Abstract PO1-28-03: Impact of the Oncotype DX® test over time and association with clinicopathological characteristics of Peruvian patients with early breast cancer: Experience in the last 15 years

Abstract

Abstract Introduction: Gene expression assays provide prognostic and therapy-predictive information that complements management of early breast cancer patients. Oncotype DX® had showed prognostic and prediction of adjuvant chemotherapy benefit. The present study evaluates the impact of Oncotype DX® on therapeutic decision-making for 15 years and explores the association of clinicopathological characteristics with the Recurrence Score (RS) in Peruvian patients with early breast cancer. Material and methods: A retrospective multicenter analysis of 759 breast cancer patients treated in three oncological centers in Lima-Peru (Instituto Nacional de Enfermedades Neoplásicas, Oncosalud and Ricardo Palma) between 2007 and 2022 was conducted. Risk groups were classified according to Oncotype DX® result and menopausal status. For premenopausal women ≤ 50 years: low (RS=0-20), intermediate (RS=21-25) and high-risk (RS=26-100). A descriptive analysis was evaluated to observe the trend and profile of the patients who used the Oncotype test in 5 time periods (2007-2009, 2010-2013, 2014-2016, 2017-2019, 2020-2022). Subsequently, chi-square, t-test, analysis of variance and Poisson linear regression tests were applied to compare clinicopathological features with RS. Finally, univariate and multivariate analyses were performed using Cox logistic regression to identify the probability of association with the high-risk group. Results: 642 patients were included, 78.5% were postmenopausal, and 64.2% had clinical stage (CS) I. Overall, 63.4% had no recommendation for chemotherapy and only 5.6% had recurrence. 74.8% were classified as low-risk according to the Oncotype DX® result. Postmenopausal patients had negative lymph nodes (95.4%), the majority had undergone conservative surgery (71.8%) and had a low rate of breast reconstruction (11.9%). An increase in the use of Oncotype DX® was observed over time, especially in premenopausal patients (from 4.5% in 2007 to 36.9% in 2022). A significant association was found between luminal B subtype (p < 0.0001), histological grade 3 (p < 0.0001) and T3 vs. T1/2 (p=0.025). In univariate analysis, luminal B subtype (vs. luminal A, OR=5.56, 95% CI, 2.80-12.3, p< 0.001), T3 (vs. T1/2, OR=2.84, 95% CI, 0.13-30.0, p=0.006), histological grade 3 (vs. 1/2, OR=13.1, 95% CI, 5.35-39.6, p< 0.001) and histology (other vs. ductal/lobulillar/mucinous, OR=2.94, 95% CI, 0.57-13.5, p=0.003) provided a higher probability of obtaining a high-risk RS result. Similar results were found in multivariate analysis. Conclusion: The use of the Oncotype DX® had a significant impact on therapeutic decision-making in Peruvian patients with early breast cancer, with an increase of use in the last 15 years. A high-risk RS was associated with luminal B subtype, histological grade 3 and T3 tumor size, which could facilitate risk stratification and provide valuable information for the need of adjuvant chemotherapy. Keywords: Early breast cancer, Oncotype DX®, clinicopathological characteristics, Recurrence Score (RS), Peru Oncotype PERU Table Citation Format: Steffi Katheryne Gonzalez Bocanegra, Guillermo valencia Mesías, Yomali Aroa Ferreyra Chombo, Karoll Tatiana Meza Garcia, Mariano Lopez-Pereyra, Jorge Torres Maldonado, Edgar Fermín Yan Quiroz, Zaida Morante Cruz, Jose Cotrina-Concha, Henry Gómez, Gabriela Calderon Valencia, Mauricio León Rivera. Impact of the Oncotype DX® test over time and association with clinicopathological characteristics of Peruvian patients with early breast cancer: Experience in the last 15 years [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 PO1-28-03.