ERBB2 and breast cancer: Patients with HER2-positive breast cancer who received radiotherapy had, compared with patients who did not receive radiotherapy, a significantly improved OS (HR 0.1 [95% CI 0.03–0.50]; P = 0.003) and PFS (HR 0.2 [95% CI 0.06–0.60]; P = 0.004) (Fig. 4).