Real-world effectiveness of aromatase inhibitors and fulvestrant in HR+/HER2- advanced breast cancer: a snapshot of the last two years before conventional use of CDK 4/6 inhibitors in a Portuguese institution.

Estimated effectiveness (OS) of letrozole and fulvestrant was, respectively, 3.2-3.5 months lower than reported. The clinical meaning seems uncertain and may be explained a higher proportion of worse prognostic characteristics in patients treated in the real-world.