Human T-Cell Lymphotropic Virus Types 1 and 2 (HTLV-1/2) are delta retroviruses. HTLV-1 may lead to complications including adult T-cell leukemia-lymphoma (ATLL) and HTLV-1-associated myelopathy (HAM). Immunosuppression may result in progression from an asymptomatic carrier state to ATLL. 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) research database was queried for patients who tested positive for HTLV infection in the pre-transplantation workup and underwent either autologous SCT (AutoSCT) or allogeneic SCT (AlloSCT). Patients were excluded if they underwent SCT for ATLL. The primary outcome was overall survival at three and four years post-SCT. In those who underwent AutoSCT, 54 patients were HTLV-positive and 9,836 were HTLV-negative. In those who underwent AlloSCT, 105 patients were HTLV-positive and 18,077 were HTLV-negative. No difference in overall survival was noted in HTLV-positive patients vs HTLV-negative patients at three years following AutoSCT (76% vs 77%; p=0.916). Inferior overall survival (32% vs 46%; p=0.017) and non-relapse mortality (35% vs 27%; p=0.030) were observed in HTLV-positive patients at four years following AlloSCT. Future work should examine the mechanism by which HTLV-1/2 impact survival in AlloSCT recipients.
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