Barriers and Outcomes of Allogeneic Stem Cell Transplant (AlloSCT) for Human T Cell Lymphotropic Virus 1 (HTLV-1) Associated Adult T-Cell Lymphoma-Leukemia (ATLL) in the United States (US) from a Large Cohort in a Major Tertiary Center

Background ATLL is an aggressive T cell malignancy with dismal prognosis which occurs mainly in Caribbean immigrants in the US. AlloSCT is an effective treatment option in eligible patients (pts). We sought to identify barriers to alloSCT for these pts in a tertiary center with one of the largest ATLL populations in the US. Methods Pts with ATLL treated at Montefiore Medical Center were identified from 2003 to 2018. Comprehensive review of charts and donor registry searches were conducted. Results We identified 88 pts, mean age 56 yrs, 7 (8%) with chronic/smoldering subtypes. Of pts with acute (49, 60.5%) or lymphomatous (32, 39.5%) types, 48 (59.5%) were not considered for alloSCT due to early death (52%, n=25), lostto follow up(19%, n=10), uninsured (13%, n=7), declined HSCT (9%, n=5) and frailty (2%, n=1). Of 33 (40.7%) pts evaluated for alloSCT, 28 (34.6%) underwent HLA typing. A 10/10 matched related donor (MRD) was identified in 7 (25%). Registry search for matched unrelated donors (MUD) in the remainder 21 showed 10/10 (9.5%, n=2), 9/10 (19%, n=4), 8/10 (9.5%, n=2) and none (62%, n=13). Haploidentical donors were identified for 6 of 13 (46%) pts with no MUD. No donor options were available for 7 (25%) HLA-typed pts. AlloSCT was performed in 10/21 (47.6%) pts. Reasons for not undergoing alloSCT were progressive disease (50%, n=9), and patient declination (11%, n=2). AlloHSCT was associated with better median relapse-free (RFS) (26 vs. 11 mo, p=0.04) and overall survival (OS) (47 vs. 10 mo, p=0.03). Early transplant-related mortality (TRM) rate was 40%. Pts transplanted in complete remission (CR) and with MRD/MUD had better outcomes. Conclusion This is the first study demonstrating the barriers for alloHSCT for ATLL in the US. Only 12.3% pts proceed to alloSCT in ATLL. Early mortality, lostto follow up, uninsured status, lack of available suitable donors, including haploidentical, are significant problems. In pts who have successful induction, alloSCT can achieve long term remissions. Hence, better upfront treatments to achieve CR, early alloSCT, and consolidation/maintenance strategies in those who do not proceed to alloSCT are urgently needed to improve outcomes in ATLL.