Abstract P5-08-07: Appropriate use of the 21-gene recurrence score (RS) assay across Michigan
Authors: Ali HY , Munir K , Braun T , Griggs JJ , Silver SM , Gorski DH , Breslin TM , Henry NL 
Published: May 2016

Background: The 21-gene RS assay is used to assess prognosis and to predict response to adjuvant chemotherapy in patients with early stage hormone receptor positive, Her2 negative invasive breast cancer. The National Comprehensive Cancer Network (NCCN) first recommended consideration of testing of appropriate patients with the RS assay in 2008. We examined trends in the use of testing 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 outcome was the percentage of patients eligible for testing according to NCCN criteria (version 2010) who underwent testing with the RS assay. Analyses were performed using the statistical software R, Version 3.0.1.

Results: Of the 18,046 patients in the MiBOQI Registry from 2006-2013 who met inclusion and exclusion criteria, 7133 (39.5%) met the NCCN criteria for testing (eligible). The rate of testing increased from 2006 to 2013 in both the eligible and ineligible cohorts, and varied by site.

21-Gene Recurrence Score (RS) Testing in MiBOQI, 2006-2013FactorEligible (n=7133)Ineligible (n=10913)Tested with RS assay3920 (55.5%)1424 (13.0%)Testing rate in 200643.8%7.3%Testing rate in 201362.3%19.6%Testing by site, 2006-2013 (range)35.8% - 73.3%6.8% - 26.2%

Testing of the eligible cohort was statistically significantly associated with younger age, lower tumor grade, and lack of nodal involvement. Overall, 73.4% of patients whose tumors were tested with the RS assay met the NCCN criteria for testing and were deemed appropriately tested. This rate of appropriate testing ranged from 60.8% to 85.4% across sites. Of all patients who underwent testing, 498 (9.3%) had 1 or more positive lymph nodes (&gt;0.2 cm). Receipt of chemotherapy was lower in eligible patients who were tested compared to those not tested (25.5% vs 29.9%, p&lt;0.001). Of the 2387 eligible patients with RS &lt; 18, 117 (5.5%) received chemotherapy, which ranged from 0% - 13.6% across the 25 sites. Of the 341 patients with RS &gt; 30, 56 (9.8%) did not receive treatment with chemotherapy, which ranged from 0% - 50% across the sites. Of the 1192 patients with RS 18-30, 502 (45.7%) received chemotherapy, ranging from 14.5% for RS 18 to 72.5% for RS 30.

Conclusions: In sites across Michigan the majority of patients whose tumors were tested with the RS assay were in accordance with the NCCN guidelines, although there was considerable variability across sites. The rate of testing for patients who do not meet the NCCN criteria is increasing. There is very low inappropriate use of the recurrence score for making chemotherapy treatment decisions.

Citation Format: Ali HY, Munir K, Braun T, Griggs JJ, Silver SM, Gorski DH, Breslin TM, Henry NL. Appropriate use of the 21-gene recurrence score (RS) assay across Michigan. [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 P5-08-07.