PIK3CA and breast cancer: Three out of 4 patients in PR had documented PTEN mutations (3 out of 5 patients with PTEN mutations enrolled on study achieved PR; Supplementary Table S2); 2 of these patients (2/4) had concomitant alterations in the PI3K pathway, that is, these patients had documented lesions in PTEN and STK11 (patient with breast cancer), PTEN and TSC2 (patient with leiomyosarcoma), respectively.