Abstract PD2-04: Enhanced pre-operative axillary staging using intradermal microbubbles and contrast-enhanced ultrasound (CEUS) to identify and biopsy sentinel lymph nodes (SLN) in breast cancer is a reproducible technique and may characterise a group of patients who can completely avoid axillary surgery

Purpose In patients with breast cancer, avoiding overtreatment of the axilla without compromising oncological outcomes is an important clinical goal. Previous work has suggested that patients with a normal grey-scale ultrasound and benign radiological core biopsy of SLN identified with CEUS are unlikely to have high volume axillary metastases. We therefore assessed the reproducibility of this biopsy technique in multiple centres and in 2 centres, measured the volume of axillary metastases at the end of primary surgical treatment in patients with a false negative SLN core biopsy. Materials and Methods Between 2010 and 2016 data were collected on patients with early breast cancer; 1361 from Maidstone Breast Clinic (1) (prospective, sequential), 376 from Tunbridge Wells Breast Clinic (2) (retrospective, sequential), 122 from Leeds Breast Clinic (3) (retrospective, selected) and 48 from Imperial College Healthcare (4) (prospective, selected). Patients at Centres 1 and 2 had a normal grey-scale axillary ultrasound. Patients had a CEUS SLN core biopsy procedure prior to axillary surgery (sentinel lymph node excision (SLNE)/axillary lymph node dissection (ALND)). Results SLN were successfully core biopsied (nodal tissue retrieved) in 80% (Centre 1), 79.5% (Centre 2), 77.5% (Centre 3) and 88% (Centre 4). Patients with invasive breast cancer and a successful SLN core biopsy went on to have primary surgical treatment, 816 (Centre 1), 215 (Centre 2), 80 (Centre 3) and 38 (Centre 4). As a test to identify all SLN metastases, the sensitivities were 47.5% (95% CI 39.9-55.1), 52.5% (95% CI 39.1-65.7), 46.4% (95% CI 27.5-66.1) and 45.5% (95% CI 16.7-76.6) respectively. Specificities; 99.7% (95% CI 98.9-100), 98.1 (95% CI 94.5-99.6), 100% (95% CI 93.2-100%) and 96.3% (95% CI 81-99.9) respectively. Negative predictive values; 87.3% (95% CI 84.6-89.6), 84.5% (95% CI 78.4-89.5), 86.9% (95% CI 82.4-90.3) and 86.2% (95% CI 78.4-91.5) respectively. At Centres 1 and 2, 13/637 (2%) and 6/183 (3%) respectively of patients with a benign microbubble/ CEUS SLN core biopsy had 2 or more LN macrometastases found at SLNE/ ALND. Conclusion The identification and biopsy of SLN using CEUS is a reproducible technique. Despite the low sensitivity, the negative predictive value is high and in a large cohort of patients from centres 1 and 2, only a small proportion of patients had 2 or more 2 lymph node macro metastases that were both occult on grey-scale ultrasound and missed by SLN core biopsy. In the era of axillary conservation, these results indicate that some patients may be suitable for complete radiological staging of the axilla and thus safely avoid axillary surgery. Citation Format: Cox KL, Sharma N, Taylor-Phillips S, Weeks J, Mills P, Lim A, Haigh I, Sever A, Wallis M, DeSilva T, Hashem M. Enhanced pre-operative axillary staging using intradermal microbubbles and contrast-enhanced ultrasound (CEUS) to identify and biopsy sentinel lymph nodes (SLN) in breast cancer is a reproducible technique and may characterise a group of patients who can completely avoid axillary surgery [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 PD2-04.