Several treatment guidelines exist for hormone receptor-positive/HER2-negative advanced breast cancer (HR+/HER2- aBC), but various factors influence their local implementation. We performed a 3-round Delphi methodbased study in search of a consensus regarding HR+/HER2- aBC management in Belgian practice. Panel questionnaires included questions related to treatment patterns, drug-drug interactions (DDIs) and side-effect management (SEM). A consensus threshold of 75% was applied. The results were evaluated for concordance with the ABC5 guidelines. Treatment patterns in HR+/HER2- aBC reached moderate to high consensus among Belgian oncologists and showed high concordance with ABC5 guidelines. A CDK4/6 inhibitor is the preferred first-line treatment, combined with an aromatase inhibitor or with fulvestrant in the endocrine-sensitive and -resistant setting, respectively. Alpelisib-fulvestrant is the preferred second-line treatment in presence of a PIK3CA-activating mutation. Some practices regarding DDI and SEM needed further discussion before reaching consensus highlighting the need for additional training and incorporation of these topics in guidelines.

(BELG J MED ONCOL 2022;16(4):176–86)