Siavash Atrchian - MD Department of Radiation Oncology, BC Cancer Agency, University of British Columbia
Pejman Sadeghi - MD Department of Surgery, Dalhousie University
Wladyslawa Cwajna - MD Department of Radiation Oncology, Nova Scotia Cancer Center, Dalhousie University
Lucy Helyer - MD Department of Surgery, Dalhousie University

Background: Delineation of lumpectomy cavity for whole breast radiation therapy (WBRT) after breast conserving surgery can be challenging due to poor visualization of the cavity. The use of surgical clips on lumpectomy cavity walls has been suggested as an effective and low cost method to improve the accuracy and consistency of lumpectomy cavity delineation. Methods and Materials: Twenty-three eligible female breast cancer patients who were treated with lumpectomy and adjuvant radiation therapy were recruited for this study.During breast conserving surgery, four surgical clips were placed on the superior, inferior,lateral and medial walls of the lumpectomy cavity. Patients were imaged prior and during radiation treatment. Software was developed to anonymize the image sets and digitally remove the clips from the CT images. Three radiation oncologists contoured the lumpectomy cavity volume, with and without presence of clips. Contoured image sets were analyzed with regard to cavity volume, dimensions and concordance index Statistical analysis was performed using a paired t-test.Results: The presence of clips significantly increased the average lumpectomy cavity volumes from 23.50 cc to 26.42 cc (p < 0.0001). The presence of clips also significantly increased the mean Cranio-Caudal (CC), Antero-Posterior (AP), and Medio-Lateral (ML) dimensions by 6.8 mm, 2.3 mm and 2.9 mm, respectively (all p < 0.01). Additionally, the presence of surgical clips improved the consistency in delineation in CC dimension by significantly decreasing the standard deviation (p < 0.006). Conclusions: The presence of surgical clips improves consistency of lumpectomy cavity delineation and also influences average delineated cavity volume and dimensions