Trastuzumab without chemotherapy in the adjuvant treatment of breast cancer: subgroup results from a large observational study oleh Peter Dall, Thorsten Koch, Thomas Göhler, Johannes Selbach, Andreas Ammon, Jochen Eggert, Nidal Gazawi, Daniela Rezek, Arthur Wischnik, Carsten Hielscher, Nicolas Schleif, Ursula Cirrincione, Axel Hinke, Gabriele Feisel-Schwickardi