TREATMENT OF HAIRY CELL LEUKEMIA WITH INCREASING DOSES OF RECOMBINANT ALPHA A INTERFERON

:Since July 1984, eight patients with advanced hairy cell leukemia have received treatment with recombinant alpha A interferon. At commencement of interferon, seven patients had progressive cytopenia, and one was in leukemic phase (>20times10⁹/L circulating hairy cells). All patients had had previous splenectomy. Interferon was administered subcutaneously. The initial dose was 3times10⁶ U/day, continued until peripheral counts stabilised. Subsequently, patients received 6times10⁶ U/day, 9times10⁶ U/day, and finally 12 times 10⁶ U/day. The dose increases proceeded every 8–12 weeks, as tolerated. Seven patients had an objective response. There were four complete remissions, two partial remissions, and one minor response. Complete remission was documented only in patients on at least 6 times 10⁶ U/day for 12 weeks. The median time to complete remission was 40 weeks (range 35–53). Normalisation of peripheral blood counts preceded histologic marrow improvement. The median times for response (platelets ≤ 100 times 10⁹L, hemaglobin > 12 gm/dL, neutrophils < 1.5 times 10⁹/L), were six to eight and 17 weeks, respectively. Toxicity included myelosuppression during the first four weeks of therapy. With increasing doses of interferon, myelosuppression did not recur. A transient, mild, flu-like syndrome affected all patients. Two patients developed asymptomatic transaminitis at doses >6 times 10⁶ U/day. This resolved with dose reduction. In one case impotence was reported during the first four weeks of each interferon level. One patient discontinued after two weeks due to an exacerbation of systemic vasculitis. The median duration of treatment for the seven responding patients is 78 weeks (range 30–156). All remain on interferon without disease progression. This report confirms a high remission rate, which may reflect a dose-response phenomenon for long-term treatment with alpha interferon in hairy cell leukemia. (Aust NZ J Med 1988; 18: 557–562).