De-escalation of breast cancer surgery using vacuum-assisted biopsy (VAB): Interim results.

Abstract

e12590 Background: Currently, there is a point of view according to which, in patients diagnosed with breast cancer (BC), surgical intervention when achieving a complete pathological response (pCR) after neoadjuvant systemic therapy (NST) is diagnostic, not therapeutic, and does not affect long-term treatment outcomes. Vacuum-assisted biopsy (VAB) of the tumor bed in breast cancer has shown promising results as a minimally invasive method for diagnosing pCR. This work presents a prospective analysis of treatment of patients with triple-negative and HER2-positive breast cancer who achieved pCR after NST and who underwent VAB alone without subsequent breast surgery. Methods: Women aged 18 years old and older with unicentric (cT1-2N0-1M0) triple-negative or HER2-positive breast cancer were included. Primary lesions were marked with a single clip before NST. In cases with nodal involvement (cN1) the affected lymph nodes were also clipped. 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). Breast US, mammography and mammolymphoscintigraphy were used at baseline and at response evaluation. Patients with complete clinical response after NST underwent VAB with 7G needle and US-guidance simultaneously with the sentinel lymph node biopsy and/or targeted axillary dissection. In case if no invasive or in situ residual tumor cells were detected (ypT0N0), no further breast surgery was performed and patients underwent subsequent radiation therapy. Primary endpoint was 2-year ipsilateral breast tumour recurrence-free survival [IBTR-FS]. Secondary endpoints included 2-year disease-free survival (DFS) and complication rates. The study is registered on сlinicaltrials.gov, NCT04293796. Results: 35 patients with a mean age of 48.3 (31–67) years were included in the trial. Examination of VAB samples showed that 11 (31.4%) patients had a residual tumor, and in 24 (68.6%) patients no tumor cells were detected (ypT0N0). This 24 patients were included in the analysis. Median follow-up was 26 months. Median survival was not reached for any endpoint. 2-year IBTR-FS was 91.7% in the VAB group. 2-year DFS was 83.3% in the VAB group. We registered 4 events: in 2 patients biopsy-proven de novo breast cancer occurred in contralateral breast, in 1 patient recurrence occurred in the postoperative zone and in 1 patient recurrence occurred in another quadrant of the ipsilateral breast. Conclusions: Additional observation and large randomized prospective studies are needed to determine the safety of VAB use. Clinical trial information: NCT04293796 .