ERBB2 and breast cancer: In a phase III clinical trial, compared to treatment with fulvestrant and placebo, treatment with alpelisib and fulvestrant increased the response rate and prolonged progression-free survival (PFS) in patients with PIK3CA-mutated HR+/HER2− advanced breast cancer (hazard ratio for progression or death, 0.65; 95% confidence interval, 0.50-0.85; p < 0.001) [53].