Comparing the Combination of Clinical Risk and Ki-67 Using EndoPredict as an Alternative to Multigene Assays in Prognostic Evaluation of Breast Cancer.

Purpose: Many studies have examined the relationship between prognostic factors and multigene assays; however, their use as alternatives remains insufficient. This study evaluated the concordance of the combination of clinical risk (CR)-which was determined using the modified version of Adjuvant! Online-and the Ki-67 index using EndoPredict (EP).

Methods: Retrospective data from 709 patients were analyzed. The diagnostic accuracy, including concordance, was assessed between CR and EP (EPclin risk vs. EP risk), along with the Ki-67 index (cut-off: 20%). The clinical significance was analyzed using an area under the receiver operating characteristic (ROC) curve.

Results: EPclin risk showed higher concordance with both CR and Ki-67 than EP risk, and CR showed higher concordance with both EPclin and EP risk than Ki-67. Differences in concordance with CR based on Ki-67 were limited; however, the negative predictive value (NPV) increased in the Ki-67 < 20% group (86.9% in EPclin), whereas the positive predictive value (PPV) increased in the Ki-67 ≥ 20% group (82.7% in EPclin). Improvement in PPV and NPV, as well as concordance, was observed with EPclin in 447 patients with high CR/high Ki-67 and low CR/low Ki-67. ROC analysis confirmed the clinical significance of combining CR with the Ki-67 index, as their combined area under the curve increased to 0.794, compared to 0.660 for CR and 0.742 for Ki-67 alone in EPclin risk.

Conclusion: Integrating CR with the Ki-67 index improves prognostic accuracy and provides a cost-effective alternative to the EP test for luminal-type early breast cancer.