Abstract P3-20-04: High-resolution 18F-FDG PET-CT for peri-operative margin assessment in early-stage breast cancer: Results of an ongoing clinical study
Authors: Göker Menekse 
Published: March 2022

Abstract
Introduction Successful breast-conserving surgery (BCS) entails excision of the breast tumor with an adequate amount of surrounding healthy breast tissue, such that negative resection margins are obtained. Despite efforts to obtain tumor-free margins, approximately 20% of the breast cancer patients still require reoperation. In this study, we investigate high-resolution 18F-fluoro-deoxyglucose (FDG) positron emission tomography (PET) and X-ray computed tomography (CT) for peri-operative margin assessment. Methodology Patients who were scheduled for the resection of a confirmed early-stage breast tumor (Tis, T1, or T2) were eligible to participate in this study. Approximately two hours before standard-of-care BCS, patients were intravenously injected with 4 MBq/kg 18F-FDG. The resected specimens were subsequently imaged by a preclinical micro-PET-CT system (β and X cube; Molecubes, Ghent, Belgium). After imaging, the resected specimens were sent to the pathology department for histopathological analysis. Margin status was post-hoc assessed by eight independent image evaluators (n=2 breast surgeons, n=2 nuclear medicine physicians, n=2 radiologists, and n=2 clinical scientists). Margins of the invasive component (cases with invasive ductal carcinoma and invasive lobular carcinoma, IDC and ILC) or the in situ component (DCIS) were considered, and a positive margin was defined as ink on tumor. The diagnostic performance was calculated based on the results of histopathological analysis as a gold standard. Results Thirty patients were included in the study: n=24 with IDC, n=4 with ILC, and n=2 with DCIS. This diagnostic technique permitted high-resolution PET-CT imaging of the resected breast tumors, enabling the identification of regions with high 18F-FDG uptake. The overall diagnostic accuracy was 89%, with the highest accuracy for IDC tumors (92%), followed by ILC (81%) and DCIS (69%). During this study, we also observed that image evaluators with more experience in interpreting specimen PET-CT images demonstrated higher diagnostic accuracy (data not shown). Moreover, the results of the breast surgeons were comparable with the results of imaging experts (radiologists and nuclear medicine physicians, data not shown). Conclusion The results of this interim analysis demonstrate that high-resolution 18F-FDG-PET-CT can facilitate peri-operative margin assessment during BCS. This technique achieves high diagnostic accuracy for IDC tumors, and may therefore reduce reoperation rates in the future. Results for ILC and DCIS are also promising. Optimization of specimen PET-CT imaging for these tumor types could further improve the diagnostic performance. Furthermore, we hypothesize that the diagnostic performance of specimen PET-CT image interpretation will further enhance by training and increasing experience of the image evaluators. Study registration This ongoing clinical study was registered in the www.clinicaltrials.gov database as NCT04343079.
Table: Diagnostic performance of high-resolution 18F-FDG-PET-CT specimen imaging for margin assessment in breast malignancies.tumor typediagnostic performance (%)accuracyNPVPPVspecificitysensitivityoverall (n=30)8991899382IDC (n=24)9293939684ILC (n=4)8185908875DCIS (n=2)6980756375Abbreviations: NPV, negative predicted value; PPV, positive predicted value; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; DCIS, ductal carcinoma in situ.
Citation Format: Menekse Göker. High-resolution 18F-FDG PET-CT for peri-operative margin assessment in early-stage breast cancer: Results of an ongoing clinical study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-20-04.