Background: Myeloid sarcoma (MS), an extramedullary manifestation of myeloid malignancies, presents significant treatment challenges, with suboptimal outcomes reported for conventional therapies. While recent advances in allogeneic hematopoietic stem cell transplantation (allo-HSCT) have shown promise, the specific role of allogeneic peripheral blood stem cell transplantation (allo-PBSCT), especially using haploidentical donors, remains underexplored.

Methods: In this retrospective study, we analyzed 13 MS patients treated with allo-PBSCT at the Transplantation Center of the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences, Chinese Academy of Medical Sciences, between January 2012 and November 2023. Diagnoses were confirmed through tissue biopsies, and informed consent was obtained in compliance with the Declaration of Helsinki. Conditioning regimens primarily comprised modified busulfan/cyclophosphamide (Bu/Cy), with two patients receiving total body irradiation (TBI). GVHD prophylaxis involved cyclosporine, mycophenolate mofetil, methotrexate, and anti-thymocyte globulin (ATG), with tailored treatments for acute and chronic GVHD. Treatment response and survival data were monitored through regular bone marrow assessments and imaging, analyzed using Kaplan-Meier curves in R software.

Results: Among the 13 patients (5 males, 8 females; median age 26 years), 84.62% had medullary infiltration, and 76.92% had single-site extramedullary involvement. Pre-transplant, 84.62% received chemotherapy alone, and 15.38% combined chemotherapy with radiotherapy; 46.15% underwent transplantation within six months of diagnosis. At transplantation, 84.62% were in first remission, and 15.38% had minimal residual disease (MRD). The 1-year overall survival (OS) was 83.9% (95% CI, 65.7-100%), and the 5-year OS was 67.1% (95% CI, 40.7-100%), with a 5-year disease-free survival (DFS) of 80.0% (95% CI, 51.6-100%). Grade I acute GVHD (aGVHD) occurred in 53.85% of cases, Grades II-IV in 15.38%, with limited and extensive chronic GVHD (cGVHD) observed in 23.08% and 7.69%, respectively. The haploidentical group showed a 30-month OS of 85.7% (95% CI 63.3-100%) versus 62.5% (95% CI 32.0-100%) in the fully matched group (p = 0.64), with a 30-month DFS of 100% compared to 75% (95% CI 42.6-100%, p = 0.617). Transplantation within six months correlated with a 48-month and 60-month OS of 100%, significantly higher than 34.3% (95% CI 7.7-100%, p = 0.061) for those over six months. Radiation therapy recipients had a 30-month OS of 40% (95% CI 9.3-100%) versus 87.5% (95% CI 67.3-100%, p = 0.37) for non-recipients. Patients with Grade I aGVHD had a 60-month OS of 80% (95% CI, 51.6-100%), while all patients with Grade II-IV aGVHD died within 8 months of follow-up (p < 0.05). Patients with limited cGVHD had a 36-month and 60-month OS of 61.9% (95% CI 33.1-100%), while those with extensive cGVHD had a 36-month OS of 100% (p = 0.51).

Conclusion: This retrospective study underscores the effectiveness of allo-PBSCT, especially with haploidentical donors, for treating MS. Early transplantation might significantly impact survival outcomes favorably. The benefit of radiotherapy, including TBI, for prognosis remains to be further validated. Further research involving larger cohorts and prospective data collection is necessary to confirm the findings and optimize treatment protocols.

Disclosures

No relevant conflicts of interest to declare.

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2024
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