Abstract P2-08-15: 21-gene recurrence score testing utilization among older women from different races: A surveillance, epidemiology and end results (SEER) study
Authors: Gulbahce Evin , White Sandra , Stoddard Gregory J , Herget Kim , Sweeney Carol 
Published: March 2020

Abstract
Background: About 50% of breast cancers (BrCa) occur in women over the age of 65. Although chemotherapy improves survival in patients with estrogen receptor (ER) positive BrCa, benefits of chemotherapy in older woman must be weighed against the risks of morbidity associated with chemotherapy and non-BrCa associated mortality at older ages. OncotyeDX, 21-gene Recurrence Score (RS) identifies patients who may benefit from chemotherapy. In this study we looked at utilization of RS testing and likelihood of high-risk RS score in the older population across different races. Materials and Methods: We used Surveillance Epidemiology and End Result (SEER) data, linked to RS scores by the SEER program, to identify women older than 18 diagnosed with ER positive BrCa between the years 2004 and 2015. Patients with Stage 4 disease and T4 tumors were excluded. Patients were stratified into low (RS &lt;11), intermediate (RS 11-25), and high-risk (RS&gt;25) groups following TAILORx trial cut offs. Multivariable logistic regression model was used to identify factors associated with utilization of RS testing and association with high-risk RS. Results: Of 539,693 patients older than 18 years of age with ER positive, stage I-III BrCa identified between 2004 and 2015 in SEER registries, 109,835 (20.35%) had RS testing performed. The odds of having RS testing done was lower among women ≥65 compared to younger women in all races. The characteristics that increased odds of testing included progesterone receptor positive tumors, later years of diagnosis (2010-2015 compared to 2004-2009), negative nodes, T1 tumors, and Grade 1-2 (compared to Grade 3) tumors, were largely consistent across race groups. Blacks and American Indian/Alaskan Natives had higher odds of high-risk RS compared to non-Hispanic whites, after adjusting for stage, grade, and age. Being age 65 and older reduced the odds of having high-risk RS by odds ratio (OR) 0.58 in non-Hispanic whites, adjusted for progesterone receptor status, tumor size, positive nodes, and grade. The reduced odds of high-risk RS associated with being age 65 and older was more pronounced among black women, adjusted OR 0.44 (0.37 - 0.51) and among Asian or Pacific Islander women OR 0.44 (0.37 - 0.51). Conclusion: Older women of all races are less likely to be tested for 21-gene RS. Among women who were tested, those age 65 and older were less likely to have high-risk RS result. Blacks and American Indian/Alaskan Natives have higher risk of having high-risk RS after controlling for stage, age and other clinical and pathologic predictors.
Citation Format: Evin Gulbahce, Sandra White, Gregory J Stoddard, Kim Herget, Carol Sweeney. 21-gene recurrence score testing utilization among older women from different races: A surveillance, epidemiology and end results (SEER) study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-08-15.