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Myeloablative conditioning prolongs RFS for AML, myelodysplastic syndrome
Myeloablative conditioning conferred longer RFS than reduced-intensity conditioning among patients with acute myeloid leukemia or myelodysplastic syndrome, according to results of a phase 3 clinical trial.
Researchers also observed longer OS with myeloablative conditioning than reduced-intensity conditioning; however, this was not statistically significant due to a lower-than-expected rate of treatment-related mortality.
“Our trial strongly supports that patients aged [younger than] 65 years with acceptable hematopoietic stem cell transplantation comorbidity index scores should receive myeloablative conditioning,” Bart L. Scott, MD, assistant member of the transplant program at Fred Hutchinson Cancer Research Center in Seattle, and director of hematology and hematologic malignancies at Seattle Cancer Care Alliance, and colleagues wrote.
Scott and colleagues of the Blood and Marrow Transplant Clinical Trials Network randomly assigned 272 adults with AML or myelodysplastic syndrome to a treatment regimen with myeloablative conditioning (n = 135) or reduced-intensity conditioning (n = 137) followed by first HSCT.
Each patient had an HSCT comorbidity index less than four and less than 5% marrow myeloblasts before HSCT.
OS measured 18 months after random assignment based on intent-to-treat analysis, served as the primary endpoint.
At 18 months, OS was higher in patients who received myeloablative conditioning (77.5%; 95% CI, 69.4-83.7) than in patients who received reduced-intensity conditioning (67.7%; 95% CI, 59.1-74.9). However, the point difference did not reach statistical significance (9.8%; 95% CI, –0.8 to 20.3).
Researchers saw no significant improvement in 18-month OS with myeloablative compared with reduced-intensity conditioning when separately evaluating patients with AML (76.4% vs. 63.4%) and myelodysplastic syndrome (81.5% vs. 85.2%).
A greater proportion of patients who received reduced-intensity conditioning experienced relapse (48.3% vs. 13.5%; P < .001); based on these data, the trial ended accrual at 272 of 356 expected patients.
RFS at 18 months was 67.8% (95% CI, 59.1-75) in patients treated with myeloablative conditioning compared with 47.3% (95% CI, 38.7-55.4) in patients treated with reduced-intensity conditioning (P < .01).
Treatment-related mortality occurred in 4.4% (95% CI, 1.8-8.9) of patients who received reduced-intensity conditioning compared with 15.8% (95% CI, 10.2-22.5) of patients who received myeloablative conditioning (P = .002).
The most common adverse events were mucositis and abnormal liver function with myeloablative conditioning and abnormal liver function and dyspnea with reduced-intensity conditioning.
Researchers observed higher rates of the cumulative incidence of grade 2 to grade 4 graft-versus-host disease at day 100 (44.7% vs. 31.6%; P = .024) and 18 months (64% vs. 47.6%; P = .019) with myeloablative conditioning.
“Patients who are not candidates for myeloablative conditioning should be considered for novel regimens that exploit enhanced antimyeloid activity through chemotherapy, immunotherapy or biologically targeted mechanisms,” the researchers wrote. “Myeloablative conditioning remains the standard of care for patients undergoing HSCT for AML or myelodysplastic syndrome.” – by Melinda Stevens
Disclosures: Scott reports no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.