Specimen PET-CT Imaging for Intraoperative Margin Assessment in Early-Stage Breast Cancer

Importance: Positive margins occur in 12% to 30% of breast-conserving surgeries and are associated with increased local recurrence risks. Accurate and efficient intraoperative margin assessment, therefore, remains an unmet clinical need. Objective: To evaluate the success rate of intraoperative specimen positron emission tomography (PET)-computed tomography (CT) imaging in addressing positive margins in patients with invasive ductal carcinoma. Design, Setting, and Participants: This was an interventional, multicenter, nonrandomized clinical trial that recruited patients from June 2022 to March 2025. Patients were followed up 2 weeks after surgery. Six European breast cancer centers participated and integrated specimen PET-CT imaging into their routine surgical flow. The analysis included eligible patients with early-stage breast cancer scheduled for breast-conserving surgery. Interventions: Patients received an intravenous injection of low-dose 18F-fluorodeoxyglucose (FDG; 0.8 MBq/kg). After tumor excision, the specimen was imaged intraoperatively using a dedicated specimen PET-CT scanner. Surgeons interpreted PET-CT images intraoperatively, and additional tissue was excised when margins were deemed suspicious to achieve final negative margins. Main Outcomes and Measures: The primary outcome was the success rate of specimen PET-CT in addressing positive margins for the invasive component in patients undergoing breast-conserving surgery for invasive ductal carcinoma. Secondary outcomes included success rates in other breast cancer subtypes, final positive margin rates, reoperation rates, and diagnostic performance using histopathology as the reference standard. Results: The analysis cohort consisted of 148 female patients with a median (IQR) age of 65 (53-73) years and a median (IQR) preoperative tumor size of 17 (12-22) mm. For the invasive component of invasive ductal carcinoma, success rates increased from 83.3% (70 of 84 patients) without intraoperative margin assessment (IMA) to 86.9% (73 of 84 patients) with routine margin assessment and to 95.2% (80 of 84 patients) with specimen PET-CT (P < .001 vs no IMA). Across all study groups, success rates improved from 76.4% (113 of 148 patients) without IMA to 81.8% (121 of 148 patients) with routine margin assessment techniques and to 91.9% (136 of 148 patients) with specimen PET-CT (P < .001 vs no IMA; P = .009 vs standard-of-care IMA). Conclusions and Relevance: Study findings show that specimen PET-CT imaging was associated with an improvement in the assessment of positive margins for invasive component in patients undergoing conserving surgery for early breast cancer. The use of this integrated approach might lead to a substantial reduction of re-excision rates after breast-conserving surgery. Trial Registration: ClinicalTrials.gov Identifier: NCT04999917.