Abstract
BACKGROUND: Despite adjuvant endocrine therapy (ET), recurrence is still a concern for patients with HR+/HER2- early breast cancer (EBC). We assessed recurrence risk in real-world patients with stage II/III HR+/HER2- EBC treated with adjuvant ET. METHODS: A retrospective analysis was conducted using the ConcertAI Patient360 database (January 1995 to April 2021) of patients with stage II/III HR+/HER2- EBC ≥18 years who underwent surgery and received adjuvant ET. Risk of recurrence was assessed using invasive disease-free survival (iDFS) with adapted STEEP criteria. An ET subanalysis evaluated iDFS, distant disease-free survival, and overall survival in patients receiving adjuvant non-steroidal aromatase inhibitors (NSAI) vs tamoxifen. RESULTS: In the full analysis cohort (N = 3133), the risk of an iDFS event was 26.1 % at 5 years, rising to 45.0 % at 10 years. Among patients with stage II disease, the risk of an iDFS event at 5 and 10 years was 22.7 % and 40.5 %, respectively; stage III 5- and 10-year risk was 40.4 % and 62.9 %. Patients with node-negative disease had 5- and 10-year risks of 22.1 % and 36.9 %, respectively; node-positive 5- and 10-year risk was 28.9 % and 49.4 %. ET subanalysis showed improved iDFS with NSAI ± ovarian function suppression vs tamoxifen ± ovarian function suppression (HR, 0.83; 95 % CI, 0.69-0.98; p = 0.031); this trend was observed regardless of menopausal status. CONCLUSIONS: This real-world study highlights the considerable risk of recurrence with adjuvant ET in patients with stage II or III HR+/HER2- EBC (including node-negative disease) and confirms the need for improved treatment options.