Allogeneic Hematopoietic Stem Cell Transplantation (aHSCT) In Adult Patients With Acute Lymphoblastic Leukemia (ALL): Experience Of The Hematology-Oncology Department At Pontificia Universidad Católica De Chile Between 1994 and 2013

Introduction: In adult patients with high risk ALL, defined as Philadelphia cromosome ALL (Phi+) or slow response to chemotherapy, sibling donor aHSCT in first remission is recommended as consolidation treatment after achieving a complete remission. Still is unclear what other subgroup of adult patients benefit the most from aHSCT.

Objectives: The primary objective was to describe the clinical outcomes of ALL patients after aHSCT in our center, including overall survival (OS), relapse-free-survival (RFS) and transplant-related-mortality (TRM) .

Results: Between 1994 and 2013, 37 patients with ALL were transplanted, 16 Phi+ and 21 Phi-. Two patients had a second transplant for relapsed ALL Phi+, therefore 39 aHSCT procedures for ALL have been performed in our center. The average age is 33 yo (range: 17-56) and 68% were male patients (n=25). Phi+ patients were mostly >30 yo (63%, n=10), as compared to Phi- that were mostly ≤30 yo (67%, n=14). Most transplants were performed in first remission (70%, n=22), under myeloablative conditioning regimen in 92% (n=34). Reduced intensity conditioning (RIC) regimen was used because of age (n=1; Phi-) and relapse (n=2; Phi+). GVHD prophylaxis consisted of cyclosporin A and methotrexate in all the patients. Among Phi+ patients, 69% (n=11) had TKI prior to aHSCT. Only 25% (n=4) received TKI as maintenance therapy after aHSCT. Average CD34 dose collected by leukapheresis was 5.5x10⁶/kg (range: 2,14–9,16x10⁶/kg), with mean platelet engraftment at day 15 after transplant (range: 8-25 days) and mean neutrophil engraftment at day 16 after transplant (no filgrastim is used after transplant) (range: 10-22 days). In Phi+ patients, 3-year EFS and OS was 49% and 64%, respectively. In Phi- patients 3-year EFS and OS was 40% and 43%, respectively. One year TRM was 14% in Phi- and 21% in Phi+ ALL patients. Univariate analysis failed to show a correlation between RFS and OS with pre and post aHSCT minimal residual disease as measured by multicolor flow cytometry and PCR (in Phi+ ALL patientes) or remission status (CR1 vs CR≥2).

Conclusions: Our data on the outcomes of ALL patients were consistent with that reported in literature. In our series, OS in Phi+ patients was superior to those with Phi-, we speculated that it may be at least in part due to disease erradication by TKI. Our data support our practice of offering aHSCT early in the disease course for patients with ALL patients, specially Ph+ ALL patients.