Outcomes of Allogeneic Haematopoietic Transplant for Chronic Lymphocytic Leukaemia in the Modern Era

Abstract There is limited data on the use and outcomes of allogeneic haematopoietic stem cell transplant (HSCT) in the modern era of chronic lymphocytic leukaemia (CLL) treatment. The aim of this study was to examine CLL transplant outcomes with a focus on patients exposed to pathway inhibitors (PI) prior to transplant. Data was collected through the Australian and New Zealand Transplant and Cellular Therapy Registry for all patients who underwent HSCT for CLL between 01/2009-12/2018. Transplant outcomes were compared between 2009-2013 (n=94) and 2014-2018 (n=50). There was a significant reduction in non-relapse mortality (NRM) from 42% (95%CI 31-52%) to 23% (95% CI 12-35%, p=0.02) between the periods however overall survival (OS), progression free survival and relapse were unchanged. Within the 2014-2018 cohort there was no difference in baseline characteristics between PI exposed (n=22) and naïve patients however 3-year OS was inferior in PI exposed patients: 54% (95%CI 35-82) compared to 91% (95%CI 80-100; p=0.03). In multivariate analysis, complete remission at the time of HSCT was associated with improved OS (hazard ratio [HR] 2.54, 95%CI 1.04-6.18). Allogeneic HSCT remains a viable treatment option for selected patients with CLL however the finding of inferior OS in PI exposed patients requires further study.