Long-term results for pentostatin and cladribine treatment of hairy cell leukemia.

Over the past 25 years we have collected data at our institution from 242 patients with hairy cell leukemia (HCL), treated with pentostatin (n = 188) or cladribine (n = 54), with a median follow-up of 16 years. From this we have been able to conclude that there is no significant difference in outcome between the two agents either at first or subsequent lines of therapy. Overall, the complete response (CR) rate is 81% and the median disease-free survival (DFS) is 16 years. After relapse or non-response patients can be successfully retreated with pentostatin or cladribine achieving a lower rate of CRs with each line of therapy, although these remain equally durable. Complete response and pretreatment counts of hemoglobin >10 g/dL together with platelets >100 × 10(9)/L are associated with the longest DFS. Importantly, for patients achieving a CR the DFS is five times as long as for those achieving a partial response (PR). Patients still in CR at 5 years have only a 25% risk of relapse by 15 years. Outcomes for patients with recurrent disease have improved with the addition of rituximab to either purine analog. Overall, only eight patients have died of HCL-related causes. Patients with HCL who achieve a CR can expect a normal lifespan.