e12754 Background: Despite widespread adoption of the 21-gene Recurrence Score (Oncotype DX RS) to guide adjuvant chemotherapy in early-stage HR+/HER2- breast cancer, real-world practice shows substantial chemotherapy use without genomic testing, relying on clinician judgment and clinicopathologic features. Prior studies show RS identifies low-risk patients who can safely omit chemotherapy, but comparative survival among chemotherapy-treated patients by RS-guided vs clinician-guided decisions remains underexplored. Methods: Using NCDB (2010–2022), we identified adult women with resected T1b–T2 N0 HR+/HER2- breast cancer who received adjuvant chemotherapy and endocrine therapy (excluding neoadjuvant therapy or missing key data). RS-guided chemotherapy (RS-CT) was defined as chemotherapy with RS > 26, and clinician-guided chemotherapy (Clin-CT) as chemotherapy based on clinician judgment without a documented RS record. Baseline differences were assessed by standardized mean differences (SMD). Overall survival (OS) was evaluated with Kaplan–Meier and stabilized inverse probability of treatment weighting (IPTW) with weighted Cox models. Absolute differences were quantified using IPCW-restricted mean survival time (RMST). Results: Among 59,247 patients (median follow-up 75.0 months), 28,349 (47.9%) were RS-guided and 30,898 (52.1%) were clinician-guided. IPTW achieved balance (post-weighting SMD 55 years among RS-CT group (HR: 0.870, 95% CI 0.816–0.928, p 55 years and Black patients. These findings suggest that reliance solely on clinicopathologic features for chemotherapy decisions may not optimally identify biologic risk in the treated population, potentially exposing patients to chemotherapy toxicity without commensurate benefit, whereas the Oncotye (RS) based on genomic profiling may identify chemotherapy-eligible patients whose underlying biologic risk is not fully captured by clinicopathologic features and clinician judgment in routine practice.
Han et al. (Thu,) studied this question.