PIK3CA and breast cancer: In human epidermal growth factor receptor 2-positive (HER2+) breast cancer patients undergoing HER2-targeted treatment, patients with PIK3CA mutations showed lower progression-free survival (PFS) than those with wild-type PIK3CA (hazard ratio (HR) 4.602, 95% CI 2.057–10.514, p < 0.001) [6].