Abstract PD8-01: Microscopic extracapsular extension in sentinel lymph nodes does not mandate axillary dissection in Z0011-eligible patients

Abstract

Abstract Background In ACOSOG Z0011 and AMAROS, matted nodes with gross extracapsular extension (ECE)—a risk factor for locoregional recurrence—were an indication for axillary dissection (ALND), but the effect of microscopic ECE (mECE) in the sentinel nodes (SLNs) on recurrence was not examined. Methods Between 2010-2017, 815 patients with cT1-2N0 breast cancer and SLN metastasis were prospectively managed according to Z0011 criteria, with ALND for those with >2 positive SLNs. Management of mECE was not specified. Here we report outcomes of patients with 1-2 positive SLNs treated with SLN biopsy alone (n=685) and evaluate the impact of mECE on nodal recurrence. Outcomes of the 118 patients treated with ALND, of which 70% had >2 positive SLNs, are provided for comparison. Results Median patient age was 58 years and median tumor size was 1.7 cm. In the SLN group, 210 (31%) had mECE. Patients with mECE were older, had larger tumors, were more likely to be hormone receptor positive (HR+) and HER2-, have 2 positive SLNs, and to receive nodal radiation (Table). At a median follow-up of 41 months, no isolated axillary failures were observed. There were 11 nodal recurrences; 2 isolated, 4 synchronous with breast, and 5 with distant failure. The 5-year rate of any nodal recurrence was 1.6% and did not differ by mECE (2.3% vs 1.3%, p=0.84). No differences were observed in local (0% mECE vs. 1.9% no mECE, p=0.08) or distant (1.2% mECE vs. 4.6% no mECE, p=0.31) recurrence rates by mECE status. In comparison, in the 118 patients having ALND, 101 (86%) had mECE, and 1 combined nodal and distant recurrence was seen. Patient Characteristics Overall n=685No mECE n=475mECE n=210P valueAge, years (median, range)58 (30, 92)57 (30, 85)61 (34, 92)0.0002Pathologic tumor size, cm (median, range)1.7 (0.1, 5.2)1.6 (0.1, 5.2)1.8 (0.4, 5.2)0.008Histology 0.24Ductal598 (87%)421 (89%)177 (84%) Lobular59 (9%)34 (7%)25 (12%) Mixed24 (4%)17 (4%)7 (3%) Other4 (<1%)3 (<1%)1 (<1%) Subtype 0.006HR+/HER2-574 (84%)386 (81%)188 (90%) HR+/HER2+54 (8%)38 (8%)16 (8%) HR-/HER2+21 (3%)18 (4%)3 (1%) HR-/HER2-36 (5%)33 (7%)3 (1%) Total positive SLNs 0.031561 (82%)399 (84%)162 (77%) 2124 (18%)76 (16%)48 (23%) mECE size NA≤2mmNANA117 (56%) >2mmNANA93 (44%) Systemic therapy* 0.03Chemotherapy + endocrine424 (62%)284 (60%)140 (67%) Chemotherapy only67 (10%)55 (12%)12 (5%) Endocrine only172 (25%)118 (25%)54 (26%) Unknown§22 (3%)18 (4%)4 (2%) Radiation field* <0.0001Supine345 (50%)260 (55%)85 (40%) Prone111 (16%)93 (20%)18 (9%) Breast + nodes161 (24%)80 (17%)81 (39%) Unknown§68 (10%)42 (9%)26 (12%) *Analysis excludes unknowns; §Unknown includes no treatment, pending, and unknown; Abbreviations: mECE, microscopic ECE; HR, hormone receptor; SLNs, sentinel nodes Conclusions In Z0011-eligible patients, rates of nodal recurrence in patients with mECE are low after treatment with SLN biopsy alone, even in the absence of routine nodal radiation. The presence of mECE should not be considered a routine indication for ALND. Citation Format: Barrio AV, Downs-Canner S, Cody HS, Van Zee KJ, Gemignani ML, Pilewskie M, Plitas G, El-Tamer M, Kirstein L, Capko D, Patil S, Morrow M. Microscopic extracapsular extension in sentinel lymph nodes does not mandate axillary dissection in Z0011-eligible patients [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 PD8-01.