Long-term outcomes of high-risk HR-positive and HER2-negative early breast cancer patients from GEICAM adjuvant studies and El Álamo IV registry

PURPOSE: The monarchE trial showed that the addition of abemaciclib improves efficacy in patients with high-risk early breast cancer (EBC). We analyzed the long-term outcomes of a population similar to the monarchE trial to put into context the potential benefit of abemaciclib. METHODS: HR-positive/HER2-negative EBC patients eligible for the monarchE study were selected from 3 adjuvant clinical trials and a breast cancer registry. Patients with ≥ 4 positive axillary lymph nodes (N +) or 1–3 N + with tumor size ≥ 5 cm and/or histologic grade 3 and/or Ki67 ≥ 20%, who had undergone surgery with curative intent and had received anthracyclines ± taxanes and endocrine therapy in the neoadjuvant and /or adjuvant setting were included. We performed analysis of Invasive Disease-Free Survival (iDFS), Distant Disease-Free Survival (dDFS) and Overall Survival (OS) at 5 and 10 years, as well as yearly (up to 10) of Invasive Relapse Rate (IRR), Distant Relapse Rate (DRR) and Death Rate (DR). RESULTS: A total of 1,617 patients were analyzed from the GEICAM-9906 (312), GEICAM-2003–10 (210), and GEICAM-2006–10 (160) trials plus 935 from El Álamo IV. With a median follow-up of 10.1 years, the 5 and 10 years iDFS rates were 75.2% and 57.0%, respectively. The dDFS and OS rates at 5 years were 77.4% and 88.8% and the respective figures at 10 years were 59.7% and 70.9%. CONCLUSIONS: This data points out the need for new therapies for those patients. A longer follow-up of the monarchE study to see the real final benefit with abemaciclib is warranted. TRIAL REGISTRATION: ClinTrials.gov: GEICAM/9906: NCT00129922; GEICAM/ 2003-10: NCT00129935 and GEICAM/ 2006-10: NCT00543127. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10549-023-07002-1.