Impact of Human T-Cell Lymphotropic Virus Infection on Survival Following Stem Cell Transplantation

Human T-Cell Lymphotropic Virus (HTLV) Types 1 or 2 are delta retroviruses that may lead to complications including adult T-cell leukemia-lymphoma (ATLL) and HTLV-1-associated myelopathy (HAM). There is concern that immunosuppression may result in progression from an asymptomatic carrier state to ATLL or HAM. Data on the safety of stem cell transplantation (SCT) in patients with HTLV-1/2 infection are lacking. The Center for International Blood and Marrow Transplant Research (CIBMTR) was queried for all patients who tested positive for HTLV infection in the pre-transplantation workup and underwent either autologous SCT (AutoSCT) or allogeneic SCT (AlloSCT) between 2008-2017. The primary outcome was overall survival up to four years post-SCT, assessed using the Kaplan-Meier statistic. All analyses were univariate and did not adjust for differences in disease, disease stage or patients characteristics. In those who underwent AutoSCT, 54 (0.5%) patients were HTLV-positive and 9,837 were HTLV-negative. In those who underwent AlloSCT, 126 (0.7%) patients were HTLV-positive and 18,084 were HTLV-negative. In the HTLV-negative group, a larger proportion underwent AlloSCT for acute myeloid leukemia in the HTLV-negative group, while Non-Hodgkin lymphoma/other leukemia was more common in the HTLV-positive group (P<0.001). Additional patient demographics are listed in Table 1. No difference in overall survival (p=0.661) or non-relapse mortality (p=0.522) was noted following AutoSCT based on HTLV status. Following AlloSCT, univariate analysis showed the HTLV-positive patients had a statistically significant lower overall survival (Figure 1; p=0.013) and higher non-relapse mortality at year four (Figure 2; p=0.023). In conclusion, survival after AutoSCT seems unaffected by HTLV status. While the underlying indications for AlloSCT differed in HTLV-infected patients, decreased overall survival and increased non-relapse mortality were seen in HTLV-positive patients. Reasons for increased non-relapse mortality may include increased infectious complications or graft-versus-host disease. Further studies are needed to understand the relative contributions of these factors.