Abstract P1-04-15: Clinical application of 21-gene breast-cancer assay (Oncotype DX) in early hormone-receptor–positive, human epidermal growth factor receptor 2 (HER2)–negative breast cancer with Lymph-Node-Positive Disease

Abstract The 21-gene breast-cancer assay (Oncotype DX) has become widely available since 2011 and it is incorporated in treatment guidelines for early hormone-receptor–positive, human epidermal growth factor receptor 2 (HER2)–negative breast cancer. The Rxponder trial shows the role of adjuvant chemotherapy in node positive patients with a RS score less than 25, but in patients under 50 years of age benefit from adjuvant chemotherapy treatment regardless of the Oncotype. We analyzed our results of the Oncotype Dx in 317 node positive hormone-receptor–positive, HER2-negative early breast cancer patients, performed as a clinical practice since 2015 to 2020. The aims to current study are to examine the clinical significance of the oncotype Dx results in this specific population. The median age was 59 years with 102 patients (32%) less than 50 years. Median Oncotype DX score was 18 ( 1–68), RS< 25 in 247 (78%) and RS>25 in 70 (22%) patients. Median initial tumor size was 20 mm and the expression of classical biological variables was: median estrogen and progesterone receptors by immunohistochemistry 276 and 139 respectively and median Ki67 index was 23%. 145 patients received chemotherapy treatment (45,7%), (RS < 25:32%, RS>25: 94%) with a 63% of the patients in the group less than 50 years of age in contrast to 36% in patients with more than 50 years. Patients with more than 50 years have less RS score (median 18 ) than patients less than 50 years (median 21 ). With a median of follow up of 45 month with achieved a total of 29 recurrence (9,1%), RS< 25: 8% and RS>25 13%. The estimated median disease free survival of patients with RS< 25 was 111 in contrast to 97 in patients with RS>25 (log rangk : p:0,035) and without differences according with age of the patients. In axillary node positive patients, Oncotype Dx could avoided chemotherapy in 55% of patients, with a index of recurrence of 9%. Patients with a RS score greater than 25 have a higher rate of recurrence (13%) despite the fact that the majority (94%) received treatment with chemotherapy. Improve adjuvant treatment is needed in patients with a score greater than 25. Citation Format: Ariadna Gasol Cudós, Serafin Morales Murillo, Noemí Tuset Der-Abrain, Ana Velasco Sánchez, Felip Vilardell Villellas, Douglas Sánchez Guzmán, Carles Canosa Morales, Jordi Melé Olivé, Laura Arbones Cid. Clinical application of 21-gene breast-cancer assay (Oncotype DX) in early hormone-receptor–positive, human epidermal growth factor receptor 2 (HER2)–negative breast cancer with Lymph-Node-Positive Disease [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 P1-04-15.