Characteristics and Preliminary Clinical Results of a Cohort of Patients in Santiago, Chile, Undergoing Haploidentical Hematopoietic Cell Transplantation with Postransplant Cyclophosphamide

Introduction: Haploidential hematopoietic cell transplantation (haplo HCT) with postransplant cyclophosphamide is a treatment option for hematologic cancers. Higher accessibility and lower costs compared to other alternative donors are just two advantages. Studies have shown benefits in survival, toxicity and acute and chronic graft vs host disease (GVHD) risks. Since our population is underrepresented in international registries, haplo HCT will significantly increase the possibility of transplanting patients in need.

Patients and methods: Retrospective analysis of patients with hematologic cancers who underwent haplo HCT in 2 high complexity hospitals in Santiago, Chile, between 2012 and 2014. We describe demographics, overall survival (OS), progression free survival (PFS), acute and chronic GVHD, neutrophil and platelet engraftment and transplant complications. Statistical analysis was performed with GraphPad 6.0f software.

Results: 18 patients were transplanted, with a median age of 36 years old (range, 17 - 57), and 73% males (n=13). 73% (n=13) had acute leukemias, 17% (n=3) non-Hodgkin lymphomas and 7% (n=1) Hodgkin lymphoma. 55% (n=10) were in first complete remission (CR1), 39% (n=7) in second complete remission (CR2) and 5% (n=1) in third complete remission (CR3). 89% (n=16) of the donors were 3/6 HLA compatible and 11% (n=2) 4/6 HLA compatible (intermediate resolution in A, B and DRB1). 56% (n=10) were conditioned with myeloablative (MA) regimens. All received tacrolimus, mycophenolate mophetil and postransplant cyclophosphamide as GVHD prophylaxis. The median CD34+ cell dose (10⁶ /kg of the receptor) was 6.01 (range, 1.6 - 9.5) obtained in 89% of the cases (n=15) by leukopheresis. The median time to neutrophil engraftment was 18.1 days (range, 12 - 25) without differences between MA and reduced intensity conditioning (RIC) regimens. Median time to platelet engraftment was 34 days (range, 14 - 150) with greater engraftment time after MA (median: 43 days) than RIC (median: 29 days). Incidence of grade 2-4 and 3-4 acute GVHD was 22% (n=4) and 17% (n=3), respectively. No cases of chronic GVHD have been diagnosed. Main complications after transplant include; 1 patient with sinusoidal obstruction syndrome, 1 with hemodyalisis, 11 with CMV reactivation and 8 with other infections (BK virus, C. difficile, Fusarium sp and VRE). The median follow up time was 228 days (range, 45 - 565) and 1 year OS and PFS were 56% and 59%, respectively. No differences in OS were seen when comparing patients transplanted in CR1 and CR2 (66% vs 57%, p=NS). Transplant related mortality (TRM) was 29% after 1 year of follow-up.

Conclusions: Haplo HCT is a procedure that offers a curative alternative to patients who lack matched donors. In this first report from Chile, we observed similar outcomes to other reports. Further follow-up and more patients are needed to better evaluate this procedure in the long-term.