Abstract P3-18-09: Refusal of breast surgery in breast cancer patients with clinical complete response (cCR) after neoadjuvant systemic therapy and vacuum-assisted biopsy (VAB) and sentinel lymph node biopsy (SLNB) confirmed pathological complete response (pCR). A first report of the prospective non-randomized trial results. NCT04293796

Abstract Introduction The aim of the study was to prove efficacy and safety of refusal of traditional breast surgery in BC patients who develop cCR after neoadjuvant chemotherapy. Refusal of surgery was offered to exceptional responders after vacuum-assisted tumor bed biopsy and sentinel lymph node biopsy confirmed absence of residual disease (pCR). Materials and methods A single-center prospective study was run in the NMRC n.a. N.N. Petrov. Starting from August of 2020 20 patients with early сT1-2N0-1M0 (stage Ia-IIb) triple-negative and HER2-positive (both ER+ and ER-) unifocal tumours without in situ component in core-biopsy specimen enrolled in the study. Primary lesions were marked with a single clip in the centre. In cases with nodal involvement (cN1) the affected lymph nodes were also clipped. Patients with triple-negative breast cancer received 4 cycles of AC q21d followed by 12 cycles of weekly paclitaxel and carboplatinum AUC 2.0. HER2-positive patients received 4 cycles of AC followed by 4 cycles of docetaxel combined with trastuzumab and pertuzumab q21d. Breast US, mammography and SPECT were used at baseline and at response evaluation. Vacuum-assisted biopsy was performed with 7G needle and US-guidance in the OR simultaneously with the SLNB under general anesthesia. VAB protocol included retrieval of the tumor clip as first stage. Subsequently surrounding tissues were sampled, and markers were placed to guide radiotherapy. In case residual tumor was found patients received standard breast-conserving surgery. In case the sentinel lymph nodes were found to be positive, standard level II axillary clearance was performed. HER2-positive patients with pCR confirmed by VAB and SLNB received adjuvant trastuzumab up to one year. HER2-positive patients with residual breast or nodal involvement received trastuzumab-emtanzine up to one year. In case ER-positive, all patients received appropriate endocrine-therapy. In case of residual in-breast or nodal involvement patients with triple-negative breast cancer received 6 cycles of capecitabine. Results cCR was achieved in 8 of 10 patients in the HER2-positive group. VAB and SLNB were performed in 7 cases and confirmed pCR in 5 patients. 2 had residual in-breast disease with <10% cellularity. One patient with cCR requested standard surgical approach that confirmed pCR. 2 patients failed to obtain cCR. Both received standard surgery. In one of the cases no residual disease was found, in another one - a residual in-breast tumor was found at section. All HER2-positive patients were found to be sn ypN0. In the triple-negative group cCR was achieved in 6 of 10 patients. 4 patients went on to receive VAB and SLNB. After VAB and SLNB pCR was confirmed in three of them. 1 patient had residual tumor with less than 5% cellularity. Two patients with cCR after NAT opted for standard surgery. In both cases pCR was confirmed. 4 patients with clinically detectable residual in-breast tumor received standard surgery. All turned out to have pCR. All the patients in the TNBC group were also found to be sn ypN0.ConclusionVisualization modalities fail to provide reliable information on the true rate of pCR. Contemporary systemic therapy regimens provide the rate of pCR up to 60-70%. In all cases of NAT tumor bed marking at baseline is an essential procedure to guide future interventions and confirm their success. Discrepancies between radiologic assessment and true rates of pCR are a substrate for further search for the techniques that would challenge the role of surgery in exceptional responders developing cCR. The trial continues to enrol patients. Citation Format: Petr Krivorotko, Sergey Yerechshenko, Alexander Emelyanov, Ekaterina Busko, Alexander Bessonov, Viktoriya Gukova, Alexander Komyahov, Elena Zhiltsova, Kirill Nikolaev, Tengiz Tabagua, Larisa Gigolaeva, Roman Pesotsky, Sergey Novikov, Zhanna Bryantseva, Anna Artemyeva, Viktoriya Smirnova, Vladimir Kushnarev, Alexey Belyaev, Tatiana Semiglazova, Vladimir Semiglazov. Refusal of breast surgery in breast cancer patients with clinical complete response (cCR) after neoadjuvant systemic therapy and vacuum-assisted biopsy (VAB) and sentinel lymph node biopsy (SLNB) confirmed pathological complete response (pCR). A first report of the prospective non-randomized trial results. NCT04293796 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-09.