Abstract PO2-16-07: Real-world eligibility for adjuvant CDK4/6 inhibitors among patients without genomic risk for chemotherapy: a GBECAM multicenter retrospective study

Abstract Background: Oncotype DX (ODX) is a genomic signature (GS) for the prediction of risk of recurrence and benefit of chemotherapy (CT) in both node negative (N0) and positive (N1), hormone receptor positive (HR+), HER2 negative (HER2-) early breast cancer (eBC). ODX was not an inclusion criterion in the MonarchE but was one in the Natalee study, in which trials most patients received neo-adjuvant chemotherapy. We aim to evaluate the proportion of patients potentially eligible for adjuvant CDK4/6 inhibitors (CDK4/6i) without CT indication by genomic risk using real-world data from a large dataset of patients from various Brazilian institutions. Methods: Clinicopathologic and ODX information were reviewed for patients with T1-T3, N0-N1, HR+/HER2- eBC who had an ODX performed between 2005 and 2020. Projections of CT indication by genomic criteria were based on TAILORx and RxPONDER data. Projections of adjuvant CDK4/6i indication were based on the MonarchE and Natalee criteria. Results: Of 636 patients, 27.5%/51.8%/20.8% were T1mic-a-b/T1c/T2-3, respectively. 19.5% were grade 1 (G1), 66.9% G2 tumors and 12.9% G3. 74 (11.6%) were N1. The ODX indicated low (< 11), intermediate (11-25) and high ( >25) risk in 117 (18.4%), 408 (64.1%) and 111 (17.5%) patients, respectively. 408 patients (64.2%) had low clinical risk and 228 patients (35.8%) had high clinical risk disease. In the overall cohort, 439 (69%) did not have genomic indication for CT, 25 (3.9%) and 133 (21%) were eligible for adjuvant abemaciclib and ribociclib, respectively. Among patients eligible for adjuvant CDK4/6i, greater than 50% did not meet genomic criteria for recommendation of CT (Table 1). Conclusions: In times of rapid incorporation of both GES (as valuable treatment de-escalation tools) and adjuvant CDK4/6i, our results suggest that a meaningful proportion of patients could be eligible for adjuvant abemaciclib and/or ribociclib independently of CT indication. However, little is currently known about the role of these agents in patients not treated with chemotherapy because they were largely unrepresented in these studies. Proportion of patients eligible for adjuvant CDK4/6i in the overall and non-CT eligible population. CT: chemotherapy Citation Format: Leandro Oliveira, Thais Megid, Daniela Rosa, Daniele Assad-Suzuki, Daniel Argolo, Solange Sanches, Laura Testa, José Bines, Rafael Kaliks, Débora Gagliato, Romualdo Barroso-Sousa, Tatiana Correa, Andrea Shimada, Daniel Batista, Daniel Musse, Marcelle Cesca, Débora Gaudêncio, Larissa Moura, Julio Araujo, Renata Colombo Bonadio, Artur Katz, Max Mano. Real-world eligibility for adjuvant CDK4/6 inhibitors among patients without genomic risk for chemotherapy: a GBECAM multicenter retrospective study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-07.