Study stopped early
The aim of the study was to demonstrate noninferiority with the chemotherapy approach.
However, the significantly inferior outcome observed in the chemotherapy-only group led to randomization being halted in March 2019.
The 2-year overall survival in the intent-to-treat (ITT) analysis, with a mean observation time of 2.1 years, was 0.75 ± 0.04 for chemo-conditioning versus 0.91 ± 0.02 for total body irradiation/etoposide (ITT P < .001).
The ITT analysis showed relapses were significantly higher in the chemo-conditioning group (2-year cumulative incidence of relapse [CIR], 0.33) compared with the total body irradiation group (CIR, 0.12; P < .001).
The 2-year event-free survival (EFS) rate was also significantly higher in the total body irradiation group (0.86 vs 0.58; P < .001), and transplant-related mortality over 2 years was lower with total body irradiation (0.02 vs 0.09; P = .02).
A per-protocol analysis showed the 2-year overall survival to be the same in the two chemotherapy groups (both 0.77 ± 0.05) compared with 0.91 ± 0.02 in the total body irradiation group (P = .003).
“In this cohort [the 91% overall survival rate] may even be lower than contemporary intensive frontline therapy results that are achieved nowadays,” Dr. Peters said.
In looking at subgroups, there were no significant differences according to age group or cancer phenotype, while MLL rearrangement was associated with higher relapse incidence.
Remission status was found to notably influence EFS, dropping from 0.91 in CR1 patients with total body irradiation to 0.76 in CR2 patients. However, total body irradiation remained significantly higher compared with the chemo-conditioning groups in CR1 (P = .004) and CR2 (P < .001).
Transplant-related mortality was not significantly different between the total body irradiation and chemo-conditioning groups in the CR1 or CR2 groups (P = .09 and P = .18, respectively), despite the significant difference when remission status was not included.
Overall, “we tried to identify subgroups in which total body irradiation might be eliminated, however in all analyses, total body irradiation was better than chemo-conditioning in all arms,” Dr. Peters said.
Meanwhile, the findings underscore that even when patients cannot receive total body irradiation, the alternative chemo-conditioning therapy in fact shows favorable efficacy on its own, Dr. Izraeli said.
“The prognosis of the chemotherapy group is also quite remarkably good, although less than the total body irradiation arm. This means that if for some reason total body irradiation cannot be given, the chemotherapy is a very reasonable alternative.”
Dr. Peters has reported relationships with Amgen, Novartis, Pfizer, Medac, Jazz, and Neovii. Dr. Izraeli has reported no relevant financial relationships.
SOURCE: EHA Congress. Abstract S102.
A version of this article originally appeared on Medscape.com.