Abstract P3-13-04: 18F-FDG micro-PET/CT for intraoperative margin assessment in breast conserving surgery using: A proof-of-concept study

Positive surgical margins represent a high risk for adverse clinical outcome in breast conserving surgery (BCS). Therefore, the goal of BCS is to avoid positive margins and hence avoid reoperation. Unfortunately, most studies currently assess the rate of positive resection margins at 20%. This is in part due to the lack of a time- and cost-effective method for intraoperative margin assessment, which would enable the prediction of positive margins during the initial surgery. We propose to address this problem by performing intraoperative high-resolution 18F-fluoro-deoxyglucose (FDG) positron emission tomography (PET) with X-ray computed tomography (CT). This method relies on the high sensitivity of FDG-PET for detecting metabolically active tumor tissue, and the delineation of the anatomical margins of the specimen using CT. In this proof-of-concept study we assess the feasibility of this technique.

Twenty patients with breast cancer that were eligible to undergo BCS were enrolled in the study after providing informed consent. The study was approved by the Ethics Committee of Ghent University Hospital. Prior to surgery each patient was administered 4 MBq/kg of FDG. Surgery was performed 2-4 hours after tracer administration. Following surgical excision the breast specimen was oriented with sutures and micro-PET/CT images were obtained using the MOLECUBES β-CUBE (PET) and X-CUBE (CT). The scan time was 10 minutes on PET and 3 minutes on CT. The specimen was then sent for histopathological assessment. Micro-PET/CT images were analyzed using an automated algorithm. Briefly, this algorithm defined the contour of the tumor as the region with high FDG uptake and the contour of the specimen based on the CT image. The margin status of a specimen was positive if the distance between the contour of the tumor and specimen was 0 mm. Images were also analyzed postoperatively by two surgeons blinded to the histopathological and algorithm analysis results. The sensitivity and specificity of the proposed method were then calculated by comparing to the histopathological results, which is the gold standard for margin status assessment.

In all samples a region with high FDG uptake was visualized, which corresponded to the tumor on histopathological. In one specific case a small satellite lesion with high FDG uptake, 3 mm in diameter, was detected on the micro-PET images at a distance from the main tumor. Histopathological confirmed that this previously undetected lesion was a second invasive carcinoma. For margin status, a sensitivity of 75% and specificity of 75% were obtained using automated algorithm analysis. Sensitivity and specificity obtained based on surgeons' analysis was 62,5% and 75% for surgeon A and 87,5% and 91,7% for surgeon B respectively. Taking into account the intra-operative micro-PET results could theoretically have reduced the reoperation rate by 75%.

This proof-of-concept study demonstrates that high-resolution intraoperative FDG-PET/CT is a promising technique for intraoperative margin assessment in BCS that could allow to reduce re-excision rate. This technique achieves both sufficient sensitivity and specificity with minimal disruption of intraoperative workflow.

Citation Format: Marcinkowski R, Keereman V, Van Holen R, Vandenberghe S, Van Bockstal M, Van Dorpe J, Brans B, Goker M, Depypere H, Van den Broecke R. 18F-FDG micro-PET/CT for intraoperative margin assessment in breast conserving surgery using: A proof-of-concept study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-13-04.