Abstract PS6-25: Cts5 tested in a Brazilian population: A tool that can predict global survival in early breast cancer ER+/HER2-, as well as the response to extended endocrine therapy

Abstract Background: Breast cancer (BC) accounts for 30% of female cancer, is the most commonly diagnosed cancer worldwide and the second most common cause of cancer-related deaths among females. The majority (79%) of breast cancers express the estrogen receptor (ER+) and 91% of them are diagnosed at an early stage. But it is also known that late recurrence (5 years or more after diagnosis) represents about 50% of all recurrences of ER+ BC. Identify those patients who are at greatest risk for late recurrence and develop strategies to prevent it has emerged as a major unmet need in ER+ BC. In an attempt to reduce late recurrences, several studies have recently proposed that endocrine therapy (ET) prolonged beyond five years would achieve this goal. Conversely, extended ET increases the rates of side-effects, compared to conventional ET. Therefore, selecting patients who would really benefit from extended ET is crucial, as this would spare low-risk patients from potentially greater side effects and impacts in quality of life, restricting the treatment only for those who really could take advantage of this approach. That is why, currently, the subject late recurrence is being studied so much. CTS 5 (Clinical Treatment Score after 5 years) is a simple clinical-pathological tool developed to estimate the residual risk of distant recurrence after 5 years of ET. Objective: To assess the prognostic and predictive impact of CTS5 in overall survival (OS) of ER+BC patients treated with conventional or extended ET in a Brazilian Cancer Center. Study design and statistical analysis: A retrospective cohort study was conducted, selecting, through administrative databases of AC Camargo Cancer Center, 1085 ER+ BC patients with at least 5 years of adjuvant ET. Patients who missed follow-up before completing ET were excluded, but we kept those who presented any event related to illness or treatment. Statistical analysis includes a Kaplan-Meier analysis and the Log Rank test. Prognostic factors were assessed using univariate and multivariate Cox analysis. Results: The demographic and clinical characteristics of patients are described in table 1. In this cohort, continuous CTS5 was a significant predictor for OS (HR = 4,49 [3.12-6.46], p<0.001). In addition, in the high CTS5 group a significant benefit was observed with prolongation of adjuvant ET beyond 5 years (HR = 4,91 [3.41-7.06], p<0.001), not observed for low and intermediate risks. Conclusion: In this cohort, composed of real-life Brazilian women with ER+/ HER2- BC, irrespective of menopausal status, CTS5 proved to be an excellent predictor of OS. In addition, it was shown to be a predictor of response to extended ET. CTS5 score can identify a group of high-risk patients who benefits from extended ET. We consider that it would be of great value to expand the study population and follow-up, especially to analyze whether this tool also has a predictive value in contraindicating extended ET in low- risk and intermediate-risk patients. Table 1. Demographic and Clinical CharacteristicsCharacteristicNo. (%)Age, yearsMedian53IQR26-91< 50 years446 (41.1)>50 years639 (58.9)Tumor size, mm≤ 10285 (24.1)10-20458 (38.7)20-50378 (31.9)>5060 (5.1)GradeWell142 (11,9)Intermediate385 (32,5)Poor654 (55,2)Nodal status (No. of positive nodes)0756 (64.0)1 -3305 (25.8)≥4120 (10.2)ChemotherapyAdjuvant592 (50.1)Neoadjuvant118 (10.0)Endocrine TerapyET 5 years1060 (89,7)ET extendend100 (8.4)ET for less than 5 years.21 (1,8)CTS5Low587 (49.6)Intermediate344 (29.1)High250 (21.1)RecurrenceDistant147 (12,4)Local 39 (3,3) Citation Format: Lucas Vian, Ronaldo Souza, Vladmir Claudio Cordeiro de Lima, Daniella Yumi Tsuji Honda, Samara Theodoro Pacheco, Caio Dabbous de Liz, Luciana Beatriz Mendes Gomes, Bruno Cezar Mendonça Uchôa Júnior, Paula Tavares Guimarães, Celso Silva e Souza Filho, Andréa Paiva Guimarães, Maria Fernanda Evangelista Simões, Mauro Daniel Spina Donadio, Angelo Bezerra de Souza Fêde, Augusto Obuti Saito, Adriana Regina Gonçalves Ribeiro, Joyce Maria Lisboa Maia, Iara Karoline Freire Lustosa, Fabricio de Souza Castro, Monique Celeste Tavares, Marcelle Goldner Cesca, Marcelo Corassa, Noam Falbel Pondé, Solange Sanches. Cts5 tested in a Brazilian population: A tool that can predict global survival in early breast cancer ER+/HER2-, as well as the response to extended endocrine therapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-25.