MKI67 and breast carcinoma: The WSG-ADAPT (20) trial tested a de-escalation approach following identification of early responders: in largely stage 1 HER2-positive HR-negative breast cancers, after Ki67 assessment at 3 weeks of pertuzumab and trastuzumab, patients were randomized to continued dual agent therapy up to 12 weeks, or combined it with weekly paclitaxel.