Clonal hematopoiesis in hematopoietic stem cell transplantation

Purpose of review Clonal hematopoiesis (CH) is characterized by the acquisition of somatic mutations and subsequent expansion of mutated hematopoietic stem and progenitor cell (HSPC) clones without clinical evidence for a hematologic neoplasm. The prevalence of CH continuously increases with age reaching double-digit percentages in individuals >60 years. CH is associated with an increased risk for hematologic neoplasms and cardiovascular disease. We will review recent efforts to investigate how CH influences patient outcomes in hematopoietic stem cell transplantation – both autologous (ASCT) and allogeneic (allo-HSCT). Recent findings Donor-engrafted CH is common in allo-HSCT recipients. Apart from a higher incidence of chronic GvHD and the rare but devastating complication of donor-derived leukemia, CH does not appear to negatively impact outcomes in allo-HSCT recipients. In lymphoma patients undergoing ASCT, however, CH is associated with an excess mortality driven by therapy-related myeloid neoplasms and cardiovascular events. Interestingly, inferior overall survival in patients with CH undergoing ASCT for multiple myeloma (MM) is due to an increased rate of MM progression. Summary CH is highly prevalent in both allo-HSCT and ASCT patients suggesting a clinically relevant but context-dependent impact on adverse outcomes. Given the current lack of therapeutic interventions, systematic screening for CH in the transplant setting is currently not indicated outside of clinical studies.