Abstract P3-10-04: Disparities in human epidermal growth factor receptor 2 testing completion: A population-based retrospective cohort study, 2010-2013
Authors: Schroeder MC , Neuner JM , Xia C , Thomas A 
Published: March 2017

Abstract
Introduction: Human epidermal growth factor receptor 2 (HER2) is an established biomarker predictive for response to HER2-targeted therapies. Testing breast cancer specimens for HER2 protein overexpression or gene amplification is the standard of care. Earlier work showed inconsistent delivery of HER2 testing to some patient groups. We sought to understand current imbalances in HER2 testing.
Methods: Our retrospective cohort analysis of Surveillance, Epidemiology and End Results Program data included women diagnosed with microscopically confirmed, first primary malignant breast cancer from 2010-2013. Women were categorized by race, stage, age, and whether they received HER2 testing. Those with unknown information in any of these variables were excluded. Descriptive analyses and multivariate logistic regression assessed the effect of these factors on the likelihood of not receiving HER2 testing.
Results: The full cohort included 182,032 women, of which 3,551 (2.0%) did not undergo testing for HER2 (Table 1). The portion of HER2 untested tumors was higher for African American women (2.3%) and other non-white women (2.2%), women over age 70 (2.3%) and women with Stage I (2.3%) or Stage IV disease (5.0%). Within the African American cohort similar patterns were seen: age &gt;70 (2.8%), Stage I (2.8%) and Stage IV (5.4%). The portion of women with untested tumors decreased from 2010 to 2013: 2.6% to 1.6% (p&lt;0.001) for the full cohort, and 2.9% to 1.9% (p&lt;0.001) for African Americans. On multivariate analysis, odds of not undergoing testing were highest for African American women (OR=1.27, p&lt;0.001), women of age &gt;70 (OR=1.26, p&lt;0.001), and women with Stage IV disease (OR=4.07, p&lt;0.001) (Table 2). Odds of not undergoing HER2 testing decreased over time (OR=0.60 for 2013 vs 2010, p&lt;0.001).
Conclusion: Persistent, and significant, disparities in completion of HER2 testing suggest that reasons for not testing extend beyond technical issues. While proportionally small, given the prevalence of breast cancer, addressing these disparities in HER2 testing may offer an opportunity to deliver life-prolonging, often well tolerated, therapy to significant numbers of patients. The improvements in delivery of HER2 testing seen over time are reassuring.
Table 1. Portion of women not having HER2 testing. Full Cohort African Americans N%p-valueN%p-valueN3,5512.0 4702.3 Race White2,7081.9&lt;0.001 African American4702.3 4702.3 Other3732.2 Age at diagnosis &lt;507081.7&lt;0.0011051.90.024 50-598921.9 1302.3 60-698941.9 1202.4 70+1,0572.3 1152.8 Stage I2,0692.3&lt;0.0012232.8&lt;0.001 II7621.3 1111.4 III2211.0 441.4 IV4495.0 925.4 Year of diagnosis 20101,0662.6&lt;0.0011322.9&lt;0.001 20119432.1 1442.8 20128011.7 931.7 20137411.6 1011.9
Table 2. Multivariate logistic regression for odds of not having HER2 testing. OR*p-valueRace Whiteref African American1.27&lt;0.001 Other1.24&lt;0.001Age at diagnosis &lt;50ref 50-591.080.128 60-691.010.795 70+1.26&lt;0.001Stage Iref II1.87&lt;0.001 III0.81&lt;0.001 IV4.07&lt;0.001Year of diagnosis 2010ref 20110.80&lt;0.001 20120.66&lt;0.001 20130.60&lt;0.001* Odds of group not being tested vs being tested, compared to the reference group and controlling for all other factors.
Citation Format: Schroeder MC, Neuner JM, Xia C, Thomas A. Disparities in human epidermal growth factor receptor 2 testing completion: A population-based retrospective cohort study, 2010-2013 [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 P3-10-04.