Pfizer's Ibrance has demonstrated efficacy in breast cancer patients with tumors that are positive for both the estrogen receptor and HER2, potentially expanding its use beyond the current 70% of patients with ER-positive, HER2-negative tumors. This new data could help mitigate Ibrance's market share losses to Novartis' Kisqali, which has shown improved survival rates in advanced breast cancer. While Ibrance has not proven to improve survival, this finding marks a significant step in its application for HER2-positive patients, who represent 10% of breast cancer cases.
