Prognostic implications of risk definitions from the monarchE and NATALEE trials

Background: The monarchE and NATALEE trials employed different high-risk inclusion criteria. Main objective is to assess prognostic differences based on their inclusion criteria. Methods: Patients with hormone receptor-positive/HER2-negative early breast cancer enrolled in the phase III MIG1, GIM2, and GIM3 trials were categorized as high-risk cohort (HRC) and low-risk cohort (LRC) according to the inclusion criteria of monarchE and NATALEE trials. Subsequently, they were further classified in three different cohortsconcordant LRC (low-risk for both trials), discordant risk cohort (high-risk for only one trial), and concordant HRC (high-risk for both trials). Main outcomes were disease-free survival (DFS) and overall survival (OS). Results: Among 4,795 patients included, 1,343 (28.0%) and 2,689 (56.1%) were classified as HRC according to the monarchE and NATALEE, respectively.