Abstract P3-03-03: Sentinel node biopsy (SNB) vs Low axillary sampling (LAS) in predicting nodal status of post-chemotherapy axilla in women with breast cancer

Abstract

Abstract Introduction There is no safe method of avoiding complete axillary lymph node dissection in women with breast cancer after neo-adjuvant chemotherapy. sentinel node biopsy (SNB) has had prohibitively high false negative rate. We tested low axillary sampling (LAS) and SNB performed in same patient to predict axillary lymph node status in clinically node negative women undergoing breast conservation or modified radical mastectomy after neo-adjuvant chemotherapy. Methodology Post neo-adjuvant chemotherapy 751 women who had no palpable axillary lymph node underwent LAS (all lymph nodes below intercosto-brachial nerve). Of these 751 women, 730 also underwent SNB by dual technique after injection of blue dye as well as radio-isotope. SN was identified within and outside axillary sampling specimen. SN as well as LAS specimens were distinctly examined for nodal metastasis. The rest of the axillary dissection was completed in all patients. Post NACT 292/751(38.9%) had residual positive lymph nodes on pathology. The identification rate, false negative rate (FNR), and negative predictive value (NPV) of SNB and LAS were compared for predicting negative axillary lymph node status. Results The median clinical tumor size was 5cm (1-15cm) and 533(71%) patients were N1 or N2 at presentation. The SNB identification rate was 87.1% (636 of 730), with a median of 5 nodes and node positive in 238 of 636 (37.4%). LAS identification rate was 98% (736 of 751), with a median of 7 nodes and node positive in 292 of 736 (39.6%). In all but one case, the SN was found within the LAS specimen. The FNR of SNB (blue, hot and adjacent palpable nodes) was 19.7% (47 of 238, one sided 95% upper CI 24.0) compared to LAS with FNR of 9.9% (29 of 292, one-sided 95% upper CI 12.8) (p<0.001). Comparative NPV for SNB and LAS were 89.4% and 93.9% respectively. If SNB was confined to blue/hot node excluding adjacent palpable nodes, FNR was 31.6% (74 of 234, 95% upper CI 36.6). Conclusions LAS is superior to SNB in identification rate, FNR and NPV in predicting node negative axilla post-neoadjuvant chemotherapy. LAS can be safely used to predict negative axilla with less than 10% chance of leaving residual disease. Citation Format: Parmar V, Nair NS, Vanamali V, Hawaldar RW, Siddique S, Shet T, Desai SB, Rangarajan V, Patil A, Gupta S, Badwe RA. Sentinel node biopsy (SNB) vs Low axillary sampling (LAS) in predicting nodal status of post-chemotherapy axilla in women with breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-03.