Allogeneic transplantation for adult T‐cell leukemia/lymphoma in adolescent and young adults and young patients: A nationwide retrospective study by the ATL working group of the Japan society for transplantation and cellular therapy

Abstract Allogeneic hematopoietic stem cell transplantation (allo‐HSCT) provides durable remission for patients with adult T‐cell leukemia/lymphoma (ATL); however, few studies have focused on post‐transplant outcomes in ATL patients ≤49 years. To clarify prognostic factors in ATL among patients <40 years (adolescents and young adult [AYA]; n = 73) and 40–49 years (Young; n = 330), we conducted a nationwide retrospective study. Estimated 3‐year overall survival (OS) rates were 61.8% and 43.1% in AYA and Young patients, respectively ( p = 0.005). In the multivariate analysis, Young patients showed worse OS (Hazard ratio (HR) [95% confidential interval] 1.62 [1.10–2.39], p = 0.015), chronic graft‐versus‐host disease (GVHD)‐free and relapse‐free survival (CRFS) (HR 1.54 [1.10–2.14], p = 0.011), and GVHD‐free and relapse‐free survival (GRFS) (HR 1.40 [1.04–1.88], p = 0.026) than AYA patients. No significant differences were observed in OS, CRFS, or GRFS between the myeloablative conditioning (MAC) and reduced‐intensity conditioning (RIC) regimens; however, non‐relapse mortality was significantly lower in patients with the RIC regimen than those with the MAC regimen (HR 0.46 [0.24–0.86], p = 0.015). In summary, OS was worse in Young patients than in AYA patients in the allo‐HSCT setting for ATL. Furthermore, the RIC regimen has potential as an alternative treatment option for ATL patients ≤49 years.