Long term outcome of patients with hairy cell leukemia treated with pentostatin

BACKGROUND. With the introduction of new drugs such as interferon-alpha (IF N) and purine analogs, the management of hairy cell leukemia (HCL) patients has changed. However, pentostatin has been found to produce higher complet e remission rates than IFN. The current study was undertaken to investigate response and long term follow-up in HCL patients treated with pentostatin. METHODS. Between March 1989 and October 1996, 49 patients with HCL and 1 pa tient with a HCL variant were treated with pentostatin. Eighteen patients h ad received no prior therapy, 31 patients had received prior treatment with IFN, and 1 patient had received prior treatment with 2'-chlorodeoxyadenosi ne (2'CdA) and IFN. All patients except 1 were treated with a dose of 4 mg/ m(2) every 2 weeks. The median number of cycles was 12. RESULTS. The overall response rate was 96% (48 of 50 patients); 22 patients (44%) achieved a complete response, 18 patients (36%) achieved a good part ial response (defined as residual bone marrow infiltration < 5%), 8 patient s (16%) achieved a partial response, and 2 patients died. For a median foll ow-up of 33 months off therapy, there were 5 recurrences between 12-66 mont hs; 3 of these patients were treated further with and responded to 2'CdA an d 2 died of disease progression at 12 and 40 months, respectively. In addit ion, 3 patients died of unrelated causes (1 of very early infection, 1 of t oxic death and another of cardiac arrest) comprising an overall death rate of 14% (7 of 50 patients). The overall survival rate was 86R for a median f ollow-up of 38 months (range, 8-105 months). Major side effects were febril e episodes, herpes tester, nausea/emesis, and pancytopenia. CONCLUSIONS. This analysis confirms both the high remission rate and durabl e responses that may be achieved with pentostatin treatment in HCL patients . Although pentostatin is active, the risk of cytopenia and immunosuppressi on must be evaluated carefully. Cancer 1999;85:65-71. (C) 1999 American Can cer Society.