Axillary assessment by Systemic Axillary Sonography (SAS) for axillary disease treated with neoadjuvant chemotherapy

Abstract Objective. For patients with breast cancer related lymph node metastases, neoadjuvant chemotherapy (NAC) can de-escalate axillary surgery. A radiologic marker (RM) is commonly placed at the time of the initial biopsy to ensure removal of that node at final surgery, but the utility of this marker is largely debated. Systematic Axillary Sonography (SAS) consists of a thorough sonographic axillary staging before and after NAC with possible post NAC node biopsy and has been previously suggested as an alternative. The primary aim of this study was to assess the effectiveness of SAS in axillary evaluation after NAC. The secondary aim was to compare the effectiveness of SAS to RM. Methods. A retrospective analysis of prospectively collected data from 95 patients from 2010 to 2020 at University of Miami Hospital and Jackson Memorial Hospital. Study inclusion criteria were positive axillary lymph node (LN) biopsy, NAC, performance of SAS and axillary surgery. Results. 89 patients were analyzable. The median age was 49±12. All patients had clinical axillary exam and axillary US with positive LN biopsy. 62 patients had additional breast MRI before treatment. All patients had clinical axillary exam and axillary US after chemotherapy. 58 patients had post-treatment MRI and 49 repeated axillary LN biopsy. Pre-treatment clinical exam of the axilla had a sensitivity of 73%. When MRI was added the sensitivity rose to 95%. Since axillary US and positive axillary node biopsy were a prerequisite, the sensitivity of pre-NAC US cannot be assessed. After chemotherapy, all patient underwent axillary examination and US assessment. Repeated axillary clinical exam had low sensitivity of 31% and high specificity of 85%. Repeat MRI exam showed low sensitivity and specificity of 53% and 49% respectively. Post-NAC US without subsequent LN biopsy had a sensitivity of 55% with specificity of 67%. The addition of repeat axillary LN biopsy increased the sensitivity of SAS to 100%. 59 patients in our group had RM placed during pre-NAC axillary LN biopsy. 24 underwent axillary dissection without sentinel lymph node biopsy (SLNB) and 35 patients had a SLNB. The RM was retrieved in 32/35 patients. The “clipped” node was also sentinel node in 66% (12/35). The final pathology revealed benign results in all “clipped” non-sentinel nodes. 18% (6/33) of patients with “clipped” node were diagnosed with axillary metastases in “non-clipped” lymph nodes. Conclusion. SAS is a cheap, quick and reliable method facilitating pre and post-treatment assessment and restaging of the axilla after NAC. Post-NAC biopsy, when indicated, better defines eligibility for axillary surgery decreasing morbidity and cost. In this study, placement of a RM was of no significant benefit. Patient characteristicsRaceTumor gradeWhite, non-hispanic19Gr 13White-hispanic46Gr 240Black, non-hispanic18Gr 346Asian3Receptor statusUnknown3HR+/HER2-42Age49+/-12HR+/HER2+19BMI29+/-5.7HR-/HER2+7Menopausal statusHR-/HER2-21Premenopausal49Tumor sizePostmenopausal40T19T238T328T414LN statusN158N221N310 Citation Format: Siarhei Melnikau, Christina Layton, Tolga Ozmen, Megan Allen, Eli Avisar. Axillary assessment by Systemic Axillary Sonography (SAS) for axillary disease treated with neoadjuvant chemotherapy [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 P1-01-14.