Outcomes of hematological malignancy patients who underwent myeloablative haploidentical transplant with PTCy and ATG

e19057 Background: Haplo-HCT is a potentially curative intervention for hematological malignancies. A number of transplant platforms are used by different groups. We adopted a myeloablative conditioning (MAC) protocol, BM graft with post-transplant cyclophosphamide (PTCy) for GvHD prophylaxis as our program cares for young patients with hematologic malignancies. High grades GvHD were noticed, antithymocyte globulin (ATG) 2mg/kg was added to the platform. During COVID19 outbreak PBSCT was used as a graft source. Methods: Retrospective review of patients who underwent myeloablative Haplo-HCT for malignant hematologic disorders using ATG and PTCy for GvHD prophylaxis. Patient characteristics were summarized using frequencies for categorical variables and medians with ranges for continuous variables. Probabilities of overall survival (OS), relapsed-free survival (RFS) were summarized using Kaplan-Meier estimator with variance estimated using Greenwood’s formula. Survival curves were compared using the log-rank test. Probabilities of aGvHD, cGvHD, and extensive cGvHD were calculated using cumulative incidence function (CIF) taking into consideration DLI and death without GvHD. Probabilities of and relapse and non-relapsed mortality (NRM) were calculated using CIF taking into consideration death without GvHD and NRM and relapse as competing risks, respectively. Results: 60 patients were reviewed, 32 (53%) were males and 28 (47%) females. 57% had AML and 23% had ALL. Other diagnoses included CML, MDS, APL and BPDCN. 73% received BM graft and 27% PBSCT graft. The conditioning was myeloablative in the form of Thio/Bu/Flu (68%) for myeloid malignancies and Flu/TBI 1000 cGy (27%) for lymphoid malignancies. Most donors were males (57%) siblings (60%), with more than 50% HLA matching (58%), and no ABO mismatch (70%). Disease risk index (DRI) was intermediate in most cases (38%) followed by high (32%). At 5 years, the OS was 59% (95% CI: 46%-73%), RFS was 49% (95% CI: 34%-63%). 42% patients developed grade 2-4 aGvHD and 15% of patients developed extensive cGvHD. OS of patients > 50 years old was 21% (95% CI: 0%-56%). There were no cases of primary GF but 1 patient developed secondary GF. 17 patients developed HCYST (28%) and 17 (28%) needed ICU admission. Most patients (88%) developed CMV reactivation, and 2 patients developed VOD. We analyzed DRI, donor age, TBI vs. non-TBI, BM vs. PBSCT, donor relation, level of HLA matching, ABO mismatch, female vs. male donor, effects on OS, RFS and GvHD. None of these variables had significant association with OS. Higher DRI was associated with higher relapse (P0.04). Donor recipient sex mismatch and donor age were associated with cGvHD. Conclusions: Myeloablative Haplo-HCT for hematological malignancies with PTCy and ATG is safe and associated with acceptable OS, RFS and low rate of extensive cGvHD. Older patients require adjustment due to risk of higher NRM.