21-Gene Recurrence Score and Survival Outcomes in the Phase III Multicenter TAILORx Clinical Trial.

Background: Recurrence score (RS) based on a 21-gene genomic assay is frequently used to estimate risk of distant recurrence for choice of adjuvant chemotherapy in breast cancer. It remains unclear whether RS is an independent prognostic factor for breast cancer-specific survival (BCSS) and overall survival (OS) in the TAILORx trial population.

Methods: We evaluated the association of RS with BCSS and OS plus recurrence-free interval (RFI) and invasive disease-free survival (DFS) using multivariable Cox proportional hazards regression analysis, adjusting for clinicopathologic measures, in 8,916 patients with hormone receptor-positive, HER2-negative, node-negative breast cancer. Likelihood ratio (LR) test was used to assess the relative amount of prognostic information provided by RS to BCSS, OS, RFI, and DFS, comparatively.

Results: Event rates for BCSS, OS, RFI, and DFS were 1.7%, 5.2%, 5.6%, and 12.6%, respectively, by up to 11.6 years of follow-up. Compared with low-range RS (0-10), patients with midrange (11-25) and high-range (26-100) RS had inferior BCSS (adjusted hazard ratio [aHR], 5.12 [95% CI, 2.09-16.92] and 8.03 [95% CI, 2.91-28.47], respectively) and RFI (aHR, 1.68 [95% CI, 1.23-2.36] and 3.05 [95% CI, 2.02-4.67], respectively), independent of clinicopathologic factors. High-range score was associated with an increased risk of DFS (aHR, 1.56 [95% CI, 1.20-2.04]) but not significantly associated with OS (aHR, 1.44 [95% CI, 0.95-2.18]). Midrange score was associated with neither DFS (aHR, 1.15 [95% CI, 0.96-1.38]) nor OS (HR 1.14 [95% CI, 0.87-1.52]). LR-χ2 values were 83.0 and 65.1 for RFI and BCSS, respectively, and 17.5 and 33.6 for OS and DFS, respectively (P<.0001).

Conclusions: RS is an independent measure for BCSS and recurrence prognoses relative to OS in early-stage breast cancer. It carries more prognostic information for breast cancer-specific outcomes.