Thiotepa-Based Conditioning for Haploidentical Hematopoietic Stem Cell Transplantation in Older Patients With Severe Aplastic Anemia

Severe aplastic anemia is a bone marrow failure disorder characterized by reduced blood cell production. For participants who need transplantation and do not have a fully matched sibling donor, haploidentical hematopoietic stem cell transplantation is an important treatment option. Older participants may have reduced organ function, a higher risk of infection, and lower tolerance of intensive treatment.

Thiotepa-based conditioning regimens are used in routine clinical practice before transplantation. In this study, the treating clinical team independently determines the conditioning regimen, medication doses and schedules, prevention of graft-versus-host disease, and supportive care according to each participant's clinical condition. Study participation does not assign, require, or change any treatment.

This is a prospective, single-center observational cohort study. The study will consecutively include participants aged 50 years or older with severe or very severe aplastic anemia who receive haploidentical hematopoietic stem cell transplantation with thiotepa-based conditioning at Peking University People's Hospital. Routine clinical information, transplantation information, and routinely collected follow-up information will be recorded through 1 year after transplantation.

The primary outcome is transplant-related mortality within 1 year after transplantation. Secondary outcomes include overall survival, hematopoietic engraftment, graft failure, acute and chronic graft-versus-host disease, cytomegalovirus and Epstein-Barr virus reactivation, serious infections, and serious adverse events. The study will not add treatment, examinations, blood collection, or follow-up visits beyond routine care.

Inclusion criteria

• Age 50 years or older at transplantation.
• Diagnosis of severe aplastic anemia or very severe aplastic anemia.
• Planned to undergo haploidentical hematopoietic stem cell transplantation at Peking University People's Hospital.
• The treating clinical team has independently selected a thiotepa-based conditioning regimen as part of routine clinical care before study enrollment.
• Required baseline and transplantation information is available in the medical record.

Exclusion criteria

• Diagnosis or transplantation type does not meet the study eligibility criteria.
• The conditioning regimen does not include thiotepa.
• Essential baseline information is unavailable, such that study eligibility cannot be determined.
• For a participant with more than one transplantation episode, only the first episode meeting all eligibility criteria will be included in the analysis.