In order to improve accrual to a randomized clinical trial of double unrelated cord blood (dUCB) versus HLA-haploidentical bone marrow (Haplo-BM) transplantation, patients with less prior therapy and potentially greater immunocompetence were enrolled. In order to reduce the risk of graft rejection, patients randomized to receive dUCB received a higher dose of total body irradiation (TBI) (300 vs. 200 centiGray [cGy]).
Determine whether inclusion of recipients of 300 cGy TBI influenced the trial outcomes.
This was a secondary analysis of dUCB recipients: 161 received TBI 200 cGy and 18 received TBI 300 cGy. Fine and Gray regression was used to evaluate the effect of TBI dose on relapse and non-relapse mortality (NRM). Cox regression was used for neutrophil engraftment and overall survival.
Patient characteristics were similar in both TBI dose subgroups. The probability of neutrophil engraftment was 100% for patients who received TBI 300 cGy vs. 91% (95%CI, 86-95%) with TBI 200 cGy (p=0.64), which was similar after regression analysis adjusting for age, total infused nucleated cell dose, HLA matching to the patient, and comorbidity score. We also investigated whether the lower survival probability and higher cumulative incidence of NRM observed in the dUCB arm of BMT CTN 1101 could be influenced by the TBI 300 cGy patient subset. There was no significant difference in the 1-year incidences of NRM and relapse, nor in 1-year survival, even after adjusting in multivariate analysis.
Patients in BMT CTN 1101 who received TBI 300 cGy and 200 cGy had similar engraftment and early mortality. We conclude that inclusion of a modified regimen for dUCB transplantation had no demonstrable influence on this large randomized trial.

Copyright © 2021. Published by Elsevier Inc.