Radiation dose homogeneity in an EORTC multicenter trial on breast irradiation

The influence of the radiation dose on local control and cosmetic outcome in breast-conserving treatment for breast cancer is investigated in EORTC trial 2288110882. In this study 50 Gy is administered to the whole breast, and the effect of an additional dose to the tumor-bearing area (boost dose) is evaluated. The purpose of this analysis is to document the dose homogeneity of the radiation dose as reported in the first 1915 treatment forms, received at the EORTC Data Center. The dose to the prescription Point (A) was within 95 and 110% of 50 Gy in all but 13 (99.3%) patients (median dose 50 Gy) and the minimum and maximum doses in the central plane of the breast were within 95% and 110% of the dose to point A in 82% of patients. The dose to the tumor excision area (point B) was within the homogeneity criteria in 97% of patients, and the boost doses were consistent with randomization in 93% of cases. These data, based on one-third of the randomized patients in trial 22881/10882, demonstrate a high level of homogeneity in radiation doses, despite a number of ambiguities in the protocol, which were efficiently clarified a few months after the beginning of the trial. This high level of consistency is a remarkable achievement given the number of centers, the number of patients, and the number of countries involved in this trial.