RWE in oncology: use of databases to identify molecular subtypes of metastatic breast cancer in Italy

Introduction: The use of Real-World Evidence (RWE) is gaining increasing relevance in oncology, offering a complementary perspective to randomised clinical trials (RCTs). In Italy, administrative databases represent a promising source to explore treatment patterns and distribution of molecular subtypes in metastatic breast cancer(mBC). This study was aimed at evaluating the feasibility and accuracy of using administrative data to identify andcharacterise molecular subtypes of mBC in a setting of real clinical practice in Italy.Methods: Retrospective observational study conducted on a sample of about 4 million assisted patients. Datafrom different administrative flows were used to identify patients with mBC and to assign them to one of thethree main molecular subtypes (HR+/HER2-, HER2+, TNBC) through the use of proxies based on prescriptions ofdrugs and diagnostic codes.Results: Between January 2019 and June 2023, the observed distribution of subtypes was HR+/HER2- (74%),HER2+ (15%), and TNBC (11%), in line with the ranges reported in the literature. The model demonstrated a highconcordance with pre-existing epidemiological data.Conclusions: Administrative data are confirmed as a valid resource to describe the molecular landscape of mBCin Italy. The RWE emerges as a crucial tool to support clinical and regulatory decisions, promoting the approachof personalised medicine and the optimisation of healthcare resources.