Safety of Breast Conserving Treatment in Locally Advanced Breast Cancer Receiving Neoadjuvant Treatment

The standard breast surgical procedure of locally advanced breast cancer in Norway is mastectomy. There is increasing interest in performing breast conserving treatment (BCT) in locally advanced cases after chemotherapy or hormonal treatment - if there is a partial or complete clinical remission. To increase the evidence for the safety (no residual tumor) of such a procedure directly compared to mastectomy without compromising the safety of the treatment, a breast preserving procedure followed by an immediate mastectomy can be performed within a study. It would then be possible to study the margins after the breast preserving procedure as well as the tumor status in the rest of the breast.

Patients included in the study will receive neoadjuvant treatment followed by evaluation of the tumor reduction by magnetic resonance imaging (MRI) and selection of BCT candidates. Candidates will be prepared for BCT, and during the surgical procedure, BCT will be performed (as one surgical specimen) followed by immediate removal of the rest of the breast tissue (mastectomy). The BCT specimen and mastectomy specimen will be analysed for residual tumor cells. The tumor removal completeness of the BCT procedure can be evaluated, with comparison to the clinical and primary tumor characteristics, including analysis of the tumor biopsies and imaging before and during the neoadjuvant treatment, for selection of candidates for BCT in the future.