Human lymphoblastoid interferon in the treatment of hairy cell leukaemia

Twelve patients with hairy cell leukaemia and peripheral cytopenias have been treated at the authors' institution with human lymphoblastoid interferon (Wellferon®) administered subcutaneously at 3 megaunits daily for 1.5-7.5 months. Three of the patients had undergone splenectomy, one had an impalpable spleen and eight had substantial splenomegaly. Eleven patients completed at least 12 weeks of treatment and were evaluable according to strict criteria for response. Two patients had a complete response, one achieved a less than complete response, five a partial response and three a minor response. Hairy cells disappeared from peripheral blood in all patients. Normalization of subnormal peripheral blood values occurred in eight out of nine patients with anaemia, in nine out of twelve with granulocytopenia, and in seven out of seven with thrombocytopenia. Four patients also had resolution of their monocytopenia. Bone marrow biopsies showed an absence of leukaemia cells in two patients and a decrease of more than 50% from pretreatment values in eight patients. These responses were associated with a return of normal haematopoiesis, but marrow reticulin fibres remained increased. In seven out of eight patients with substantial splenomegaly the spleen returned to normal (five patients) or became just palpable (two patients). No unforeseen toxicity occurred and this outpatient self-administered regimen was well tolerated. It is concluded that interferon, even at low dosages, is a highly active agent in patients with hairy cell leukaemia and that it may be an effective first-line treatment for patients with substantial splenomegaly.