Vacuum Assisted Biopsy and Surgery Correlation in HER2 and TN Breast Cancer Subtypes MRI Responders After Neoadjuvant Therapy: BISUCO TRIAL

BACKGROUND AND CURRENT STATUS: Advancements in neoadjuvant systemic treatments (NST) for HER2 positive and triple-negative (TN) breast cancer (BC) subtypes have led to high rates of pathologic complete response (pCR), raising questions about the necessity of subsequent surgery, especially for those undergoing adjuvant radiotherapy. While Magnetic Resonance Imaging (MRI) remains the most effective imaging technique for assessing neoadjuvant treatment response, surgery is still required to confirm pCR in cases of almost complete or complete MRI response (iCR). To safely avoid surgery in these BC "exceptional responders," a technique with high negative predictive value is imperative. OBJECTIVE: This study aims to establish the diagnostic efficacy of image-guided vacuum-assisted biopsy (VAB) in assessing pathological complete response (pCR) after NST in HER2 positive or TN breast cancer subtypes, particularly those showing post NST-MRI complete or almost complete response. METHODS: A prospective study was conducted at "Hospital Universitario 12 de Octubre de Madrid" from June 25, 2018, to October 25, 2029. Twenty-five patients with HER2-positive or TN operable invasive ductal carcinoma (IDC) BC subtype, at stages cT1-3/N0-2 undergoing primary NST and showing complete or almost complete response on post NST-MRI, were enrolled. Ultrasound or stereotactic-guided vacuum-assisted biopsy (VAB) of the previous clip and tumor bed area was performed before surgery. VAB pathological results were compared with surgical pathological results to evaluate the diagnostic efficacy of predicting pCR with VAB after NST. Pathological representativeness of the VAB sample was ensured. pCR was defined as the absence of invasive ductal carcinoma and in situ ductal carcinoma.