Impact of drug development on the use of stem cell transplantation: a report by the European Society for Blood and Marrow Transplantation (EBMT)

Hematopoietic stem cell transplantation (HSCT) is used with increasing frequency in Europe with 40 000 transplants reported in 2014. Transplant-related mortality remains high in allogeneic HSCT (10-20%); high-dose chemotherapy is toxic and demanding for patients. Drug development is accelerating and with limited toxicity of some targeted drugs may replace HSCT, whereas others may function as a 'bridge to transplant'. We analyzed HSCT reported to the activity survey for selected diseases in which major advances in drug development have been made. Tyrosine kinase inhibitors markedly changed the number of allogeneic HSCT in early CML. In myelodysplastic syndromes, hypomethylating agents show no effect on HSCT activity and Janus kinase inhibitors for myeloproliferative neoplasm appear to have only a temporary effect. For CLL autologous HSCT decreased after publication of trials showing improved PFS but no overall survival advantage and allogeneic rates are dropping after the introduction of Bruton kinase and PI3K Inhibitors. Whether these are 'game changers' as was imatinib for CML requires additional follow-up. For myeloma, proteasome inhibitors and new immunomodulatory drugs do not appear to impact transplant rates. Drug development data show different effects on HSCT use; highly effective drugs may replace HSCT, whereas other drugs may improve the patient's condition to allow for HSCT.