Hematopoietic stem cell transplantation (HSCT) may offer the chance of a cure for patients with leukemia and other blood cancers, but the process of preparing the body to receive such a transplant can be brutal, involving whole body irradiation as well as chemotherapy conditioning. New results show that both steps are needed: a trial that omitted whole body irradiation in young patients with acute lymphoblastic leukemia (ALL) was stopped early because of significantly poorer outcomes.
The multicenter, global FORUM (For Omitting Radiation Under Majority Age) trial involved 75 centers in 17 countries between 2013 and 2018.
“Our study shows significantly better outcomes for total body irradiation compared to myeloablative chemo-conditioning arms, with no differences between the [two] chemo-conditioning groups,” concluded Christina Peters, MD, professor of pediatrics in the department of stem cell transplantation at St Anna Children’s Hospital in Vienna.
, she added.
Dr. Peters presented the findings as part of the virtual annual congress of the European Hematology Association.
Describing the results as “sobering,” session comoderator Shai Izraeli, MD, director of the department of hematology-oncology at Schneider Children’s Medical Center, in Petah Tikva, Israel, said an online comment from the virtual meeting audience reflected the reaction to these unwelcome results: “So we are still stuck with total body irradiation?”
Dr. Peters said the good news is that the number of patients needing to undergo stem cell transplants is low, and with research advances, may hopefully drop even further.
“Only 10% of patients under the age of 18 nowadays undergo allogeneic HSCT, and perhaps in the future that will become even less if we are able to rescue some of the groups with other immunological measures such as CAR-T cells and antibodies,” she said.
“I think it is very important to better identify those who really need total body irradiation in the future,” she added.
In an interview, Dr. Izraeli agreed.
“The prognosis of children after bone marrow transplantation is excellent – the majority are cured from their leukemia,” he said. “And we have to remember that those who undergo bone marrow transplant have the worst leukemias.”
He pointed out that, in fact, contemporary chemotherapy alone is effective in the treatment of more than 90% of patients with ALL younger than aged 18.
For the 10% of patients who do not respond to chemotherapy alone and undergo allogeneic HSCT, about 50%-80% of pediatric patients who have resistant leukemia are cured. However, the total body irradiation used to prepare the body to receive the transplant is linked to potentially serious consequences later in life, including sterility, lung problems, growth retardation, and secondary cancer.
To determine if the irradiation component could be safely replaced with a chemotherapy-based conditioning approach, Dr. Peters and colleagues conducted the FORUM trial.
In total 413 patients undergoing HSCT were enrolled and randomized to pretransplant conditioning with total body irradiation and etoposide (n = 202) or a chemotherapy-only approach with fludarabine/thiotepa/busulfan (flu/thio/bu; n = 99) or fludarabine/thiotepa/treosulfan (treo; n = 93).
Most patients (72%) had B-cell precursor ALL and 23% had T-cell ALL. Just over half (54%) were transplanted in first complete remission (CR1), 40% in CR2, and 4% in CR3.
The source of stem cells was bone marrow for most patients (82%); peripheral blood stem cell for 12%, and cord blood for 4%.