Outcomes of haploidentical hematopoietic stem cell transplantation in adults aged 60 and over: a systematic review and meta-analysis

Background Haploidentical hematopoietic stem cell transplantation (HSCT) has become a viable option for older adults with hematologic malignancies lacking matched donors. However, outcomes in patients aged ≥60 years vary widely, with reported 2-year overall survival (OS) ranging from 15% to 74%. This systematic review and meta-analysis aimed to estimate pooled survival outcomes and identify factors contributing to outcome heterogeneity in older recipients of haploidentical HSCT. Methods A comprehensive systematic literature search was conducted across PubMed, Google Scholar, and Cochrane databases from inception to April 30, 2025, following PRISMA guidelines. Studies enrolling adults aged ≥60 years undergoing haploidentical HSCT with reported OS, non-relapse mortality (NRM), or relapse incidence at 1-, 2-, or 3-years were included. Meta-analyses were performed using DerSimonian-Laird random-effects models. A composite “High-Impact Trio” risk score was developed based on the prevalence of active/refractory disease, high-risk cytogenetics, and impaired performance status to explore heterogeneity through subgroup analyses and meta-regression. Results Sixteen studies (18 cohorts; 1,268 patients) were analyzed. Pooled survival estimates were: 1-year OS 62% (95% CI, 56–68%), 2-year OS 53% (95% CI, 46–60%), and 3-year OS 45% (95% CI, 38–52%). Three-year NRM and relapse incidence were 28% (95% CI, 23–34%) and 32% (95% CI, 25–40%), respectively. Significant heterogeneity was observed (I² = 71–82%); the risk score explained 39–60% of between-study variability and correlated with OS and NRM (P