Abstract PS1-40: Can sentinel lymph node biopsy be avoided in patients of breast cancer with normal preoperative ultrasound of axilla

Introduction: Need for any form of surgery for axillary lymph nodes in breast cancer with clinical and radiologically negative axilla is being increasingly questioned. Randomized controlled trials are underway to answer this question. This study was undertaken to evaluate the results of sentinel node lymph biopsy (SLNB) in patients with normal preoperative axillary ultrasound (AUS) after obtaining institution ethics committee approval. Materials and Methods: All patients of operable breast cancer seen in the Breast Cancer Clinic at Sultan Qaboos University Hospital, underwent routine preoperative AUS as part of staging work up. In patients with suspicious lymph nodes, fine needle aspiration cytology (FNAC) was performed. Patients with clinical and radiologically normal axilla underwent BCS/ mastectomy with SLNB (Group 1), while patients with positive lymph nodes underwent neoadjuvant chemotherapy (NACT) and repeat AUS after completion of chemotherapy. Patients who were reported to have normal AUS post NACT underwent SLNB (Group 2). Negative Predictive Value (NPV) and probability of positive SLN when AUS was normal were calculated for the entire cohort, group 1 and group 2. A comparison of NPV between two groups was performed at a 5% level of significance (MedCalc 12.7, 2013). Results: Between 2016-2018, 165 patients with normal AUS underwent SLNB. One hundred and thirteen of these patients underwent ‘upfront’ SLNB, while 52 patients had received NACT and then underwent SLNB. Mean age of patients was 49.33 years (range: 32-74 years ) and was similar in both groups. Mean number of lymph nodes obtained was 4.7 (range 2-8) in group 1 and 4.69 (range 2-6) in group 2. Mean number of positive lymph nodes was 1.69 in group 1 and 2.4 in group 2. Out of 165 patients with normal AUS, 51 patients had metastasis in SLNs. Twenty nine of 113 patients in group 1 showed metastasis in SLNs while 22 out 52 patients in group 2 showed metastasis. NPV for AUS for the whole group was 69.1% (95% CI=62.0%-76.2%), and for group 1 & 2 were 74.3% (95%CI=66.2%-82.4%) and 57.6% (95% CI=44.2%-71.0%), respectively. A significant higher NPV was found in group 1 than in group 2 (χ2=3.873, p=0.049). Thus, the probability of positive SLN even when AUS was normal was 0.31 for whole group, 0.25 for group 1 and 0.42 for group 2. Conclusion: Probability of metastasis in SLN when AUS with or without FNAC is normal is more than 20%. Thus there is need for better preoperative imaging of axilla in patients of breast cancer with clinically and radiologically negative axilla before abandoning SLNB altogether.Citation Format: AlJarrah Adil, Seenu V, Badriya Al Qassabi, Hajar Nasser Alsaadi, Safa Abdullah Al-abadi, Srineil Vuthaluru, Moon-Fai Chan, Radiya Al Ajmi. Can sentinel lymph node biopsy be avoided in patients of breast cancer with normal preoperative ultrasound of axilla [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-40.