185P Prospective study to evaluate pathological complete response after neoadjuvant therapy in breast cancer: Are we ready to avoid surgery?

Abstract

The complete pathological response (pCR) to Neoadjuvant treatment (NAT) is a favorable prognostic value,but response rates vary depending on subtype of breast cancer. A de-escalation of locoregional therapy after NAT will permit less radical operative procedures and a personalized therapy. For an accurate identification of such patients, there is a need for better predictors of pCR. We hypothesized that an ultrasound (US)-guided biopsy in addition to the imaging could improve the assessment of pCR. In this pilot study, we aimed to evaluate the concordance of pathological results between the samples obtained by US-guided VABB and by surgery in the assessment of pCR in patients with imaging complete response (iCR). This mono-institutional, prospective pilot study was conducted at the European Institute of Oncology (IEO) Eligible participants were TN and/or HER2+ invasive ductal breast cancer, who were treated with NAT. Patients with multifocal, multicentric, and contralateral breast cancers, microcalcifications at mammography, diagnosis of associated ductal carcinoma in situ (DCIS), and/or presence of chronic or psychiatric disorders were excluded from this study. For each participant, imaging assessment including MRI and PET/CT was performed before and after the NAT, and iCR was defined as the absence of imaging abnormality. A marker clip was placed in tumor bed in all participants before NAT. After NAT, participants with iCR underwent US-guided VABB to the marked tumor bed. Pathologic complete response was defined as no residual disease in hystological exam of the breast. 22 patients achieved iCR and were selected for the primary analyses. Only in 1 patient the pre-surgical VABB examination reported no pCR while at surgery the sample showed a minimally residual disease. Imaging alone after NAT lacks in predicting pCR but adding a VABB of the bed tumor increase the accuracy, and therefore it could be utilized for appropriate selection of patients for de-escalation of surgery. The omission of breast surgery for responders to NAT might someday become the next fundamental change of clinical practice. Our results in patients with TN and HER2+ breast cancer support this approach.