The Added Prognostic Value of Oncotype Recurrence Score to AJCC Prognostic Staging System in Stage III ER+/HER2− Breast Cancer

Introduction Prognostic prediction based on prognostic stage (PS) with the Oncotype DX recurrence score (RS) has not been validated in stage III ER+/HER2− breast cancer. This study aimed to evaluate the added prognostic significance of RS incorporated with the PS system and to compare the prognostic prediction improvement with anatomic TNM stage (AS) using nomogram construction. Methods The SEER database was indexed to identify ER+/HER2− invasive ductal or lobular breast cancer in AS IIIA–IIIC with RS results diagnosed from 2004 to 2013. Patients with RS < 18, 18–30 and > 30 were categorized into low-, intermediate- and high-risk RS groups. Comparisons of the distribution of clinical-pathologic characteristics among RS risk groups were performed using Pearson's chi-square test. Breast cancer-specific survival (BCSS) was estimated using the Kaplan-Meier method and compared across RS or PS by log-rank test. Cox regression was used to evaluate the factors independently related to BCSS. A nomogram comprised of PS and RS was constructed with discrimination, calibration and clinical benefit evaluated. Results Altogether 629 patients who received RS were enrolled. There were 326 cases (51.8%) with low-risk RS, 237 (37.7%) with intermediate-risk RS and 66 (10.5%) with high-risk RS; 344 patients (54.7%) had PS IB, 84 (13.4%) had IIB, 150 (23.8%) had IIIA, 46 (7.3%) had IIIB, and only 5 had (0.8%) IIIC. Both PS and RS were independent prognostic factors for BCSS. There were significant or trends of differences in survival among RS within subtypes stratified by PS. There were significant differences in survival among PS only within intermediate-risk RS. A nomogram prediction 5-year BCSS was constructed with a c-index of 0.811. Lower histologic grade, positive PR and fewer positive lymph nodes were independently correlated with low-risk RS. Conclusion PS incorporated with RS had improved prognostic significance for stage III ER+/HER 2− breast cancer.