Henry Chi Hang Fung, MD, FACP, FRCPE
Nearly 50 years after the first successful bone-marrow transplant to treat leukemia, the number of hematopoietic stem cell transplants (SCTs) performed annually continues to increase. Growth will continue in the coming years, predict experts in the field.
Questions about the future of cell transplantation programs “have been asked over the past 30 or 40 years, and transplant is still here,” Fung said. “The field has evolved rapidly. For example, the cellular therapies—CAR T-cells or engineered T-cells—are rapidly expanding, and they’re always done by transplant programs. FDA will only let transplant people do them. Transplant will be rapidly expanding, depending on how you define it.”
Expanded Donor-Cell Options
Traditional SCT falls into 2 categories: autologous and allogeneic. In the autologous variety, a patient’s blood-forming stem cells are collected, chemotherapy is administered, and the cells are reinfused into the patient. Autologous SCT is a standard treatment for multiple myeloma (MM), which accounts for the largest number of transplants overall. Autologous is also the predominant type used to treat non-Hodgkin lymphoma (NHL) and Hodgkin disease.1
“Probably the biggest change in the last 5 years has been the use of half-matched donors or haploidentical stem cell transplant,” said John F. DiPersio, MD, PhD, a professor at Washington University School of Medicine in St. Louis, Missouri. “They’ve emerged onto the scene robustly and the numbers of haplo transplants are increasing. Most studies show that the outcomes are fairly similar to unrelated donor transplants. Now it’s conceivable that you can find a donor for nearly everyone, which was not the case in the past. We’ve seen this emerge and the growth of unrelated donor transplants has slowed.”
Figure 1. Allogeneic SCT Recipients in the United States by Donor Type1
Trends in Stem Cell Sources
An earlier major innovation in the 1980s and 1990s was the development of methods to harvest stem cells from blood rather than bone marrow. Peripheral blood stem cell (PBSC) transplantation is now standard in autologous transplant and is used in more than 75% of allogeneic SCTs.2
PBSCs are easier to collect and produce faster engraftment, although they are associated with higher rates of chronic GVHD, which is of particular concern for pediatric patients who will live for many decades after treatment.
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