Secondary acute myeloid leukemia (s-AML) is associated with inferior outcomes with conventional chemotherapy, and fludarabine combinations (FLAG-Ida) have been tested to improve results. More recently, CPX-351 resulted superior to conventional 3 + 7 in s-AML patients. In the UK NCRI AML19 trial, AML patients were randomized to receive either FLAG-Ida or CPX-351. Subgroup analysis revealed better overall survival (OS) with CPX-351 in patients with MDS-related gene mutations. Unfortunately, minimal residual disease (MRD) was evaluated only in a minority of patients. The aim of this study was to further disclose the mechanisms of higher efficacy of CPX-351 in s-AML, with a focus on MRD. We analyzed 183 consecutive s-AML elderly patients (median age 69, range 60-77) treated with CPX-351 (n = 82) or receiving FLAG-Ida (n = 101). Complete remission (CR) rate and MRD negativity probability were higher among patients receiving CPX-351 (MRD negative CR rate of 40/64, 62.5%, compared to 25/55, 45% in patients who received FLAG-Ida, p < 0.05). Extra-hematological toxicity was lower in CPX-351 arm, and 30 days mortality was 3.6% and 8% in patients receiving CPX-351 or FLAG-Ida, respectively. Notably, 21/64 (32.8%) CR patients treated with CPX 351 underwent allogeneic stem cell transplantation (HSCT), compared to 5/55 with FLAG-Ida (9%, p < 0.05). Overall, CPX-351 treatment resulted in higher OS (median OS 17.7 vs. 11.2 months with FLAG-Ida, p < 0.05). The better outcome of CPX-351 compared to FLAG-Ida in our cohort may be explained by a greater probability of MRD negativity, alongside with an improved tolerance, enabling more s-AML patients to undergo HSCT.
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