GRAPEVINE, TEXAS—The order in which patients receive cyclophosphamide (Cy) and total body irradiation (TBI) does not affect the outcome of hematopoietic stem cell transplant (HSCT), researchers have reported.
In a large, retrospective study, the rates of relapse, survival, chronic graft-vs-host disease (GVHD), and other complications were similar whether patients received Cy-TBI or TBI-Cy.
However, receiving Cy-TBI was associated with a slight decrease in the risk of grade 2-4 acute GVHD.
Jennifer L. Holter-Chakrabarty, MD, of the University of Oklahoma in Oklahoma City, presented these findings at the 2014 BMT Tandem Meetings as abstract 13.
She noted that other researchers have investigated the impact of TBI/Cy order, but the results have not provided definitive answers.
“Mouse models show that TBI-Cy is superior, with reduced lung toxicity and increased incidence of bone marrow damage,” Dr Holter-Chakrabarty said.
“Cy-TBI, however, in a retrospective study, showed improved anti-leukemic effect, as well as increased incidence of sinusoidal obstructive syndrome. So for this reason, we wanted to look at the CIBMTR database and compare the order of cyclophosphamide and TBI.”
She and her colleagues analyzed data from 1769 HSCT recipients who were younger than 60 years of age and had been reported to the CIBMTR from 2003 to 2010. Patients had been diagnosed with acute myeloid leukemia (AML, n=945) or acute lymphoblastic leukemia (ALL, n=824) and were in their first or second remission.
They had received TBI doses of at least 1200 cGy, followed by related or unrelated bone marrow or peripheral blood stem cell grafts. Patients who had received cord blood, haploidentical, or T-cell-depleted grafts were excluded.
In all, 948 patients received Cy-TBI, and 821 received TBI-Cy. The 2 cohorts had comparable patient-, disease- and transplant-related characteristics.
The sequence of TBI and Cy did not significantly affect the rates of relapse, leukemia-free survival, or overall survival. And it had no significant impact on transplant-related complications, with the exception of acute grade 2-4 GVHD.
At 100 days, the rate of grade 2-4 acute GVHD was 39% in the Cy-TBI group and 45% in the TBI-Cy group (P=0.01). But the rates of grade 3-4 acute GVHD were 16% and 15%, respectively (P=0.62).
At 100 days, the incidence of veno-occlusive disease and sinusoidal obstructive syndrome was 4% in the Cy-TBI group and 6% in the TBI-Cy group (P=0.082). At 1 year, the incidence of interstitial pneumonia syndrome was 6% and 5%, respectively (P=0.370).
At 3 years, the relapse rate was 27% in the Cy-TBI group and 29% in the TBI-Cy group (P=0.34). Leukemia-free survival was 48% and 49%, respectively (P=0.27). And overall survival was 53% and 52%, respectively (P=0.62).
Transplant-related mortality at 3 years was 24% and 23%, respectively (P=0.67). And the rate of chronic GVHD was 45% and 47%, respectively (P=0.39).
“So, in this population, we see no difference,” Dr Holter-Chakrabarty said. “Cy-TBI or TBI-Cy—it seems to not make a difference either way in relapse, treatment-related mortality, [chronic] graft-vs-host disease, acute 3 and 4 [GVHD], and survival. However, it does give us an idea that 2-4 acute GVHD may be lower in Cy-TBI.”