Background: Quality indicators (QIs) for the management of breast cancer (BC) have been published in Europe and internationally. In Belgium, a task force was established to select measurable process indicators of systemic treatment for BC, focusing on appropriateness of delivered care. The objective of this study was to evaluate the results of the selected QIs, both nationally and among individual centres. Patients and Methods: Female Belgian residents with unilateral primary invasive BC diagnosed between 2010 and 2014 were selected from the Belgian Cancer Registry database. The national number enabled linkage with the national reimbursement database, which contains information on all reimbursed medical procedures. A total of 12 process indicators were measured on the population and hospital level. Intercentre variability was assessed by median results and interquartile ranges. Results: A total of 48 872 patients were included in the study. QIs concerning specific BC subtypes only applied to patients diagnosed in 2014 (n = 9855). Clinical stage (cStage) I patients (n = 17 116) were staged with positron emission tomography/computed tomography. Among patients who were pT1aN0 human epidermal growth factor receptor 2 (HER2) positive (n = 47), 25.5% (n = 12) received adjuvant trastuzumab. Among patients with de novo metastatic luminal A/B-like HER2-negative BC (n = 295), 17.3% (n = 51) received upfront chemotherapy. (Neo)adjuvant chemotherapy was administered in 52.4% (n = 12 592) of operated women with cStage I-III, in 37.0% (n = 1270) of operated women with cStage I-III luminal A/B-like HER2-negative BC, and in 19.1% of operated women with cStage I luminal A/B-like HER2-negative BC. In the population of operated patients with cStage I-III, of those younger than 70 years that started adjuvant endocrine therapy (n = 3591), 81.7% (n = 2932) continued treatment for ≥4.5 years. Among patients in cStage I-III older than 70 years (n = 8544), 19.0% (n = 1622) received (neo)adjuvant chemotherapy, whereas among patients with ...