Abstract P4-09-29: PR status cannot predict Oncotype DX Recurrence Score®: a study in a Greek cohort of N0M0/ER+/PR-/HER2- breast cancer patients tested with Oncotype DX

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Abstract Background: The Oncotype DX assay is a widely utilized genomic test that helps predicting the risk of breast cancer recurrence and the potential benefit of chemotherapy in early-stage, hormone receptor-positive (HR+) breast cancer patients. Low/absent expression of PR in ER-positive breast tumors is associated with more proliferative and aggressive disease, poorer prognosis and recurrence. However, the predictive value of progesterone receptor (PR) status in determining chemotherapy benefit remains unclear. This study focuses exclusively on PR-negative breast cancer patients to assess whether PR status can predict chemotherapy benefit using Oncotype DX scores. Methods: We retrospectively analyzed data from a Greek cohort of pT1-3N0, cM0/ER+/PR-/HER2- breast cancer patients who underwent Oncotype DX testing between 2008 and 2020. Patients were categorized based on their Oncotype DX recurrence scores (RS) into low (0-25) and high (>25) risk groups. Results: A total of 268 PR-negative, ER+/HER2- patients were included in the analysis. The mean RS was 20.3. (Mean RS reported in TailorX study regardless of PR status was 18.2). RS 0-25 was reported in 130 (48,5%) of them, while 138 (51,5%) had a RS >25. Conclusion: In PR-negative, pT1-3N0, cM0/ER+/HER2- breast cancer patients, PR status alone does not predict the RS and hence, the benefit of chemotherapy. The Oncotype DX assay effectively stratifies these patients, highlighting those with high RS (>25) who will benefit from chemotherapy. These findings underscore the importance of using Oncotype DX scores rather than PR status alone to guide chemotherapy decisions in PR-negative breast cancer patients. Citation Format: Vasileios Venizelos, Rodoniki Iosifidou, Christos Markopoulos, Gregory Xepadakis, Nikolaos Tsoulos, Spiridon Giannoulakis, Georgios Kapetsis, Amanta Psyrri, Zacharenia Saridaki, Ioannis Natsiopoulos, Adamantia Nikolaidi, Aikaterini Savvidou, Anastasios Mpoutis, Ioannis Mpoukovinas, Athanasios Kotsakis, Athina Christopoulou, Emmanouil Saloustros, Dimitrios Mavroudis, Sofia Aggelaki, Avraam Assi, Dimitrios Tzanninis, Dimitrios Grosomanidis, Elena Fountzila, Efthalia Lala, Eeleftheria Ignatiadou, Maria Skondra, Flora Zagouri, Anna Koumarianou, Paris Kosmidis, Stergios Douvetzemis, Konstantinos Papazisis, Kornilia Anastasakou, Foteini Pavlidou, Eleftherios Kampletsas, Fiorita Poulakaki, Georgios Simpilidis, Sofia Triantafillidou, Maroulio Stathoulopoulou. PR status cannot predict Oncotype DX Recurrence Score®: a study in a Greek cohort of N0M0/ER+/PR-/HER2- breast cancer patients tested with Oncotype DX [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P4-09-29.

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