ERBB2 and neoplasm: Of note, patients with SHR-positive HER2-negative tumours who were treated with aromatase inhibitors only (n = 208), had a significant 4.39 times higher occurrence of RFI events if they harboured a PIK3CA-mutation (n = 68) compared to those with PIK3CA-wildtype (n = 140; adjusted HR 4.39, 95% CI 1.385–13.920, p = 0.012; Fig. 2C, Table S3A) and a significantly impaired OS (adjusted HR 2.12, 95% CI 1.021–4.404, p = 0.044; Fig. 2D, Table S3B).