TCL-150 Outcome of Stem Cell Transplantation in HTLV-1-Associated North American Adult T-Cell Leukemia/Lymphoma

Context: Adult T-cell leukemia/lymphoma (ATLL) is a rare, human T-cell lymphotropic virus 1 (HTLV-1)-driven malignancy with treatment challenges and a dismal prognosis. Allogeneic stem cell transplant (alloSCT) has shown encouraging outcomes, especially long-term survival, for ATLL patients, but data are sparse and mostly limited to Japanese patients. This is the largest experience studying the feasibility of stem cell haploidentical donors, which will greatly improve donor transplantation in ATLL outside Japan/Europe. Objectives: Comparing the outcomes of ATLL patients who underwent either autologous SCT (ASCT) or alloSCT and studying factors affecting transplant outcomes. Design: Retrospective study including patients transplanted between 2005 and 2020; median follow-up of 41 months. Setting: Tertiary oncologic center. Patients: With 116 patients, this was one of the largest ATLL cohorts in the USA; 21 patients were transplanted with 16 alloSCTs and 5 ASCTs (43% female; median age 56 years [range 39–74]; 67% Black and 29% Hispanic). Methods: Chart review. Main Outcome Measures: The 3-year relapse incidence (RI) and non-relapse mortality (NRM) were 54% and 39%, respectively, and 3-year progression-free survival (PFS) and overall survival (OS) were 27% and 35%, respectively. Results: Four out of 5 patients relapsed after ASCT, with 3 dying from disease progression and 1 lost to follow-up; 1-year RI was 80% versus 32% in alloSCT (P=0.045). In exploratory multivariate analysis, patients achieving first complete response and with good baseline performance scores had significantly better outcomes compared to their counterparts regardless of transplant type. Hispanic patients had worse outcomes, including NRM, PFS, and OS, with OS HR of 7; P=0.04. Thirteen patients died within 2 years, 3 of whom were ASCT recipients: 8 from relapse/progression, including the 3 ASCT patients, and 4 from transplant-related toxicities. Conclusions: AlloSCT led to better long-term outcomes and lower relapse rates than ASCT. Haploidentical and HTLV-1-positive donors are feasible in the absence of suitable donors. Interestingly, Hispanic patients had worse outcomes compared to Black patients in the multivariate analysis. To our knowledge, this has not been previously described and could possibly be attributed to epidemiologic genetic variations in HTLV-1 subtypes between the 2 groups. Further investigation is required, including genomic profiling of these patients.