Long-Term Prognostic Value and Analytical Parameters of the Next-Generation Sequencing-Based Multigene Assay in Hormone Receptor-Positive, HER2-Negative Breast Cancer

In hormone receptor (HR)-positive, HER2-negative early breast cancer, gene expression testing facilitates treatment decisions. A next-generation sequencing (NGS)-based assay was developed to address test decentralization and underrepresentation of younger/premenopausal patients. We aimed to validate the long-term prognostic value of the NGS-based assay and analyze its quality control (QC) parameters. We analyzed samples from 265 patients with breast cancer with at least 10 years of follow-up. We evaluated the long-term prognostic ability of the NGS-based assay according to the risk groups for distant recurrence, as determined by the Decision Index (DI), and the performance of the QC parameters used for the experimental process. Among 265 participants, 60.4% were ≤50 years old, and 39 (14.7%) experienced distant recurrence within 10 years. In the DI-stratified low- and high-risk groups (n=186; 70.2% and n=79; 29.8%), 10-year distant metastasis-free survival rates were 96.1% (95% CI 92.1-98.1) and 79.3% (95% CI 68.4-86.8), respectively. In patients aged ≤50 years, the high-risk group had a hazard ratio of 5.89 (95% CI 2.84-12.20). Analyses including 106 samples that failed the stringent QC criteria showed inferior prognostic value, wherein DV200 and cDNA concentrations were the most crucial parameters. We validated the prognostic ability of an NGS-based assay to stratify HR-positive/HER2-negative breast cancers and predict the risk of distant recurrence, and confirmed the requirement for stringent QC criteria to ensure its prognostic ability.