Breast cancer-specific survival outcomes among patients based on 21-gene recurrence score.

Abstract

537 Background: The 21-gene recurrence assay predicts cancer recurrence rates and benefit from adjuvant chemotherapy among patients with hormone-receptor-positive breast cancer. The National Cancer Institute and Genomic Health collaborated to provide Recurrence Score (RS) results to complement data from 17 population-based cancer registries in the Surveillance, Epidemiology, and End Results (SEER) Program. Methods: Using the SEER database with linked RS results, a cohort of female breast cancer patients, age greater than 20 years, was identified by RS (low: < 18, intermediate: 18-30, high: > 30) diagnosed between the years 2004 and 2007. A retrospective analysis was conducted to determine eight-year breast cancer-specific survival rates based on RS and other variables. Results: 10,318 patients were identified in the cohort. 5,194 had a low risk RS; 4,282 had an intermediate risk RS; 872 had a high risk RS. Histologic subtypes were: 7,459 infiltrating ductal carcinoma, 941 mixed infiltrating and lobular carcinoma, 933 lobular carcinoma, 327 mixed infiltrating ductal and other histology, 244 mucinous adenocarcinoma, 101 tubular adenocarcinoma, 45 mixed lobular and other histology, 268 other histologies. 644 low risk RS patients received chemotherapy (12.4%); 1,608 intermediate risk RS patients received chemotherapy (37.8%); 593 high risk patients received chemotherapy (68.0%). The eight-year breast cancer-specific survival rates (with 95% confidence intervals) among low risk RS patients without known chemotherapy administration was 98.9% (98.5, 99.2), and 98.4% (97.0, 99.1) with chemotherapy; intermediate risk RS patients without known chemotherapy was 97.0% (96.2, 97.6), and 96.9% (95.9, 97.7) with chemotherapy; high risk RS patients without known chemotherapy was 89.7% (85.4, 92.8), and 92.9% (90.4, 94.7) with chemotherapy. Conclusions: Among a large cohort of patients identified in a population-based cancer registry between 2004 and 2007, there was no statistically significant difference in eight-year breast cancer-specific survival rates among those who received chemotherapy and those who did not, regardless of RS risk group.