What adjuvant systemic therapy would you recommend for a premenopausal woman with a germline BRCA mutation who initially presented with locally advanced, HR+, HER2-negative (FISH) IDC, but was later found on surgical pathology to have HR+, HER2+ disease (IHC 3+) after neoadjuvant chemotherapy?

In a situation like this, I would consider 1 year of adjuvant trastuzumab and pertuzumab. The HERA study showed the benefit of adding trastuzumab after a full course of adjuvant chemotherapy for HER2+ breast cancer, which would provide some (although imperfect) evidence to support such an approach. ...

Agree with adjuvant HER2-targeted therapy. This is an unusual situation. Tarantino et al reported data on 1,080 patients treated at Dana Farber/Brigham Cancer Center from 2016-2022 who had residual disease after neoadjuvant chemotherapy. Of the 808 cancers that were HER2 0 or HER2-low on pre-op biop...