Abstract P1-06-03: Breast cancer-specific survival (BCSS) in SEER patients with 21-gene Recurrence Score® (RS) results <11 classified as prognostic stage IA by new 8th edition AJCC staging manual

Abstract

Abstract Introduction: The 8th edition of the AJCC Staging Manual added molecular features for the first time and now includes ER, PR, HER2, and the 21-gene assay for prognostic staging. We obtained real-world evidence of BCSS by age, tumor size, and grade in a population-based SEER analysis of N0, HR+, HER2-negative breast cancer and RS <11 (tumor size up to 5 cm) to obtain more detailed information on clinically “unfavorable” subgroups. Methods: RS results were provided to SEER registries as mandated by their methods for linkage (Petkov npj Breast Cancer 2016). Patients (pts) with RS <11 and size up to 5 cm were eligible if N0, HR+, HER2-negative, had no prior malignancy, and were diagnosed between Jan 2004 and Dec 2012 (SEER survival updated through 2013). 5-year BCSS was estimated using actuarial methods. Results: 9,304 pts had RS <11 (19% of those meeting all other eligibility), with median follow-up of 40 months. Median age was 59 y, with 22% <50 y and 16% ≥70 y. Tumor size was >2 cm in 21% of pts. Tumor grade was moderate in 54% and poor in 8% of pts. Overall, 5-year BCSS for pts with RS <11 was 99.6% (95% CI 99.4%, 99.7%), with reported chemotherapy (CT) use in 3.3% of pts. In contrast, BCSS for pts with RS >25 and RS ≥31 was 3.5% and 4.7%, respectively, with frequent CT use. 5-year BCSS for important clinicopathologic subgroups show high 5-year BCSS despite “unfavorable” age, tumor size, and grade (Table). 5-y BCSS for RS <11, by Clinicopathologic FactorsRS <11 and Age <50 yRS <11 and Tumor Size 2.1-5.0 cmRS <11 and Poor Tumor GradeN (% of N with CT ‘Yes’)5-y BCSS (95% CI)N (% of N with CT ‘Yes’)5-y BCSS (95% CI)N (% of N with CT ‘Yes’)5-y BCSS (95% CI)2009 (6.2%)100% (100%, 100%)1976 (5.5%)99.3% (98.5%, 99.7%)686 (5.8%)99.5% (97.9%, 99.9%) Conclusions: In this SEER population-based study, pts with RS <11 had a wide range of clinicopathologic features. 5-year BCSS was high (>99%), regardless of age, tumor size, or grade. These results support the new AJCC staging criteria that classify N0, HR+, HER2-negative pts with RS <11 and tumor size up to 5 cm as having Prognostic Stage IA disease. Citation Format: Baehner FL, Petkov VI, McCullough D, Shak S. Breast cancer-specific survival (BCSS) in SEER patients with 21-gene Recurrence Score® (RS) results <11 classified as prognostic stage IA by new 8th edition AJCC staging manual [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-06-03.