Abstract PO1-02-09: Efficacy of breast conserving treatment of minimal residual tumors after neoadjuvant therapy for breast cancer
Authors: Pesotsky Roman , Semiglazov Vladimir , Krivorotko Petr , Tabagua Tengiz , Zernov Konstantin , Emelyanov Alexander , Mortada Viktoria , Amirov Nikolay , Ulrikh Daria , Levchenko Valerii , Bondarchuk Yana , Enaldieva Diana , Bekkeldieva Nestan , Zirov Konsantin , Yerechshenko Sergey , Evseev Vladislav , Rychagov Kirill , Novikov Sergey , Kazantseva Maria , Gigolaeva Larisa , Zhiltsova Elena , Nesterov Denis , Ivanova Olga , Semiglazova Tatiana 
Published: May 2024

Abstract
Background. Determining the most effective drug therapy regimens is one of the top priorities in the individualization of the treatment of patients with breast cancer (BC). Achievement of pathological complete response (pCR) is important prognostic factor, and used as the surrogate primary end point in many clinical trials. According to the literature, the achievement of pCR after neoadjuvant systemic treatment (NST) in breast cancer varies from 30 to 70%. Patients who do not achieve pCR require post-neoadjuvant treatment, even when reaching minimal size of residual tumors. Initially, primary minimal tumors are characterized by high survival rates, which are proved by international and domestic studies. It is required to clarify the survival rates in the presence of a minimal residual tumor (ypT &lt; 10mm) after neoadjuvant systemic therapy and to compare with primary minimal forms of breast cancer (pT1a-b N0M0), characterized by the most favorable prognosis. Objective. Improvement of the effectiveness of treatment of residual minimal forms (ypT1a-b) of BC after NST. Determination of the correlation between the schemes of NST and the rates of tumor response based on the results of postoperative pathological reports including RCB scale. Methods. The study included 602 patients aged 18–65 years with early and locally advanced I–IIIC stage T1-3N1-3M0 breast cancer,who underwent complex or combined treatment. This study included patients treated at the N.N. Petrov National Medical Research Center of Oncology from 2015 to 2021 Conclusion. After reaching a complete pathomorphological response of the tumor to NST (RCB 0), the 5-year disease-free (DFS) and overall (OS) survival rates (DFS – 78.5%; OS 90.4%) were inferior to the survival rates of patients with primary minimal breast cancer (pT1ab N0M0) [DFS – 86.4%; OS – 98.6%]. Neoadjuvant chemotherapy regimens that allow achieving a pathological complete response in triple-negative and HER2- positive breast cancer have been defined. An assessment of adverse factors that affect the effectiveness of breast conserving treatment and correlate with a deterioration in overall survival was performed. Results. Our data analysis revealed that the survival rates (DFS and OS) of patients with minimal residual tumor after neojuvant systemic therapy were not comparable with those in the group of patients with primary minimal breast cancer. Data analysis revealed the most effective combinations of drugs expressed in the rates of pathomorphological response according to the RCB scale. An assessment of adverse factors that affect the effectiveness of organ-preserving treatment and correlate with a deterioration in overall survival was performed.

Citation Format: Roman Pesotsky, Vladimir Semiglazov, Petr Krivorotko, Tengiz Tabagua, Konstantin Zernov, Alexander Emelyanov, Viktoria Mortada, Nikolay Amirov, Daria Ulrikh, Valerii Levchenko, Yana Bondarchuk, Diana Enaldieva, Nestan Bekkeldieva, Konsantin Zirov, Sergey Yerechshenko, Vladislav Evseev, Kirill Rychagov, Sergey Novikov, Maria Kazantseva, Larisa Gigolaeva, Elena Zhiltsova, Denis Nesterov, Olga Ivanova, Tatiana Semiglazova. Efficacy of breast conserving treatment of minimal residual tumors after neoadjuvant therapy for breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-02-09.