LAUSR

Introduction: The SEER Program of the NCI is an authoritative source of cancer incidence and survival statistics. Linking the 21-gene assay Recurrence Score® (RS) results to the SEER Registries (N=44,825) demonstrated very low 5-year breast cancer-specific mortality (BCSM) with RS Methods: Patients were eligible if node negative (N0), HR+, HER2-negative (by RT-PCR), had no prior malignancy, had poorly differentiated (G3) tumors, and were diagnosed between Jan 2004 (test available in Jan 2004) and Dec 2011 (SEER survival updated through 2012). BCSM was defined according to pre-existing robust methodology (J Natl Cancer Inst. 2010;102:1584). RS was categorized according to the cutpoints of 18 and 31 established in the NSABP B-14 study. Five-year BCSM was estimated using actuarial methods. Results: Among 6,666 eligible patients with G3 tumors, 4,683 had tumors ≤2 cm and 1,983 had tumors >2 cm. Median age was 57 years; 99.1% were female. Median follow-up was 39 months. The proportion of patients with RS 2 cm, somewhat lower than the overall population. For RS 2 cm); reported chemotherapy use was 10% and 16%, respectively. 5-year BCSM for all groups are provided in Table. An additional year of BCSM follow-up in N0 G3 disease, as well as results for patients with node positive (micrometastases or 1-3 positive nodes) G3 disease, will be available for presentation. Conclusions: Although patients with poorly differentiated tumors have worse prognosis in general, the RS identifies a sizable proportion of patients who can expect good outcomes without chemotherapy and its associated toxicity. Citation Format: Petkov VI, Miller DP, Howlader N, Baehner FL, Penberthy L, Shak S. SEER study of breast cancer-specific mortality in patients with poorly differentiated tumors treated based on recurrence score results [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD7-06.