Abstract P2-11-18: Clinical validity of CTS5 for late recurrence in Chinese patients with early HR-positive breast cancer
Authors: Xu Junnnan , Sun Tao 
Published: March 2020

Abstract
Objective: The large majority of hormone receptor-positive (HR+) breast cancer patients will be treated with hormone therapy at least five years to decrease the risk of cancer recurrence or distance metastases. EBCTCG meta-analysis identify extending endocrine therapy could further late recurrence for some patients, however, accompanying with more side effects. Estimating risk of late distant recurrence (DR) is an important goal for managing women with HR+ breast cancer after 5 years of endocrine treatment without recurrence. New research confirms that an algorithm, called CTS5, can accurately identify patients who are at a significantly low risk of their breast cancer returning at a later stage in ATAC and BIG1-98 cohort. The aim of this study was to investigate the predictive value of CTS5 in Chinese HR+ early breast cancer.
Patients and Methods: The CTS5 was tested in a retrospective cohort of breast cancer from Liaoning Cancer Hospital between 2002 and 2009. Among 831 patients with distant recurrence-free and be alive at 5 years, the patients were tested and calculated for CTS5, a prognostic score for post-5-year risk of DR, in HR+ early breast cancer after adjuvant endocrine therapy. The cut-off values for separate the risk category were 3.13 and 3.86 from the final CTS5 in ATAC and BIG1-98. The primary end point was distant recurrence in years 5~10 in HER-2 positive and HER-2 negative cohorts.
Results: Continuous and categorical CTS5 score was significantly prognostic for late DR for total sample (n=831) and HER-2 negative cohorts (n=634). CTS5 (based on ATAC/BIG1-98 data) risk stratification defined in the total cohort as low (&lt; 5% DR risk, years 5 to 10), intermediate (5% to 10%), or high (&gt; 10%) identified 35.0% of our cohort as low risk (291/831), 28.52% as intermediate risk (237/831) and 36.46% as high risk (303/831). In HER-2 negative data, CTS5 risk stratification defined in the 634 cohort from 2002 to 2009 as low risk with an observed DR rate of 6.15% during years 5 to 10, intermediate risk with an observed DR rate of 11.24% and high risk with an observed DR rate of 28.78%. CTS5 stratifies HER2-negative cohort into three distinct risk groups with higher observed DR than that in ATAC/BIG1-98 trial, however, the separation was less accurate in HER2-positive cohort than in HER2-negative cohort. The observed DR rate was 25.81% in low, 27.94% in intermediate and 37.76% in high groups in HER2-positive cohort. From years 5 to 10, 63% of node-negative patients were low risk, with a DR rate of 5.7% (14/245).
Conclusion: The study confirmed that CTS5 was effective at predicting late recurrence of breast cancer after 5 years in Chinese cohort. However, higher observed rate was indicated due to the bias of the majority from Department of Medical Oncology rather than Department of Breast Surgery. Further large-sample study was designed to validate CTS5 in low-risk and intermediate groups with similar endocrine therapy.
Citation Format: Junnnan Xu, Tao Sun. Clinical validity of CTS5 for late recurrence in Chinese patients with early HR-positive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-11-18.