138P Predicted cumulative risk of late relapse in HR-positive/HER2-negative BC: A competing risk analysis of a real-world population

The risk of relapse in patients with hormone receptor (HR)-positive, HER2-negative breast cancer (BC) is known to only partially subside over time, persisting up to 20 years from diagnosis. An extended duration of endocrine therapy (ET) significantly reduces this risk. We aimed to describe the cumulative incidence of distant relapse (DR) and local relapse (LR) in a population of intermediate/high risk BC patients from real-world dataset with a long follow up. Our analysis is based on a dataset including 941 patients diagnosed with early HR-positive BC between 2000 and 2007 at a large tertiary-level cancer center in Italy. Statistics were based on a competing risks regression model based on cause-specific proportional hazards, where LR and DR were considered competing events. The model was extended with intermediate states determined by initiation and termination of ET and the inclusion of duration of ET as a time-dependent covariate, among many other covariates under study. Here we present the predicted cumulative incidence of DR and LR at 10 years for a patient at intermediate/high clinical risk who had completed at least 8 years of ET. Intermediate/high risk was defined as N1 disease or tumor larger than 2 cm. Median age was 56 years. About 12% of the patients had N0 with a tumor diameter of 2 cm or more, while nodal involvement was reported in 40% of the patients. More than 60% received chemotherapy. The median follow-up was 152 months. Main results are reported in the table.Table: 138PPredicted cumulative incidence of DR and LR at 10 years after 8 years of ETStageDRLRG2G3G2G3pT1N16.2 (0.2-28.5)7.2 (0.3-29.6)10.6 (2.7-24.9)7.7 (1.9-19.3)pT2N02.3 (0.1-13.6)7.5 (0.3-32.1)4.6 (1-12.8)3.5 (0.6-10.7)pT2N19.1 (0.1-42.4)13.6 (0.48-47.4)5.9 (1.1-17)4.3 (0.8-12.8) Open table in a new tab Long term incidence of distant or local relapse remain an unmet need, even in patients treated with extended ET. Biological factors as TN status and grade have an impact on late relapse.