Timed Sequential Induction Therapy with Cytarabine and Mitoxantrone In Acute Myeloid Leukemia (AML): A Well-Tolerated Regimen with High Response Rates In Older Patients and Transformed AML.

Patients with AML who are eligible for chemotherapy are traditionally treated with infusional cytarabine and an anthracycline. CR rates with this combination have been approximately 50–60% with an induction mortality of 10–25%. However, this treatment is less effective in older patients in terms of CR attainment, remission duration, and overall survival.

We present a retrospective analysis of an induction regimen that was designed based on the concept of timed sequential therapy. An initial pulse of chemotherapy is administered to eradicate cells in S phase. This is followed by a rest period during which previously quiescent cells that enter the cell cycle can be targeted by a second pulse of chemotherapy. The regimen incorporates high dose cytarabine, which has been shown to improve remission duration when used in induction, and dose-intensified anthracycline therapy, which has been shown to improve outcomes in younger patients. This report highlights the responses and tolerability of the study regimen, particularly in elderly patients and patients with prior myelodysplastic syndrome (MDS).

One hundred sixty six patients were treated with timed sequential chemotherapy from 1998–2009. The treatment consisted of two doses of cytarabine 2 gm/m² IVPB over 3 hours administered 12 hours apart followed by one dose of mitoxantrone 30 mg/m² IVPB over 1 hour on days 1 and 5. Data on pre-therapy cytogenetics and MDS was collected for each patient. Remission status was assigned per the IWG response criteria for AML.

Median age of the patients was 54.5 years (range 17–85). There were eighty males and eighty-six females. Out of 166 patients, 11 (6.6%) patients had favorable, 83 (50%) had intermediate, and 72 (43.4%) had unfavorable karyotypes. One-third of the patients (57 pts) had AML transformed from MDS.

The overall response rate (ORR: CR+CRi+CRp) for all patients was 69.9%. In patients who had de novo AML, the ORR was 79.8%, regardless of age. Patients over age 60 with de novo AML had an ORR of 74%. For those patients under the age of 60, the ORR was 82%. The ORR for patients with transformed AML was 52.6% (53% in pts over age 60, 52% in pts less than 60).

The 30 day mortality rate was 3.4% (6/166). Five of the six patients who died had an unfavorable karyotype with 2 patients having therapy-related AML. The 30 day mortality for patients older than 60 was 3.3% (2/61) and for all patients was 3.6% (6/166). The 60 day mortality rate in all patients was 10.8% (18/166). Of the additional 12 patients, seven died from progressive disease and only 3 died of suspected therapy-related complications. Grade 3/4 hematologic toxicities were the most common adverse events seen.

This is a convenient, 2-day induction regimen that is well-tolerated with comparatively low 30 and 60 day mortality and high response rates in older patients and those patients with AML transformed from MDS. This would be an excellent initial regimen for remission induction in a select population of patients in whom novel consolidation or maintenance therapies can be incorporated to further improve outcome.

No relevant conflicts of interest to declare.