Hematology · Medical Literature
Efficacy and safety of mitoxantrone hydrochloride liposome/ thiotepa/ busulfan/fludarabine (MTBF) conditioning regimen for salvage allogeneic hematopoietic stem cell transplantation in patients with relapsed or refractory acute myeloid leukemia: A single - Arm prospective clinical trial.
Abstract
To investigate the efficacy and safety of MTBF as conditioning regimen for salvage allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with relapsed or refractory acute myeloid leukemia (R/R AML). We conducted a single-arm prospective clinical trial (NCT06385808). The main outcome was cumulative incidence of relapse (CIR), and the secondary outcomes were progression-free survival (PFS), overall survival (OS), engraftment time, graft-versus-host disease (GVHD), and non-hematological adverse effects. Twenty-four R/R AML patients from the First Affiliated Hospital of Xi'an Jiaotong University were enrolled, and all achieved engraftment. Mucositis was the predominant toxicity and was managed appropriately. The two-year CIR was 10%. The two-year OS and PFS were 78.9 ± 11.1% and 51.2 ± 19.3%, respectively. Two patients experienced relapse, and three patients died of infection. Subgroup analyses demonstrated that maintenance treatment post-transplantation may improve OS. The MTBF regimen for salvage allo-HSCT in R/R AML exhibited notable anti-leukemia activity and tolerable toxicity. (NCT06385808, Efficacy and Safety of MTBF Conditioning Regimen for Salvageable Allo-HSCT in the Treatment of R/R AML).
Clinical relevance
In patients with relapsed or refractory acute myeloid leukemia (R/R AML), does the MTBF conditioning regimen (mitoxantrone hydrochloride liposome / thiotepa / busulfan / fludarabine) provide effective disease control and acceptable toxicity when used as conditioning for salvage allogeneic hematopoietic stem cell transplantation (allo-HSCT)? __SNAPSHOT__ {"studyDesign":"Single-arm prospective clinical trial (NCT06385808)","setting":"Single center — First Affiliated Hospital of Xi'an Jiaotong University, China","sampleSize":"n = 24 (single arm; no comparator group)","population":"Adult patients with relapsed or refractory acute myeloid leukemia (R/R AML) proceeding to salvage allo-HSCT; specific cytogenetic/molecular risk profiles, prior lines of therapy, remission status at transplant, donor type, and age distribution not reported in the abstract","intervention":"MTBF conditioning regimen: mitoxantrone hydrochloride liposome + thiotepa + busulfan + fludarabine, administered prior to salvage allo-HSCT","comparator":"Not applicable — single-arm study with no concurrent control or comparator group","primaryOutcome":"Cumulative incidence of relapse (CIR) at two years","followUp":"Two years (minimum or median follow-up duration not reported in the abstract)","fundingSource":"Not reported"}
Key findings
All 24 enrolled patients achieved engraftment (100% engraftment rate; no confidence interval or p-value reported). The two-year cumulative incidence of relapse (CIR), the primary endpoint, was 10% (2 of 24 patients relapsed; absolute denominator-based rate = 8.3% [calculated]; the 10% figure likely reflects a competing-risk cumulative incidence estimate). Two-year overall survival (OS) was 78.9 ± 11.1% and two-year progression-free survival (PFS) was 51.2 ± 19.3% (reported as mean ± SD or SE; framing as such is atypical for Kaplan-Meier estimates and the statistical method is not explicitly clarified in the abstract). Three patients (12.5% [calculated]) died of infection, constituting the primary driver of non-relapse mortality observed. No deaths attributable to regimen-related toxicity or graft failure were reported in the abstract. Mucositis was identified as the predominant non-hematological toxicity and was described as manageable. Subgroup analyses suggested that post-transplant maintenance therapy may be associated with improved OS; however, the specific agents used, subgroup sizes, effect estimates, confidence intervals, and p-values were not reported in the abstract. NNT/NNH cannot be calculated due to the absence of a comparator arm.
Practice implications
This small, single-arm, single-center prospective trial provides early signals that the MTBF conditioning regimen may yield a low two-year relapse rate (10%) and a potentially meaningful two-year OS (~79%) in a population with R/R AML — a setting in which historical two-year OS frequently falls below 30–45% with conventional conditioning approaches. The absence of a concurrent comparator arm means that no causal attribution or superiority claim can be made; the favorable outcomes could reflect patient selection, institutional expertise, post-transplant maintenance use, or true regimen efficacy. The prominent role of infection-related mortality (3 deaths, 12.5% [calculated]) underscores the need for rigorous infectious prophylaxis and monitoring in this regimen. The gap between the two-year OS (~79%) and PFS (~51%) is substantial and warrants careful interpretation — this discordance may reflect salvage interventions rescuing patients after relapse, composite endpoint definitions, or statistical artifact related to small sample size and wide uncertainty intervals. The population most likely to benefit, the optimal post-transplant maintenance strategy, the role of MRD monitoring, and whether results are generalizable beyond this single Chinese academic center remain entirely unestablished. IMPORTANT LIMITATION: This summary is based solely on the published abstract; full-text data including patient characteristics, cytogenetic risk distribution, donor type, GVHD rates and grading, engraftment kinetics, complete toxicity profiles, statistical methodology, and subgroup analyses are not available for review, which substantially limits the rigor of interpretation. __LIMITATIONS__ Very small sample size (n = 24): critically underpowered to detect meaningful differences in secondary endpoints or to perform reliable subgroup analyses; wide uncertainty intervals implied by ± values reported for OS and PFS,Single-arm design: no concurrent control or randomized comparator; historical comparisons are subject to significant selection bias and differences in supportive care era,Single-center study from one Chinese academic institution: significant generalizability concerns regarding donor availability, HLA matching practices, GVHD prophylaxis protocols, infectious disease epidemiology, and patient selection criteria,Patient selection bias: key determinants of prognosis (cytogenetic/molecular risk, disease burden at transplant, number of prior therapy lines, remission status, donor type, MRD status) are not reported in the abstract — highly selected lower-risk patients could account for favorable outcomes,Statistical reporting ambiguity: OS and PFS are reported as 'mean ± value' which is non-standard for Kaplan-Meier survival analysis; the statistical methodology is unclear and the uncertainty intervals are very wide, limiting confidence in point estimates,Short and uncertain follow-up: whether two-year follow-up is minimum, median, or maximum is not stated; late relapses and late non-relapse mortality events may not be captured,Non-relapse mortality (NRM) not formally reported as a competing-risk endpoint; infection deaths reported individually but composite NRM estimate is absent,Subgroup analyses for maintenance therapy are exploratory, likely underpowered, and no effect estimates or p-values are reported — susceptible to type I error and post-hoc bias,Abstract-only review: full toxicity grading (CTCAE), complete GVHD incidence and severity, engraftment kinetics, MRD data, and statistical models are unavailable,Funding source not reported, precluding assessment of potential conflicts of interest __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This small single-arm prospective trial (n = 24) reports a low two-year CIR of 10% and a two-year OS of ~79% with the novel MTBF conditioning regimen for salvage allo-HSCT in R/R AML, suggesting promising anti-leukemic activity with manageable toxicity — predominantly mucositis — and infection-driven non-relapse mortality. However, the single-arm design, very small sample, single-center Chinese academic setting, and abstract-only available data preclude definitive conclusions about efficacy, safety profile, or superiority over existing conditioning strategies. The MTBF regimen warrants evaluation in larger, ideally randomized or prospectively controlled, multicenter trials before it can be considered for broader adoption outside of clinical trial settings.