A phase II single-arm study of palbociclib in patients with HER2-positive breast cancer with brain metastases and analysis of ctDNA in patients with active brain metastases

Palbociclib did not demonstrate activity among patients with metastatic HER2+ breast cancer with brain metastases, according to data from a single-arm phase 2 trial. The best response was stable disease (6 patients) and progressive disease (6 patients). Analysis of ctDNA from blood showed that patients with progressive brain metastases but stable, responding, or absent systemic disease have low VAF and number of alterations.