After the treatment of PI3K inhibitors, HR+ breast cancer patients with PIK3CA mutations presented better ORR (PIK3CA-mutated group: OR = 1.98 [95% CI, 1.46 to 2.70]; PIK3CA wild-type group: OR = 1.09 [95% CI, 0.78 to 1.53]) and better PFS (PIK3CA-mutated group: HR = 0.65 [95% CI, 0.55 to 0.76]; PIK3CA wild-type group: HR = 0.87 [95% CI, 0.70 to 1.09]). This evidence concerns the gene PIK3CB and breast cancer.