Abstract PD8-05: POSNOC - Positive sentinel node: Adjuvant therapy alone versus adjuvant therapy plus clearance or axillary radiotherapy

Abstract

Background: Role of additional axillary treatment (AxT) (axillary lymph node dissection (ALND) or axillary radiotherapy (ART)) in women with ≤2 macrometastases and undergoing systemic therapy remains unclear. Z11 included both micro and macrometastases (around 40% micrometastases) and showed that ALND may be omitted in women with ≤2 positive nodes undergoing breast conserving surgery (BCS) and receiving whole breast RT. Paradoxically, NCIC MA20, demonstrated improved DFS following the addition of regional RT. 51.8% (949/1832) had 1 or 2 positive nodes. 98.9% (1812/1832) had T1/T2 tumours. A post-Z11 survey shows that most US radiation oncologists treat the undissected axilla in women with macrometastases with ART rather than omitting AxT. Therefore, a confirmatory study is needed to clarify the role of additional AxT in women with ≤2 macrometastases undergoing BCS and other subgroups that were not included in Z11 e.g. mastectomy, microscopic extranodal invasion and sentinel node biopsy (SNB) before neoadjuvant chemotherapy. Methods: Primary objective is to assess whether for women with ≤2 macrometastases at SNB, systemic therapy alone is non-inferior to systemic therapy plus AxT in terms of axillary recurrence at 5 years. Secondary objectives are arm morbidity assessed by LBCQ and QuickDASH questionnaires; QoL assessed by FACT-B+4 questionnaire; anxiety assessed by STAI; loco-regional recurrence; distant metastasis; time to axillary recurrence; axillary recurrence-free survival; DFS; OS; contralateral breast cancer; non-breast malignancy; and economic evaluation. Eligibility criteria include: ≥18 y, uni or multifocal invasive cancer, T1/T2, 1 or 2 macrometastases, with or without extranodal invasion. Target sample size is 1900 with a projected drop-out and non-compliance with treatment allocation rate of 10%. Primary analysis will be per protocol. The following pre-specified subgroup analyses shall be performed: number of macrometastases (1, 2), age ( Citation Format: Goyal A, Mann B, Thompson AM. POSNOC - Positive sentinel node: Adjuvant therapy alone versus adjuvant therapy plus clearance or axillary radiotherapy [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 PD8-05.