Clofarabine plus cytarabine compared with cytarabine alone in older patients with relapsed or refractory acute myelogenous leukemia: results from the CLASSIC I Trial

Abstract

Purpose: To compare the receipt of clofarabine plus cytarabine (Clo+Ara-C arm) with cytarabine (Ara-C arm) in patients ≥ 55 years old with refractory or relapsed acute myelogenous leukemia (AML).

Patients and methods: Patients were randomly assigned to receive either clofarabine (Clo) 40 mg/m(2) or a placebo followed by Ara-C 1 g/m(2) for five consecutive days. The primary end point was overall survival (OS). Secondary end points included event-free survival (EFS), 4-month EFS, overall remission rate (ORR; complete remission [CR] plus CR with incomplete peripheral blood count recovery), disease-free survival (DFS), duration of remission (DOR), and safety.

Results: Among 320 patients with confirmed AML (median age, 67 years), the median OS was 6.6 months in the Clo+Ara-C arm and 6.3 months in the Ara-C arm (hazard ratio [HR], 1.00; 95% CI, 0.78 to 1.28; P = 1.00). The ORR was 46.9% in the Clo+Ara-C arm (35.2% CR) versus 22.9% in the Ara-C arm (17.8% CR; P < .01). EFS (HR: 0.63; 95% CI, 0.49 to 0.80; P < .01) and 4-month EFS (37.7% v 16.6%; P < .01) favored the Clo+Ara-C arm compared with Ara-C arm, respectively. DFS and DOR were similar in both arms. Overall 30-day mortality was 16% and 5% for CLO+Ara-C and Ara-C arms, respectively. In the Clo+Ara-C and Ara-C arms, the most common grade 3 to 4 toxicities were febrile neutropenia (47% v 35%, respectively), hypokalemia (18% v 11%, respectively), thrombocytopenia (16% v 17%, respectively), pneumonia (14% v 10%, respectively), anemia (13% v 0%, respectively), neutropenia (11% v 9%, respectively), increased AST (11% v 2%, respectively), and increased ALT (10% v 3%, respectively).

Conclusion: Although the primary end point of OS did not differ between arms, Clo+Ara-C significantly improved response rates and EFS. Study follow-up continues, and the role of clofarabine in the treatment of adult patients with AML continues to be investigated.

Fig 1.

CONSORT diagram of patient distribution in the CLASSIC I (Clofarabine and Ara-C Studying Survival via Induction and Consolidation) trial. AE, adverse event; AML, acute myelogenous leukemia; Ara-C, cytarabine; Clo+Ara-C, clofarabine plus cytarabine.

Fig 2.

Kaplan-Meier curves for (A) overall survival, (B) overall survival by random assignment strata, (C) event-free survival, and (D) event-free survival by random assignment strata. Ara-C, cytarabine; Clo+Ara-C, clofarabine plus cytarabine; HR, hazard ratio; REF, primary refractory disease or first pretrial induction remission duration < 6 months; REL, first pretrial induction remission duration ≥ 6 months.