In adults with acute myeloid leukemia who achieve complete remission with one to two cycles of induction therapy, a slightly longer course of idarubicin during consolidation therapy increases leukemia-free survival without increasing nonhematologic toxicity, according to new findings.
The optimal dose of anthracyclines, such as idarubicin, during consolidation therapy in this patient population has not been explored to date. Researchers performed a randomized phase III clinical trial, comparing standard (2-day) idarubicin with increased (3-day) idarubicin during consolidation therapy with cytarabine and etoposide.
The 7-year trial involved 293 patients, aged 15-60 years (median age, 45 years), who were treated at 23 Australian hospitals after achieving complete remission with one to two courses of intensive cytarabine-based induction therapy. Study participants were randomly assigned to receive either standard or intensive idarubicin, said Kenneth F. Bradstock, MB, PhD, of the University of Sydney, Australia, and his associates.
More patients who were receiving the higher cumulative dose of idarubicin had leukemia-free survival at 3 years (47%), compared with the standard-dose group (35%), for a hazard ratio of 0.74 favoring intensive idarubicin. The estimated median leukemia-free survival was 2.13 years for intensified idarubicin, compared with 0.93 years for standard idarubicin (J Clin Oncol. 2017 Apr 3. doi: 10.1200/JCO.2016.70.6374).
Additionally, the time to relapse was significantly longer for intensive idarubicin (17 months) than for standard idarubicin (10 months). This study was not powered to detect a difference between the two groups in overall survival.
There was no significant difference between the two study groups in the incidence of serious nonhematologic toxicities or in the rate of treatment-related death, even though the patients receiving intensive idarubicin showed a clear increase in myelotoxicity, as expected.
In exploratory analyses, the researchers could not detect a specific benefit of increased idarubicin dose in any patient subgroups, in particular, younger versus older ages, adverse versus intermediate karyotypes, and mutations in the FLT3 and NPM1 genes. However, they were limited because of the low number of cases in some subgroups.
The trial was supported by the National Health and Medical Research Council of Australia, Pfizer Australia, and Amgen Australia. Dr. Bradstock reported ties to Amgen Australia. His is associates reported ties to numerous industry sources.