Percutaneous Biopsy After Neoadjuvant Chemotherapy.

Neoadjuvant chemotherapy is widely used in the treatment of locally advanced breast cancer or in early stages of triple-negative or HER2 overexpressing tumors. Pathological complete response (pCR) to neoadjuvant chemotherapy is associated with better clinical outcomes. However, confirmation of pCR still depends on surgery, which may represent overtreatment for some patients. In this context, image-guided vacuum-assisted percutaneous biopsy (VAB) has been investigated as an alternative to assess tumor response and potentially avoid breast surgery in the future. However, there are no studies evaluating this strategy in brazilian patients, the majority of whom present with locally advanced tumors at diagnosis. To evaluate the accuracy of VAB in predicting mammary anatomopathological response in breast cancer patients undergoing neoadjuvant chemotherapy. This is a cross-sectional study conducted at the Cancer Institute of the State of São Paulo (ICESP). It will include patients with invasive mammary carcinoma cT1-T3, N0-N1, M0, of any immunohistochemical profile, with complete clinical and imaging response or residual lesion ≤ 2 cm after neoadjuvant chemotherapy. VAB will be guided by ultrasound or stereotaxy, with at least six fragments obtained and shaving of the remaining area. The concordance between VAB findings and surgical specimen will be analyzed by sensitivity, specificity, and accuracy.