Cladribine and mitoxantrone dose escalation in indolent non-Hodgkin's lymphoma

Since cladribine (2-chlorodeoxyadenosine [2-CdA]) and mitoxantrone both exhibit major activity against indolent lymphoid malignancies and have different mechanisms of action, we performed a dose-escalation study of 2-CdA and mitoxantrone in patients with alkylator-failed indolent lymphoma to determine the maximum-tolerated dose (MTD) of this combination and to make preliminary observations about efficacy.

Twenty-three patients were treated every 28 to 35 days, in cohorts of at least three patients, with stepwise dose escalations until dose-limiting toxicities (DLTs) were encountered. The initial dose levels were 2-CdA 0.1 mg/kg/d by continuous infusion for 7 days, mitoxantrone 5 mg/m2 intravenously (i.v.) on day 1, and prednisone 100 mg/d on days 1 to 5. Mitoxantrone was dose-escalated in increments of 2.5 mg/m2 i.v. on day 1.

The MTD of the combination was 2-CdA 0.1 mg/kg/d for 7 days, mitoxantrone 7.5 mg/m2 i.v. on day 1, and prednisone 100 mg/d on days 1 to 5. Myelosuppression and infection were the DLTs. The recommended phase II doses were 2-CdA 0.075 mg/kg/d for 7 days mitoxantrone 5 mg/m2 i.v. on day 1; prednisone was omitted to decrease the risk of opportunistic infections. The overall response rate was 70%, with 22% complete responses (CRs) and 48% partial responses (PRs). The median duration of CR was 15 months and PR 5 months.

These results demonstrate the feasibility and safety of combining 2-CdA and mitoxantrone in the treatment of indolent lymphoma, and appear to confirm clinically the mechanistic synergism and rationale for this combination regimen. Prednisone exacerbated the risk of opportunistic infection and was omitted. The overall response rate was high, including durable CRs. Further studies of this combination regimen are warranted in untreated and alkylator-failed indolent lymphoma.