ERBB2 and breast cancer: The effectiveness (in terms of pCR and 3-year DFS) of dual HER2 blockade with trastuzumab and pertuzumab with or without endocrine therapy in patients with HER2-positive, early-stage breast cancer who were [18F]FDG PET responders was examined in a multicenter, randomized, open-label, non-comparative phase-2 trial involving 45 hospitals in Spain, France, Belgium, Germany, the UK, Italy, and Portugal (PHERGain).