Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation in Patients Aged 70 Years and Older: A Systematic Review and Meta-analysis.

Background: Allogeneic hematopoietic cell transplantation (allo-HCT) is a potential cure for many hematological malignancies. Historically, older adults were not considered eligible for allo-HCT due to increased toxicity and mortality concerns. This systematic review and meta-analysis aim to explore the outcomes of allo-HCT in patients aged 70 years or older.

Methods: Following PRISMA guidelines, a comprehensive literature search was performed on PubMed, Cochrane Register of Controlled Trials, and Clinicaltrials.gov using MeSH terms and keywords for "Hematopoietic Stem Cell Transplantation" AND "Outcome Assessment" from the date of inception to June 30, 2024. Our search produced 102 articles. After excluding irrelevant and review articles during primary and secondary screening, eight original studies reporting outcomes of allo-HCT in patients aged 70 years or older were included. The survival data were retrieved from Kaplan-Meier (KM) curves using an online plot digitizer tool to calculate the overall survival (OS) and disease-free survival (DFS). The pooled KM curves were plotted and analyzed using the "MetaSurvival" package of R software version 4.2.1. Proportions and 95% confidence intervals (CIs) were extracted as well.

Results: A total of 2,519 patients aged 70 years or older with allo-HCT were included in the analysis. The included patients' age ranged from 70 to 84 years, and 68% were male. Median follow-up was 23.2 (0.4-122.5) months. The combined median OS was 14.84 months (95% CI: 11.61-19.50), with OS rates at 6, 12, 24, and 36 months of 71.8%, 54.5%, 41.9%, and 34.9%, respectively. The estimated pooled mean OS was 28.62 months (95% CI: 23.41 - 31.44). The pooled median DFS was 10.54 months (95% CI: 7.93-14.17), with DFS rates at 6, 12, 24, and 36 months of 61.5%, 47.5%, 37%, and 30.6%, respectively. The estimated pooled mean DFS was 24.45 months (95% CI: 18.30 -23.74). The relapse rate ranged from 28% to 55.6%, while NRM ranged from 5.6% to 42%. The acute GvHD incidence varied from 9.3% to 32%, while chronic GvHD rates ranged from 10% to 43%.

Conclusion: Allo-HCT provides promising outcomes for patients aged 70 or older with transplant-eligible diseases. Disease progression, followed by infections, is the leading cause of mortality, underscoring the need for improved post-transplant care, including optimized GvHD regimens and strategies to reduce infection risk​.