance was well tolerated and prevented peripheral haematological relapse; (3) lack of maintenance treatment was associated with peripheral haematological relapse requiring a second treatment; and (4) certain previously splenectomized patients may not require maintenance treatment. These long term results must be compared with the effectiveness and toxicity of new drugs, such as pentostatin and 2-chloro-deoxy-adenosine.