Abstract ES11-3: Local treatments in patients who achieve pathologic complete response

Abstract

Abstract Local regional treatment of breast cancer has been historically based on anatomic extent of disease in the breast and ipsilateral axilla at presentation. An adjustment in this paradigm is evolving as more breast cancer patients receive neoadjuvant systemic therapy with increasingly more effective agents leading to higher rates of pathologic complete response. In the neoadjuvant setting, breast cancer subtype and pathologic complete response (pCR) may prove to have similar influence on local regional treatment as anatomic stage at presentation. In the ALLIANCE-ACOSOG 1071 clinical trial, rates of pCR (breast and axilla) were highest in the triple-negative (38.2%) and HER2-positive (45.4%) cases and similarly had the highest breast conservation rates of 46.3% and 43.8%, respectively. In addition, breast cancer patients that present with clinical N1 axillary involvement and have complete pathologic response can potentially avoid axillary node dissection with careful use of sentinel node biopsy based on the Sentina and SN FNAC trials. It may be that surgical resection will prove unnecessary for breast conservation in select cases with complete clinical and imaging response when breast radiation is intended and clinical trials are underway. Radiation therapy indications have likewise been established from extent of disease when surgery is the first line of therapy. Retrospective analyses of local regional recurrence incidence in neoadjuvant chemotherapy clinical trials demonstrates it is lowest in those with pathologic compete response in the breast and axillary nodes; as shown in a combined analysis of the NSABP B18 and 27 trials and again seen from analysis of the EORTC 10994/ BIG 1-00 trial. The ongoing NRG NSABP B51 RTOG 1304 clinical trial will determine if regional nodal irradiation is beneficial if positive axillary nodes at presentation convert to negative by neoadjuvant chemotherapy. Complete pathologic response may allow complete omission of post mastectomy radiation in some settings as well reduced extent of breast radiation following breast-conserving surgery. Citation Format: J White. Local treatments in patients who achieve pathologic complete response [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr ES11-3.