Given that anti-proliferative responses using KI67 were developed for ER-positive BC treated with endocrine agents, we looked at the relationship between the PIK3CA-GS, PIK3CA genotype and changes in phosphorylated S6 (pS6 S240) detected using IHC in the pre-surgical study cohort of dataset B (everolimus alone). The gene discussed is PIK3CA; the disease is breast cancer.