Is stem cell transplantation still needed for adult Philadelphia chromosome-positive acute lymphoblastic leukemia receiving tyrosine kinase inhibitors therapy?: A systematic review and meta-analysis

Background: Hematopoietic stem cell transplantation (HSCT) is the current mainstay treatment for Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). However, tyrosine kinase inhibitors (TKI) also play a significant role in the treatment of these patients. We conducted this systematic review and meta-analysis to compare the efficacy of allogeneic (allo-) HSCT, autologous (auto-) HSCT, and chemotherapy (CMT) alone–all in combination with TKIs in adult Ph+ ALL patients. Materials and methods: This systematic review identified studies from the EMBASE and MEDLINE databases from inception to April 2021 using search terms related to “ALL” and “HSCT.” Eligible studies could be randomized controlled trials or cohort studies that included adult Ph+ ALL patients who received a TKI and either allo-HSCT, auto-HSCT, or CMT alone, and that reported the number of patients in each group for each of our primary outcomes of interest: overall survival (OS) or disease-free survival (DFS). Point estimates and associated 95% confidence intervals (CI) from each study were combined using the Hantel-Maenszel method. Results: After two rounds of review, 26 cohort studies were determined to be eligible for the meta-analysis. Adult Ph+ ALL patients who received HSCT had better survival outcomes than those who did not receive any HSCT (pooled odds ratio [OR] for OS of 1.61, 95%CI: 1.08–2.40; I2 = 59%, and for DFS of 3.23, 95%CI: 2.00–5.23; I2 = 62% for allo-HSCT; and, pooled OR for OS of 7.04, 95%CI: 1.97–25.15; I2 = 0%, and for DFS of 5.78, 95%CI: 1.04–32.19; I2 = 42% for auto-HSCT). Allo-HSCT recipients had comparable OS and DFS, but lower relapse rate compared to auto-HSCT recipients. Funnel plot generally demonstrated no presence of publication bias. Conclusions: This systematic review and meta-analysis demonstrated superior results of HSCT in Ph+ ALL patients compared to CMT alone. Moreover, auto-HSCT could be implemented with comparable survival outcomes to allo-HSCT in patients with no available donor or when haploidentical HSCT is not feasible.