Allogeneic Hematopoietic Stem Cell Transplantation in Patients with Acute Lymphoblastic Leukemia and Karnofsky Performance Status Score Equal or Lower Than 80%. a Study from the Acute Leukemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT)

Recently, an increasing number of patients with acute lymphoblastic leukemia with a poor Karnofsky Performance Status (KPS) score are considered for allogeneic hematopoietic stem cell transplantation (allo-HCT). Nevertheless, there is paucity of available data about outcome of this fragile population. We report here the results of a retrospective study designed to evaluate outcome of ALL patients undergoing allo-HCT with KPS score ≤80%. The analysis included ALL patients aged ≥18 years, undergoing allo-HCT in first remission between 2000 and 2018, with a KPS score of 50% to 80% at the time of transplant. Patients who received manipulated grafts or had incomplete data about cytogenetics were excluded. Conditioning intensity was defined according to EBMT definitions (Aoudjhane M. et al, Leukemia 2005; 19: pp. 2304-2312).

A total of 1,010 patients were identified. Median age at transplant was 43 years (18-76 years). Median year of transplant was 2011. The KPS score was =80% in 83% of the patients and <80% in 17% of the patients. Diagnosis was Philadelphia chromosome (Ph) negative B-ALL, Ph positive B-ALL or T-ALL in 34%, 44% and 22% of the patients, respectively. Donor type was MSD or 10/10 UD in 60% and 40% of the patients, respectively. Conditioning was myeloablative (MAC) or reduced-intensity (RIC) in 78% and 22% of the patients, respectively, and it was TBI-based in 79% of the patients. Stem cell source was PBSC in 76% and BM in 24% of the patients, respectively. Anti-thymocyte globulin (ATG) was administered to 21% of the patients receiving MSD and 68% of the patients receiving 10/10 UD as donor type. Cumulative incidence of grade II-IV and III-IV aGVHD was 32% and 9%, respectively. The 2-year cumulative incidence of chronic GVHD (cGvHD) and severe cGVHD was 43% and 18%, respectively. Non relapse mortality (NRM) and relapse incidence (RI) at 2 years were 18% and 28%, respectively. At 2 years, leukemia-free survival (LFS), overall survival (OS) and GVHD-free, relapse-free survival (GRFS) rates were 54%, 64% and 41%, respectively.

On multivariate analysis, transplant from 10/10 UD was associated with higher incidence of aGVHD (HR 1.8, p<0.0001) and higher risk of NRM (HR 1.7, p<0.01) as compared to MSD. RIC conditioning was associated with higher risk of relapse (HR 1.2, p=0.02), lower LFS (HR 1.3, p=0.03) and lower GRFS (HR 1.3 p=0.02) as compared to MAC. NRM was not significantly different between MAC and RIC. Factors independently associated with improved OS were younger age at transplant, female sex, more recent year of transplant and Ph+ B ALL phenotype. Administration of ATG was associated with reduced risk of developing grade II-IV aGVHD (HR 0.6, p<0.001), cGVHD (HR 0.5, p<10^-4) and severe cGVHD (HR 0.4, p<10^-4).

In conclusion, allo-HCT is feasible in patients with acute lymphoblastic leukemia in first remission and KPS score ≤80%, with acceptable NRM and survival rates. Transplant from a sibling donor was associated with reduced risk of NRM and aGVHD as compared to matched unrelated donor. Interestingly, despite the poor KPS score of the patients included in the analysis, a MAC protocol was associated with similar NRM, lower relapse and better LFS and GRFS as compared to RIC in the selected population. Finally, administration of ATG was associated with reduced acute and chronic GVHD rates.