Abstract PO5-02-04: Irish National Analysis of the Clinical and Economic impact of 21-gene Oncotype DX® testing in Early-Stage, 1-3 lymph node positive, Hormone Receptor positive (HR+), HER2-Negative (HER2-), Breast Cancer (BC)

Abstract Background: The treatment landscape of HR+ BC is evolving, with a reduction in chemotherapy (CT) use because of Oncotype DX Recurrence Score® testing. Results from the RxPONDER trial suggest that adjuvant CT may benefit some premenopausal women with HR+, HER2- disease with 1-3 positive LN (N1), and a Recurrence Score® (RS) result of ≤25. Postmenopausal women with similar characteristics did not benefit from adjuvant CT. A previous analysis of the impact of Oncotype DX® testing in a N1 BC population from 2 Irish cancer centres identified a 55% reduction in CT use with savings of over €1 million. In this study, we have extended the analysis to 5 Irish cancer centres. The objectives of this study were to examine the clinical and economic impact of Oncotype DX testing on treatment (tx) decisions in N1 patients at a national level with a larger patient (pt) population, and to examine changes in the ordering of Oncotype DX tests pre and post RxPONDER data. Methods: From November 2012 to October 2022, a retrospective, cross-sectional observational study was performed of HR+, HER2-, N1 pts who had Oncotype DX testing across five of Ireland’s BC centres. All pts with N1 disease were assumed to be recommended adjuvant CT pre-Oncotype DX testing. Using RxPONDER risk groupings, pts were classified into low risk (RS 0-13), intermediate risk (RS 14-25) and high risk (RS 25). Data was collected via electronic pt records and clinical chart review. Information regarding costing was provided by the National Healthcare Pricing Regulatory Authority and the economic analysis was adjusted for changing costs over the study time-period. RxPONDER was presented at SABCS December 2020. We compared the changes in the demographics of Oncotype DX test ordering and CT prescribing from 2019 – 2020 and 2021 – 2022. Results: 828 pts were included in this study. Mean age was 58 years (range 22-81). Median tumour size was 2.28cm (range 0.3-12.5cm), and 92 (11%), 530 (64%) and 206 (25%) had grade 1, grade 2, and grade 3 disease, respectively. 319 (38%) had RS 0-13, 396 (48%) RS 14-25 and 113 (14%) RS 25. 378 pts (46%) had 1 LN+, 126 (15%) 2 LN+ and 47 (6%) 3 LN+. 277 pts (33%) had micro-metastatic disease only. No association between the numbers of nodes affected and RS result was identified. 171 pts (21%) were 50 years at diagnosis; 54 (32%) had RS 0-13, 89 (52%) RS 14-25 and 28 (16%) RS 25. Post Oncotype DX -testing, 480 pts (58%) had a change in tx decision; 446 (54%) were prescribed hormone therapy (HT) alone and 34 (4%) prescribed HT and ovarian function suppression. In total 348 pts (42%) were recommended adjuvant CT; 48 (14%) RS 0-13, 191 (55%) RS 14-25 and 109 (31%) RS 25. Of 171 pts age 50, 60 (35%) avoided CT. Use of the RS assay was associated with a 58% reduction in CT administration overall. This resulted in savings of over €6 million in tx costs. Deducting the assay cost, net savings of over €3.3 million euro was achieved. Changes in the ordering demographics of RS tests were identified after RxPONDER data was presented. Between 2019 and 2020, 150 tests were ordered, 50 (33%) for pts 50. Between 2021 and 2022, 271 tests were ordered, 47 (17%) for pts 50, corresponding to a 48% reduction in the proportion of Oncotype DX tests ordered for pts 50. We also observed a change in CT recommendation for pts 50; a 40% reduction in CT administration in the pre-RxPONDER time-period fell to 21% post RxPONDER. Conversely, in pts ≥ 50, we identified less CT administration; whereas 60% of pts avoided CT pre RxPONDER, 71% of pts avoided CT post RxPONDER. This indicates increasing confidence in this genomic test for postmenopausal women with N1 disease. Conclusions: Ireland was one of the first public healthcare systems to approve reimbursement for Oncotype DX testing in both N0, and N1 pts. Between 2012-2022, assay use resulted in a 58% reduction in CT administration and net savings of over €3 million. The presentation of RxPONDER has led to reduced Oncotype DX testing in premenopausal patients and increased testing in postmenopausal women. Citation Format: Iseult Browne, Ronan McLaughlin, Catherine Weadick, Shane O'Sullivan, Steve Millen, Danial Hadi, Syed Bilal-Shah, Maha Al Sendhi, Michaela Higgins, John Crown, Ruth Prichard, Damian McCartan, Arnold Hill, Roisin Connolly, Sinead Noonan, Deirdre O'Mahony, Ciara O'Hanlon-Brown, Bryan Hennessy, Cecily Quinn, Catherine M. Kelly, Seamus O'Reilly, Patrick G. Morris, Janice Walshe. Irish National Analysis of the Clinical and Economic impact of 21-gene Oncotype DX® testing in Early-Stage, 1-3 lymph node positive, Hormone Receptor positive (HR+), HER2-Negative (HER2-), Breast Cancer (BC) 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 PO5-02-04.