Outcomes Of Myeloablative, T Cell Deplete Unrelated Donor Hematopoietic Stem Cell Transplantation At A Single Center.

e19525 Background: Myeloablative conditioning (MAC) and unrelated donor (UD) hematopoietic cell transplantation (HCT) are associated with increased non-relapse mortality (NRM) compared with matched related donor (MRD) HCT [18%, 21%, and 32% for MRD, Matched UD (MUD), and mismatched MUD (MMUD), respectively, p < 0.001] (Saber et al, 2012). Our center uses alemtuzumab as means of T cell depletion to mitigate NRM risk in UD HCT. Here, we report outcomes utilizing this strategy. Methods: We retrospectively analyzed adult patients (pts) who received alemtuzumab-based T cell deplete MAC UD HCT from August 2012 to December 2017. Outcomes were estimated via Kaplan Meier and cumulative incidence methods. Results: Sixty-eight pts underwent T cell deplete MAC UD HCT for AML/MDS (n = 32), ALL (n = 18), lymphoma (n = 5), and other diseases (n = 13). Thirty-nine (57.4%) underwent a MUD HCT, while 29 (42.4%) underwent a MMUD (≤ 9/10 match) HCT. Median follow up was 35.5 months (m) (range 1.5 – 71.1). Median age was 46 years (range 21 - 68), 58.8% were male. Nineteen AML pts (67.9% of all AML) were considered high risk defined as secondary AML (n = 3), CR2 or more (n = 9), primary induction failure (n = 6) or having gross residual disease at time of HCT (n = 1). At 24 m, overall survival (OS) for the entire cohort was 65.3% (95%CI (CI) 53.5%- 77.2%), GVHD relapse-free survival (GRFS) was 54.8% (CI 42.8%- 66.9%), NRM was 10.4% (CI 4.5%- 19.2%), and relapse incidence (RI) was 27.3% (CI 17.1%- 38.5%). None of the 68 pts had graft failure or rejection. In the AML/MDS cohort, at 24 m OS was 52.3% (CI 33.9%- 70.7%), GRFS was 41.4% (CI 23.9%- 59%), NRM was 9.7% (CI 2.4%- 23.2%), and RI was 39.1% (CI 21.8%- 56.2%). Non-AML/MDS pts at 24 m had OS, GRFS, NRM and RI of 76.8% (CI 62.6%- 90.9%), 66.7% (CI 51.3%- 82.08%), 11.1% (CI 3.4%- 23.9%), and 16.7% (CI 6.6%- 30.6%), respectively. The table summarizes our outcomes. Conclusions: We show that alemtuzumab-based MAC conditioning for UD HCT has the benefit of being well tolerated with low NRM and high GRFS, while having comparable RI and OS compared to published outcomes of T cell replete MAC UD HCT (Saber et al, 2012). However, the retrospective nature without a comparator is a major limitation which necessitates a future prospective study to validate these findings. [Table: see text]