Abstract P3-03-12: Risk of recurrence with adjuvant endocrine therapy in real world patients with hormone receptor positive/human epidermal growth factor receptor-negative early breast cancer: a US database analysis

Abstract

Abstract Background The recommended 5-10 years of adjuvant endocrine therapy (ET) as standard of care has improved outcomes in patients with HR+/HER2− early breast cancer (EBC); however, risk of recurrence persists. The monarchE study demonstrated improvement in invasive disease-free survival (iDFS) with abemaciclib in node-positive, high-risk EBC, the majority of which were stage III (Johnston SRD, et al. J Clin Oncol. 2021;38:3987); however, monarchE’s relatively short follow-up time to date only allowed for observation of early recurrences—longer follow-up is needed to evaluate late recurrences. Risk of recurrence is a concern for patients with all stages of EBC (Pan H, et al. N Engl J Med. 2017;377:1836). We assessed the risk of recurrence in a real-world setting among patients with stage II-III HR+/HER2− EBC after initiation of adjuvant ET. Methods This was a retrospective analysis of ConcertAI’s deidentified electronic medical records data set among patients treated from January 1, 1995, to April 30, 2021. The cohort included stage II-III patients with HR+/HER2− EBC who underwent surgery and initiated adjuvant ET (if IIIB or IIIC, confirmation was required on residual tumor status). Patients were from academic and community oncology clinics across the US. Data were missing from the database for some variables; thus, percentages may not add up to 100%. iDFS was assessed to determine the risk of disease recurrence, death, or second primary tumor and was defined as the time interval between start of ET and first iDFS event. Kaplan-Meier methods were used to estimate cumulative probabilities of experiencing an iDFS event at 5 and 10 years from the start of ET. Results A total of 3133 patients (98.8% female) with stage II-III HR+/HER2− EBC were included in the analysis. The median follow-up time was 68.1 months. The median age was 59 years; 22.2% of female patients were pre/perimenopausal and 44.7% were postmenopausal; 80.9% of all patients had stage II disease, while 19.1% had stage III disease. In total, 42.1% and 3.7% of those with stage II and III disease had no nodal involvement, respectively. Overall, 51.2% of patients did not receive radiotherapy, and 59.5% of patients did not receive (neo)adjuvant chemotherapy. In the total sample, the 5- and 10-year risk of an iDFS event was 26.1% and 45.0%, respectively. In patients with stage II disease, the 5- and 10-year risks were 22.7% and 40.5%, respectively, and 40.4% and 62.9% among stage III. Conclusions These real-world data demonstrate that the risk of recurrence with adjuvant ET, particularly in those with stage II EBC, is higher than reported in many randomized controlled trials. Importantly, our data show that, in the real-world setting, the stage II population represents a significant proportion of patients (nearly 4 times more than stage III). These findings confirm and underscore the clear unmet need in this population and highlight the need for improved treatment options in this broader EBC population. The NATALEE study will investigate ribociclib + ET in a broad population of patients including stage II and stage III HR+/HER2− EBC with high-risk features, regardless of nodal status. Citation Format: Joyce O’Shaughnessy, Denise Yardley, Lowell Hart, Pedram Razavi, Stephanie L. Graff, Jenifer Wogen, Courtney McDermott, Pierre-Alexandre Dionne, Sina Haftchenary, Purnima Pathak, Sara Tolaney. Risk of recurrence with adjuvant endocrine therapy in real world patients with hormone receptor positive/human epidermal growth factor receptor-negative early breast cancer: a US database analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-03-12.