This retrospective study investigated outcomes of 404 patients with relapsed/refractory (R/R) FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD) acute myeloid leukemia (AML) enrolled in the PETHEMA registry, pre-approval of tyrosine kinase inhibitors. Most patients (63%) had received first-line intensive therapy with 3 + 7. Subsequently, patients received salvage with intensive therapy (n = 261), non-intensive therapy (n = 63) or supportive care only (n = 80). Active salvage therapy (i.e., intensive or non-intensive therapy) resulted in a complete remission (CR) or CR without hematological recovery (CRi) rate of 42%. More patients achieved a CR/CRi with intensive (48%) compared with non-intensive (19%) salvage therapy (p < 0.001). In the overall population, median overall survival (OS) was 5.5 months; 1- and 5-year OS rates were 25% and 7%. OS was significantly (p < 0.001) prolonged with intensive or non-intensive salvage therapy compared with supportive therapy, and in those achieving CR/CRi versus no responders. Of 280 evaluable patients, 61 (22%) had an allogeneic stem-cell transplant after they had achieved CR/CRi. In conclusion, in this large cohort study, salvage treatment approaches for patients with FLT3-ITD mutated R/R AML were heterogeneous. Median OS was poor with both non-intensive and intensive salvage therapy, with best long-term outcomes obtained in patients who achieved CR/CRi and subsequently underwent allogeneic stem-cell transplant.

Mutations in FLT3 are present in approximately 30% of patients with AML. The addition of midostaurin (MIDO) to intensive chemotherapy (IC) became standard of care following the RATIFY trial, but comprehensive real‐world data spanning the full adult age spectrum and including both FLT3 ‐ITD and FLT3 ‐TKD mutations remain limited. We retrospectively analyzed 1658 adults aged 14–85 years with newly diagnosed FLT3 ‐mutated AML from 129 PETHEMA registry centers: 469 received IC + MIDO and 1189 IC alone. Composite complete remission was higher with IC + MIDO than IC (81.4% vs. 71.7%; p < 0.001) and Day 30 mortality was substantially lower (2.1% vs. 7.1%; p < 0.001). Median overall survival was 47.2 versus 19.3 months (HR 0.64; 95% CI, 0.53–0.76; p < 0.001), and the benefit was sustained after multivariable adjustment (HR 0.73; p = 0.017). In 261 propensity score–matched pairs, the effect was attenuated, remaining significant for event‐free survival (HR 0.77; p = 0.029) and showing a nonsignificant trend for OS (HR 0.77; p = 0.06). Allogeneic hematopoietic stem cell transplantation in first remission was more frequent in the IC + MIDO cohort (48.9% vs. 41.3%; p = 0.023). Time‐dependent analyses showed the largest MIDO effect among autologous and non‐transplanted patients (OS HR 0.45; p = 0.138, and HR 0.69; p = 0.014, respectively). The benefit of MIDO was consistent irrespective of FLT3 mutation type, FLT3 ‐ITD allelic burden, cytogenetic risk, and gender, while less improvement occurred among NPM1 wild type and secondary AML patients. This large real‐world cohort confirms the survival benefit of MIDO plus IC across the full adult age spectrum, supporting its standard‐of‐care status in FLT3 ‐mutated AML.