Abstract PS2-05-28: High-resolution specimen PET-CT imaging for intraoperative margin assessment in early-stage breast cancer: the multicenter BrIMA study

Abstract Goals: Approximately 12-30% of patients with breast cancer undergoing breast-conserving surgery (BCS) require additional surgery due to positive margins, delaying adjuvant therapy and increasing local recurrence risk. Therefore, finding a time- and cost-effective method for intraoperative margin assessment (IMA) is crucial to avoid reoperation. The prospective, multicenter, interventional BrIMA study evaluated the clinical value of intraoperatively addressing positive margins by specimen PET-CT imaging. Methods: Patients received a preoperative intravenous low-dose radiotracer injection (18F-FDG; 0.8 MBq/kg) at the nuclear medicine department and were subsequently transported to the operating room (OR). Immediately after tumor excision, the breast specimen was imaged in the OR using a compact and mobile high-resolution specimen PET-CT imager (AURA10 PET-CT, XEOS, Belgium). The operating surgeon evaluated the 3D PET-CT images during BCS. When positive margins were suspected on imaging, additional breast tissue had to be excised to achieve final negative margins (i.e. oriented cavity shaving). Routine IMA methods (e.g. specimen X-ray, gross pathology, specimen ultrasound, palpation) were permitted only after PET-CT image interpretation was completed. All specimens were then sent to the pathology department for routine histopathological evaluation. The clinical value of intraoperative specimen PET-CT imaging was quantified by the success rate. Surgery was considered successful when all margins of the main specimen were negative, or when positive margins were adequately addressed during BCS; whereas failure was defined as positive margins not addressed during BCS. Histopathology served as the gold standard. Results: The BrIMA study was conducted in six European breast centers. A total of 148 study patients were found eligible for analysis. The final analysis cohort consisted of patients with Invasive Ductal Carcinoma (IDC; n=84), IDC with preoperative aromatase inhibitor therapy (IDC-AI; n=15), IDC with neoadjuvant chemotherapy (NAT; n=13), Invasive Lobular Carcinoma (ILC; n=16), ILC with preoperative aromatase inhibitor therapy (ILC-AI; n=7) and Ductal Carcinoma In Situ (DCIS; n=13). Specimen PET-CT imaging visualized breast tumors across all subtypes, including less 18F-FDG-avid lesions (i.e. ILC, DCIS) and tumors from patient treated with neoadjuvant therapy. Resection margins were evaluable in all tumor specimens (148/148) during BCS. Across all study groups, considering both the invasive and the in situ component, the success rate improved from 76.4% (113/148) without IMA to 81.8% (121/148; p = 0.004) with the routine IMA technique and to 91.9% (136/148; p 0.001) with specimen PET-CT imaging. For the invasive component of IDC, the success rate in addressing positive margins increased from 83.3% (70/84) without IMA to 86.9% (73/84; p = 0.125) with the hospital’s routine IMA technique and to 95.2% (80/84; p 0.001) with specimen PET-CT imaging. Fifteen patients (15/148; 10.1%) required reoperation due to final positive margins. Five of these patients had positive margins in the cavity shaves, which were not assessed by specimen PET-CT imaging per study protocol and one patient required reoperation due to postoperative MRI findings. The other nine patients that underwent reoperation could be attributed to the failure of obtaining final negative margins (9/148; 6.1%). For these cases the positive margin of the main tumor specimen was neither addressed by intraoperative specimen PET-CT imaging, nor by the routine IMA methods. Conclusions: Specimen PET-CT imaging provides reliable intraoperative visualization across breast cancer subtypes and outperforms routine IMA methods, yielding clinically relevant improvements in margin assessment during BCS. Citation Format: M. Göker, O. Gentilini, G. Vergauwen, H. Markus, S. Kümmel, G. Cisternino, B. Lambert, X. Kraemer, M. Vanhoeij, V. Vergucht, R. Di Micco. High-resolution specimen PET-CT imaging for intraoperative margin assessment in early-stage breast cancer: the multicenter BrIMA study abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-05-28.