Abstract P4-09-04: Vacuum-assisted biopsy (VAB) versus standard breast surgery among patients with pCR after neoadjuvant therapy

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Abstract Introduction. Nowadays, in patients with breast cancer (BC) and complete pathological response (pCR) after neoadjuvant systemic therapy (NST) role of surgery is uncertain. Vacuum-assisted biopsy (VAB) of the tumor bed in breast cancer has shown promising results as a minimally invasive method for diagnosing pCR. In a NCT04293796 clinical trial we are investigating refusion of standard breast cancer surgery among patients with pCR, which was confirmed using VAB. This paper presents a retrospective analysis of treatment of patients with triple-negative (TNBC) and HER2-positive breast cancer who achieved pCR after NST, depending on different types of invasive breast surgery, including data from patients who underwent VAB alone without subsequent breast surgery. Materials and Methods. We retrospectively analyzed 3247 patients who underwent surgery in the department of breast tumors at the National Medical Research Center of Oncology named after. N.N. Petrov from January 01, 2021 until July 01, 2023. Patients were included if they had unifocal invasive HER2+ and TNBC (cT1–2N0–1M0), who had histologically confirmed pathological complete response (ypT0N0) after NST. Patients with TNBC received 4 cycles of AC q21d followed by 12 cycles of weekly paclitaxel and carboplatin AUC 2.0. HER2+ patients received dual anti-HER2 blockade with chemotherapy (TCHP or AC-DHP regimen). Patients were not included in the analysis if an intraductal component was identified by core-biopsy, as well as if they carried germline mutations in the BRCA1/2 genes. All patients were divided into three groups: breast-conserving surgery (BCS) group, the mastectomy (ME) group, and the VAB group. Primary endpoint was 2-year ipsilateral breast tumor recurrence-free survival (IBTR-FS). Secondary endpoint was 2-year disease-free survival (DFS). Results. Of the 3247 patients analyzed, 81 patients who met the inclusion criteria were included in the final analysis. There were 39 patients in the BCS group, 19 patients in the ME group, and 23 patients in the VAB group. Median follow-up was 24 months. Median survival was not reached for any endpoint. 2-year IBTR-FS was 100% in the BCS group vs. 100% in the ME group vs. 91.3% in the VAB group [p=.159]. 2-year disease-free survival (DFS) was 97.4% in the BCS group vs 94.7% in the ME group vs 87.0% in the VAB group [p=.396]. The hazard ratio (HR) for recurrence did not differ depending on the surgical procedure performed. When measuring HR adjusted for lymph node status (cN) and disease stage, there was a statistically significantly higher risk in the VAB group [HR adjusted for cN: 12.236, (95% CI, 1.163 - 128.773), p = 0.037; HR adjusted for stage: 17.071, (95% CI, 1.255 – 232.173), p=0.033]. Conclusion. We need further observational studies and large randomized prospective trials to determine the safety of VAB as a method for de-escalation of breast cancer surgery. Citation Format: Nikolay Amirov, Petr Krivorotko, Alexander Emelyanov, Viktoriia Mortada, Roman Pesotsky, Tengiz Tabagua, Anna Artemyeva, Sergey Yereschenko, Elena Zhiltsova, Yana Bondarchuk, Diana Enaldieva, Daria Ulrikh, Sergey Novikov, Zhanna Bryantseva, Irina Akulova, Ekaterina Busko, Tatiana Semiglazova, Vladimir Semiglazov. Vacuum-assisted biopsy (VAB) versus standard breast surgery among patients with pCR after neoadjuvant therapy [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P4-09-04.

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