[Assessing the contribution of a standardized method in defining the tumor bed using surgical clips in breast cancer]

The objective of this study was to compare prospectively the delineations of tumour bed after breast conserving surgery from two techniques for defining the target volume.

Sixteen patients treated by lumpectomy with development of surgical clips were included. For each patient, four radiation oncologists delineated the clinical target volume (CTV boost) following its own method (technique 1) or using a predefined methodology (technique 2), the diameter to be applied around each clip relative to the risk of local recurrence. Factors taken into account to adjust the volume were tumour size, age, surgical margins and the presence of extensive ductal carcinoma. We then analyzed the factors varying the volume and variation of delineation for each method by calculating the concordance index: Kappa index and overlap.

For all 16 patients, the volume delineated was nearly identical: 29.65 cm(3) with technique 1 and 33.54 cm(3) with technique 2 (P=0.6). The correlation was higher with technique 2 over technique 1, with KI from 0.146 to 0.285 (P=0.0001) and an OV of 0.302 to 0.458 (P=0.0002).

Our study shows that within the same institute, there is a great variability in CTV delineation boost, even in the presence of surgical clips. A standardized approach to adjusting the volume of relapse risk factors has improved the consistency.