Trastuzumab treatment of patients with early, HER2-positive breast cancer in 17 certified German breast cancer centers

Purpose Since 2008, guidelines recommend that patients with HER2-positive early breast cancer (BC) should receive adjuvant chemotherapy in combination with trastuzumab in Germany. However, recent studies highlight that a substantial share of patients do not receive trastuzumab. We investigate which patient characteristics are associated with a tumor board recommendation for trastuzumab in Breast Cancer Centers (BCC) certified by the German Cancer Society (DKG) and the German Society for Senology, and if the recommendation differs between BCCs. Materials and methods Multi-level modeling was performed using quality assurance data based on 3052 HER2-positive, operated patients with a first diagnosis of early BC treated between 2006 and 2019 in 17 BCCs in Germany to investigate whether trastuzumab recommendation varies with patient sex, age, and disease characteristics, as well as over time and across BCCs. Results Tumor board recommendations for trastuzumab differ substantially between BCCs (intraclass correlation coefficient [ICC] null model: 0.11). Our final model (ICC 0.17, Akaike Information Criterion [AIC], 1328.0, R 2 0.69) shows that physicians in BCCs more often recommend trastuzumab to patients who are younger than 60 years and those with a recommendation for any additional therapy (chemotherapy, radiation or endocrine therapy) (all p