Abstract PS3-10-06: Comparison between the LRP model and Adjuvant! Online in predicting 9-year distant disease-free survival

Abstract Background: MammaTyper® is a RT-qPCR kit that quantitatively detects the mRNA level of the four genes ESR1, PGR, ERBB2, and MKI67 in breast cancer FFPE tissue. The MammaTyper® Low Risk Prediction (LRP) model has demonstrated high predictive value for identifying Oncotype DX Recurrence Score (ODX-RS) <=25 in patients with T1-2, N0-1, ER+/HER2− breast cancer. However, the prognostic value of the LRP model remains unclear. This study aims to compare the prognostic performance of the LRP model with Adjuvant! Online in predicting distant disease-free survival (DDFS). Methods: This retrospective study included women diagnosed with T1-2, N0-1, ER+/HER2- BC who received ET±CT between 2014 and 2018 at Peking University First Hospital. After laboratory testing with MammaTyper®, the LRP model was applied in this cohort (Available online at: https://mtrg-ruo.com/LRP). A modified version of Adjuvant! Online was used to determine clinical risk groups. DDFS was compared using log-rank tests and Cox proportional hazards models. Results: A total of 352 samples were successfully classified into clinical high-risk (C-high) and low-risk (C-low) groups by the modified version of Adjuvant! Online, and into LRP high-risk (LRP-high) and low-risk (LRP-low) groups using the MammaTyper® LRP model. The median follow-up time was 85 months. The LRP model showed greater statistical significance in differentiating low-risk from high-risk groups in terms of 9-year DDFS compared to Adjuvant! Online (log-rank p = 0.0015 for the LRP model vs. log-rank p = 0.016 for Adjuvant! Online). Patients were categorized into four combined risk groups: C-low/LRP-low (33.5%, 118/352), C-low/LRP-high (15.9%, 56/352), C-high/LRP-low (23.3%, 82/352), and C-high/LRP-high (27.3%, 96/352). Patients in the C-low/LRP-low group had the highest 9-year DDFS rate of 97.3% (95% CI: 94.3-100.0%), whereas the lowest rate of 81.3% (95% CI: 70.6-93.6%) was observed in the C-high/LRP-high group. Patients in the C-high/LRP-low group did not show a significant benefit from adjuvant chemotherapy in terms of DDFS (HR = 0.33, 95% CI: 0.03-3.65). Conclusions: The MammaTyper® LRP model is comparable to Adjuvant! Online in predicting 9-year DDFS in patients with T1-2, N0-1, ER+/HER2- breast cancer treated with ET ± CT. No significant DDFS benefits was observed from adjuvant chemotherapy in patients classified as C-high/LRP-low. Our results suggest that MammaTyper® may be useful as a locally available kit for identifying ER+/HER2- BC patients with low risk of recurrence. Citation Format: M. Ding, H. Zhang, Q. Wu, Y. Cheng, L. Xu. Comparison between the LRP model and Adjuvant! Online in predicting 9-year distant disease-free survival [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-10-06.