Factors associated with 21-gene assay receipt among women with lymph node positive breast cancer.

Abstract

6554 Background: The 21-gene Breast Recurrence Score (RS) assay predicts breast cancer (BC) recurrence and adjuvant chemotherapy benefit in select patients with lymph node-positive (LN+), hormone receptor-positive (HR+), HER2 negative BC. This study examines factors associated with assay uptake among women with LN+ BC in SEER databases. Methods: In this population-based study, incident BC cases in SEER registries (2010-2013) were linked to RS results from assays performed by Genomic Health. Our study sample included women with non-metastatic, LN+ (≥1 positive LN), HER2-, HR+, BC. We use logistic regression to identify demographic, SES, and tumor characteristics associated with having the 21-gene assay ordered. Results: A total of 4428 (14.0%) of 31520 women with LN+, HR+, HER2-, BC had the assay ordered. Uni- and multi-variate analyses identified key factors that were significantly associated with the proportion of women tested. In the multivariable analysis, age (aOR: 2.23, p<0.001, 65-74 v <45 years) and BC diagnosis year (aOR:1.75, P<0.001 2013 vs 2010) were positively associated with assay receipt; whereas number of positive LN (aOR: 0.14, p<0.001, 4+ positive LN vs 1 positive LN), tumor grade and size, low SES, being black, and being widowed were negatively associated with assay uptake (p<0.001). Having Medicaid was associated with lower odds of test receipt (p=0.01). Finally, we identified geographic variation in assay ordering. See univariate results (Table). Conclusions: Important demographic and SES variables were associated with test receipt in LN+ disease, and differed from those previously reported in node negative disease. Moving forward, increased awareness of these disparities, particularly among low SES, Medicaid, Black and widowed patients, along with targeted interventions may help to improve quality of care and equity in test receipt. [Table: see text]