20-Year Steady Increase in Survival of Adult Patients with Relapsed Philadelphia-Positive Acute Lymphoblastic Leukemia Post Allogeneic Hematopoietic Cell Transplantation

Purpose:

Relapse after allogeneic hematopoietic cell transplantation (allo-HCT) remains the first cause of transplant failure in patients with Philadelphia-positive (Ph⁺) acute lymphoblastic leukemia (ALL). In other hematologic malignancies, therapeutic advances resulted in significant improvement over time in survival of patients relapsing after transplant.

Patients and Methods:

We compared outcomes at European Society for Blood and Marrow Transplantation (EBMT) participating centers of 899 adult patients with Ph⁺ ALL who relapsed between 2000 and 2019 after allo-HCT performed in first complete remission. Median follow-up for alive patients was 56 months.

Results:

Overall, 116 patients relapsed between 2000 and 2004, 225 between 2005 and 2009, 294 between 2010 and 2014, and 264 between 2015 and 2019. Patient and transplant characteristics were similar over the four time periods except for a progressive increase in unrelated donors, peripheral blood stem cells, reduced intensity conditioning, and in vivo T-cell depletion and a progressive decrease in total body irradiation. The 2-year overall survival (OS) after relapse increased from 27.8% for patients relapsing between 2000 and 2004 to 54.8% for 2015 and 2019 (P = 0.001). A second allo-HCT within 2 years after relapse was performed in 13.9% of patients resulting in a 2-year OS of 35.9%. In multivariate analysis, OS from relapse was positively affected by a longer time from transplant to relapse and the year of relapse.

Conclusions:

We observed a major progressive improvement in OS from posttransplant relapse for patients with Ph⁺ ALL over the years, likely multifactorial including transplant-related factors, posttransplant salvage, and improvement in supportive care. These large-scale real-world data can serve as a benchmark for future studies in this setting.