Abstract 89P
Background
Positive surgical margins for breast cancer (BC), defined as ink on tumor, occur in 20% of cases. Therefore, finding a time- and cost-effective method for intra-operative margin assessment is crucial to avoid the need for re-operation. Our study aimed to evaluate the feasibility and effectiveness of an intra-operative micro-Positron Emission Tomography - Computed Tomography (PET-CT) specimen imager for assessing margins in BC patients undergoing breast-conserving surgery.
Methods
Forty-one patients with early-stage BC were enrolled in this pilot study at Ghent University Hospital from June 2017 until June 2022. Intra-operative imaging of the specimens was performed by the ß-CUBE (micro-PET) and X-CUBE (micro-CT), later joined as one intra-operative micro-PET-CT called AURA 10 (XEOS, Ghent, Belgium). All images were interpreted at an acquisition time of 10 minutes and a 18F-FDG dose of 0.8 MBq/kg. Seven doctors, including four gynaecologists, two nuclearists and one radiologist, assessed margin status post-operative as positive, close (<1mm) or negative (no intra-operative intervention). Sensitivity and specificity were calculated by using histopathology as the golden standard.
Results
Invasive ductal carcinoma (IDC) ± ductal carcinoma in situ (DCIS) was seen in 31 patients, other types were lobular carcinoma (n=6), DCIS only (n=2) and neo-adjuvant therapy (n=2). Margin assessment of IDC ± DCIS, resulted in a mean sensitivity of 91%, specificity of 94% and accuracy of 87% (close margins were seen as positive). Positive margins of IDC on histopathology were observed in 29% (9/31) of cases. Micro-PET-CT correctly identified 8 out of 9 positive margins, and all doctors agreed on these findings (k=1). An immediate cavity shave was done in 45% (4/9) based on specimen radiography (standard of care) but 55% (5/9) still required re-operation. Notably, 16% (5/31) needed a re-operation for a positive margin that was already identified by all doctors on micro-PET-CT.
Conclusions
Our results with the micro-PET-CT specimen imager demonstrated high sensitivity and specificity for assessing tumour margins in IDC (± DCIS). This device has the potential to reduce re-operation rates more efficiently by allowing immediate and precise cavity shaves during initial surgery (NNT = 4).
Legal entity responsible for the study
Ghent University Hospital.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.