Although chemoimmunotherapy (CIT) has substantially improved response rates, treatment free survival, and overall survival in patients with chronic lymphocytic leukemia (CLL), only 40–50% of patients achieve a complete remission and the majority have residual disease when evaluated using sensitive assays for minimal residual disease (MRD). While these facts generated interest in consolidation strategies for patients with residual disease, previous trials of alemtuzumab-based consolidation found excess morbidity/mortality. In 2008 we began a trial of lenalidomide-based consolidation for patients with previously untreated CLL who had received 6 cycles of CIT induction. Preliminary analysis suggested that lenalidomide consolidation may improve the quality of response and prolong time to retreatment (Shanafelt; ASH 2010), although follow-up was short (median 16 months).
Eligible patients were previously untreated and had CLL in need of treatment according to the NCI-WG criteria (Blood 111:5446). Treatment schema consisted of 6 cycles of pentostatin (2 mg/m2), cyclophosphamide (600 mg/m2) and rituximab (375 mg/m2) given every 21 days (Blood 109:405). All patients completing 6 cycles of PCR induction, underwent complete restaging including evaluation for MRD using sensitive flow cytometry. Patients subsequently received 6 months of lenalidomide consolidation by daily administration with a starting lenalidomide dose of 5 mg/day and escalation to 10 mg/day after the first cycle as tolerated. Patients again underwent complete restaging including MRD evaluation after 6 months of lenalidomide. At the time of restaging, MRD negative patients entered observation. Those with residual disease continued on lenalidomide and underwent repeat MRD assessment every 3 months until an MRD negative state was achieved.
45 patients were enrolled at Mayo Clinic between 3/2008 and 12/2009 of whom 44 were eligible. Median age was 65 (range: 44–78) and 71% of patients were male. 61% of patients had intermediate Rai risk and 39% high Rai risk. On prognostic testing 32% were CD38+, 52% Zap-70+, 52% IGHV unmutated, and 16% had high risk FISH (del 17p13; del 11q22). Of the 38 eligible patients who completed 6 cycles of PCR induction, 34 (89%) initiated lenalidomide consolidation. Thus by intent to treat analysis, 34/44 (77%) patients starting CIT with PCR were able to receive consolidation therapy.
Among the 34 patients who initiated consolidation, the median number of cycles of lenalidomide received was 6 (range: 1–29). Nine of 34 (26%) patients had the lenalidomide dose increased to 10 mg daily while 18 (53%) required a reduction to 5 mg every other day. Five patients are still on lenalidomide at the time of this report. No cases of tumor lysis syndrome or tumor flare reaction were observed. Adverse events deemed at least possibly related to lenalidomide consolidation included 23 (68%) patients with grade 3+ hematologic toxicity and 5 (15%) with grade 3+ non-hematologic toxicity.
Among the 34 patients who received at least 1 cycle of lendalidomide, 6 patients have improved the quality of their response including 3 patients who converted from having residual disease to a MRD- state. After a median follow-up of 29 months, 39/44 patients are alive and the median duration of response has not been reached. To date 8/44 (18%) patients have progressed to require additional treatment.
Finally, since the eligibility criteria were nearly identical to our historic trial of PCR without lenalidomide consolidation, we conducted an intent to treat analysis that compared all 44 patients in the present trial (i.e. regardless of whether they received lenalidomide consolidation) to the 64 patients previously treated on our PCR trial (Blood 109:405). The demographic and prognostic characteristics of patients in the two studies were similar. With the caveat it represents a comparison across phase II trials, the proportion of patients free of retreatment at 30 months was 79% (95% CI:67–93) for PCR followed by lenalidomide consolidation vs 66% (95% CI: 54–80) for PCR alone (Figure 1).
Lenalidomide-based consolidation for CLL patients receiving first-line CIT induction appears to improve the quality of response and prolong time to retreatment. Randomized clinical testing of lenalidomide-based consolidation appears warranted.
Shanafelt:Celgene: Research Funding; Hospira: Research Funding; Genentech: Research Funding. Off Label Use: PCR-Lenalidomide (off label use of pentostatin and lenalidomide). Tun:Celgene: Research Funding. Kay:Biothera: Research Funding; Clegene: Research Funding; Cephalon: Research Funding; Genentech: Research Funding; Glaxo Smith Kline: Research Funding; Hospira: Research Funding; Novartis: Research Funding; Supergen: Research Funding; Calistoga: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Emergent Biosolutions (Formerly Trubion): Membership on an entity's Board of Directors or advisory committees.
Asterisk with author names denotes non-ASH members.