Abstract P3-01-08: Axillary staging after neoadjuvant chemotherapy: The comparison of surgeon performed axillary ultrasound and 18F-FDG PET/CT with pathologic status of sentinel lymph nodes in clinically node-negative breast cancer

Objective: In the era of neoadjuvant chemotherapy (NAC), the most accurate method for axillary staging is a challenge for surgeon. Sentinel lymph node biopsy (SLNB) is the recommended choice of care for axillary staging in clinically node-negative (cN0) disease. Nevertheless, the role of preoperative axillary ultrasound (AUS) or 18F-FDG PET/CT in case of cN0 patients after NAC (ycN0) is controversial. The purpose of the presented study is to assess the correlation between surgeon performed AUS and PET/CT data with SNLB results to further determine the predictive role of AUS in pathologic staging of cN0 axilla after NAC. Materials-Methods: A single institution, retrospective review of a prospectively maintained database was analyzed to identify ycN0 breast cancer patients with AUS and 18F-FDG PET/CT. All AUS studies were interpreted by a dedicated breast surgeon experienced in ultrasound, as "normal" according to the absence of specific characteristics shown to be commonly associated with metastatic involvement at diagnosis and at the date of operation. 18F-FDG PET/CT scans was termed as negative or positive due to the standardized uptake value (SUV). Patient, tumor and operative variables including age, body mass index (BMI), date of diagnosis and surgery, AUS, 18F-FDG PET/CT scans, SLNB results, and final pathology data were evaluated. Results: Of the 69 patients with cN0 axilla after NAC, SNLB was found to be positive in 37 patients (53.6%). 2 (9.5%) out of 21 patients with a normal AUS and 3 (21.4%) out of 14 patients with negative PET/CT were ultimately found to be node-positive on pathologic assessment of SLNB. Intraoperative sonography accurately identified the SLN in 92.7% of cases. The sensitivity, specificity, positive and negative predictive values were 94.5%, 59.3%, 72.9% and 90.5% for surgeon-performed AUS and 91.8%, 34.4%, 61.8% and 78.6% for PET/CT scans, respectively. Overall accuracy was found to be %78.2 for AUS and 65.2.% for PET/CT. The presence of lymphovascular invasion (LVI), micrometastasis, primary tumor size, and body mass index were found to be significantly different between true and false negative AUS. None of the clinicopathological features of the primary tumor were significantly associated with FDG uptake in the axillary lesion. Micrometastatic disease, the size and number of metastatic nodes were significantly associated with FDG uptake leading to a difference between true and false negative PET/CT for axillary disease. No significant difference was noted with regard to patient age, tumor grade, histologic type, hormone receptor status, and time between AUS or PET/CT and axillary surgery. Conclusion: Surgeon performed AUS is a beneficial tool with the potential of accurate prediction of axillary disease in up to 78% of patients after NAC. Nevertheless, the accuracy of AUS findings should be interrogated cautiously particularly for larger tumors with LVI or micrometastasis in overweight patients. Similarly, our data also imply that PET/CT had a limited value in the evaluation of axillary nodes and is not sufficient to predict axillary status particularly in case of micrometastasis after NAC. Citation Format: Karadeniz Cakmak G, Uslu R, Emre AU, Elmas O, Karadere Y, Konuk MB, Engin H, Dogan Gun B. Axillary staging after neoadjuvant chemotherapy: The comparison of surgeon performed axillary ultrasound and 18F-FDG PET/CT with pathologic status of sentinel lymph nodes in clinically node-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-01-08.