Abstract P1-08-14: Trend of utilization of Oncotype DX testing among female hormone receptor positive breast cancer patients in 17 SEER registries, 2004-2015
Authors: Zhang L , Hsieh M-C , Petkov VI , Yu Q , Wu X-C 
Published: May 2019

Abstract
Background: Oncotype DX, a 21-gene Recurrence Score (RS) assay, has been validated as assay that effectively predicts recurrence and chemotherapy (chemo) benefits for hormone receptor positive (HR+) human epidermal growth factor receptor 2 negative (HER2-) breast cancer (BC). Although guidelines recommend the test to lymph node (LN) negative (PN0) BC patients, it has also been used in patients with 1-3 positive LN (PN1) in clinical practice. The study aimed to 1) examine the trend of utilization of Oncotype DX testing for HR+ and PN0 or PN1 BC patients from 2004 to 2015, as well as the trend in patients with different clinical risk; 2) investigate the trend of having reported chemo in patients with low, intermediate, and high RS; and 3) compare cause-specific survival (CSS) and overall survival (OS) between patients who had test and those who did not.
Methods: Data from Genomic Health Inc., the sole Oncotype DX testing provider in the U.S., was linked with routinely collected data from 17 SEER registries. Women who received surgery for stage I-III, HR+ and PN0 or PN1 BC diagnosed in 2004-2015 were included. The Cochrane-Armitage trend test was conducted for trend analysis. Using the overall sample as standard population (frequency of each age-racial group in overall sample as weight), age-race standardized percentage of test use was calculated. Since HER2 data was available only after 2010, survival analysis was restricted to HR+/HER2- patients diagnosed in 2010-2014 whose BC was the only primary tumor. Patients who used and those who did not use the test were matched on propensity score, which was calculated based on age, race, marital status, insurance, grade, tumor size, surgery type, radiation, and chemo within each diagnosis year. Stratified Cox proportional hazards model was used to compare survival between two matched groups. Proportional hazard assumption was met for each model.
Results: Out of 346,380 PN0 and 103,317 PN1 patients, the percentage of using Oncotype DX test increased from 2.0% to 38.2%, and from 0.5% to 28.0% from 2004 to 2015, respectively (P-for-trend &lt; 0.0001 for each). Age-race standardized percentage of test use was the highest and increased most rapidly for tumors with intermediate clinical risk (moderately differentiated or tumor size 2.1-5.0cm) among PN0 patients, but for tumors with low clinical risk (well differentiated or tumor size ≤2.0cm) among PN1 patients. From 2004 to 2015, the percentage of having reported chemo decreased in patients with low (PN0: 14.7% to 1.8%; PN1: 27.3% to 16.2%) and intermediate RS (PN0: 36.1% to 28.6%; PN1: 60.0% to 44.7%), but increased among patients with high RS (PN0: 59.0% to 75.4%; PN1: 66.7% to 74.2%). Test use was associated with better CSS (PN0: hazard ratio [HR] 2.15, 95% CI 1.73-2.67; PN1: HR 2.83, 95% CI 2.02-3.95) and OS (PN0: HR 2.05, 95% CI 1.81-2.33; PN1: HR 2.65, 95% CI 2.10-3.35).
Conclusions: The use of Oncotype DX test has increased steadily among female HR+ BC patients since 2004. It reduced unnecessary chemo among patients with low or intermediates RS, and increased chemo use in patients with high RS. Among HR+/HER2- patients, those who used test had better CSS and OS than those who did not.
Citation Format: Zhang L, Hsieh M-C, Petkov VI, Yu Q, Wu X-C. Trend of utilization of Oncotype DX testing among female hormone receptor positive breast cancer patients in 17 SEER registries, 2004-2015 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-14.