Abstract P5-08-08: Use across Michigan of the 21-gene recurrence score (RS) assay in lymph node positive patients with breast cancer
Authors: Henry NL , Ali H , Braun T , Munir K , Silver SM , Griggs JJ , Breslin TM , Gorski DH 
Published: May 2016

Background: Standard of care for women with lymph node positive breast cancer includes treatment with chemotherapy. The 21-gene RS assay is indicated to assess prognosis and to predict response to adjuvant chemotherapy in patients with early stage hormone receptor-positive, HER2-negative invasive breast cancer. Findings from the SWOG S8814 clinical trial, published in 2010, suggested utility for using the RS assay for treatment decision making in node-positive patients in order to withhold chemotherapy. The Center for Medicare and Medicaid Services subsequently approved coverage for the use of the RS assay in women with up to 3 involved lymph nodes, and the National Comprehensive Cancer Network recently recommended consideration of testing in this population. We examined trends in the use of testing of patients with node positive breast cancer with the RS assay in hospitals across Michigan from 2006 through 2013 using data from the Michigan Breast Oncology Quality Initiative (MiBOQI), a Blue Cross Blue Shield of Michigan/Blue Care Network-sponsored quality initiative.

Methods: Demographic, pathologic, and treatment data for women with breast cancer treated at all 25 hospitals participating in MiBOQI were abstracted from the medical record. Patients were excluded if they had stage 0 or IV disease at diagnosis, received neoadjuvant therapy, had bilateral breast cancer, or had a prior history of breast cancer. The primary endpoint was the percentage of patients with lymph node positive, hormone receptor-positive, HER2-negative breast cancer who underwent testing with the RS assay. Analyses were performed using the statistical software R, Version 3.0.1.

Results: Of the 30,992 patients included in the MiBOQI Registry from 2006-2013, 2526 (10.7%) had hormone receptor positive, HER2 negative, lymph node positive disease and met the eligibility criteria. The rate of testing with the RS assay in this patient cohort increased from 0% in 2006 to 32.5% in 2013, including an increase from 15.4% in 2010 to 28.3% in 2011. Median age of the tested cohort was 60 (range 26-87). On multivariate analysis, testing was statistically significantly associated with older age, smaller tumor size, 1-3 involved lymph nodes, and lower Charlson Comorbidity Index. Receipt of chemotherapy was lower in those patients who underwent testing compared with those not tested (40.0% vs 82.0%, p&lt;0.001). Chemotherapy was administered to 105 (27.4%) of the patients with RS &lt; 18, 91 (51.4%) of the patients with RS 18-30, and 49 (92.4%) of the patients with RS &gt; 30.

Conclusions: Use of the RS assay for assessment of women with involved lymph nodes is increasing over time, primarily in older patients and patients with lower risk disease, and is associated with decreased treatment with chemotherapy. Results of the ongoing SWOG S1007 clinical trial, which is assessing the impact of use of the RS assay on breast cancer outcomes, are eagerly awaited.

Citation Format: Henry NL, Ali H, Braun T, Munir K, Silver SM, Griggs JJ, Breslin TM, Gorski DH. Use across Michigan of the 21-gene recurrence score (RS) assay in lymph node positive patients with breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-08.