Does preoperative positron emission tomography help delineate the boost volume after oncoplastic surgery for breast cancer?

Abstract

OBJECTIVE The tumor bed within the breast shifts during oncoplastic surgery (OPS) for breast cancer (BC). Preoperative imagery is used to determine the boost volume (BV) for patients not implanted with surgical clips. This prospective study was conducted to geometrically compare BVs determined using preoperative imagery and BVs determined utilizing surgical clips. METHODS Patients diagnosed with BC were scanned using PET-CT during 2013-2015. Twenty patients who had undergone OPS but who did not have metastasis underwent CT prior to radiotherapy. Their preoperative images were fused with planning CT images. The tumor volume (CTVboost-pet), as determined from the preoperative PET-CT images, was contoured. Next, CTVboost-clips was determined using surgical clips. Geometric relationships between these two volumes were statistically compared. RESULTS Planar projections of CTVboost-pet and CTVboost-clips were evaluated. Displacements between CTVboost-pet and CTVboost-clips in the axial (XZ) and coronal (XY) planes were 1.17 cm (min-max: 0.03-3.64 cm) and 1.67 cm (min-max: 0.38-4.14 cm), respectively, and were statistically significant (p<0.001), whereas the displacement in the sagittal (YZ) plane was 1.07 cm (min-max: 0.04-4.45 cm) and was not significant (p>0.7). CONCLUSION Preoperative imaging alone was not reliable when determining the BV in patients who had undergone OPS and had no clips. Large PTV margins can be an option to overcome this issue. Surgical clips need to be inserted during OPS.