Abstract PS5-37: The feasibility of obtaining oncotype DX breast recurrence score® results from metastatic sites of patients with hormone receptor positive metastatic breast cancer

Abstract

Abstract Background: Identifying when to start CDK4/6 inhibitors or use chemotherapy in hormone receptor positive (HR+) metastatic breast cancer (MBC) remains challenging. The 21-gene Oncotype DX Breast Recurrence Score® test is validated to predict chemotherapy benefit in early stage HR+ breast cancer but has not been studied for use in the MBC setting.Objective: To assess the feasibility of obtaining Recurrence Scores from metastatic sites after standard of care biopsy in HR+, HER2 negative patients and correlate Recurrence Score results from matched primary breast cancer when available. Methods: A total of 48 metastatic biopsies were retrieved retrospectively from the residual tissue of patients with primary HR+, HER2 negative breast cancer. This included 36 from bone and 12 from other sites [liver (7), lung (1), rectum (1), brain (1), skin (2)]. Slides were sent to Genomic Health Inc. for RNA isolation and Recurrence Score result determination using standardized protocols. Recurrence Score results were available for 18 matched primary and metastatic biopsy samples. The percent success rate for Recurrence Score result was determined for the various metastatic sites and results compared between matched primary and metastatic site. Results: Recurrence Score results were obtained in 48% of metastatic biopsies (23 of 48 samples) including bone (17), liver (4), lung (1), and skin (1). Reasons for Recurrence Score failure included insufficient RNA (17), poor quality RNA (1), failed QC (4), and other (3). The mean Recurrence Score from the 23 metastatic sites was 35 (range: 1–66). Notably, 70% (16/23) of successful metastatic biopsies yielded Recurrence Scores in the high-risk range (>25). None of the 23 metastatic biopsies gained HER2 by RT-PCR. Among the 18 paired samples, higher recurrence score results were observed in all but three of the metastatic biopsy samples with mean Recurrence Score results of 20 (range 7 to 41) for the primary and 35 (range 1-66) for the metastatic site. For paired samples, 72% of metastatic biopsies yielded Recurrence Scores >25 compared to 17% of primary sample. Primary Recurrence Scores were not predictive of metastatic scores (r2=0.052). Estrogen receptor (ER) expression status was conserved in 87% whereas progesterone receptor (PR) was lost in 69% of the metastatic lesion. Among the pairs, 5 had de novo metastatic disease. In these, the Recurrence Score was higher in the metastatic biopsy in each case compared to the matched primary (mean 36 versus 23, respectively). Among de novo cases, there was 100% concordance in ER positive and HER2 negative expression and only 60% concordance in PR expression between primary and metastatic sites. Conclusion: Using standard of care metastatic biopsy samples, a Recurrence Score result was successfully generated in 48% of samples including bone. This small series demonstrates wide variability in Recurrence Score results in metastatic disease with overall higher scores, common loss of PR, and minimal correlation to matched primary disease. Further examination of the potential significance of the Recurrence Score for treatment decisions in the metastatic setting requires additional tissue sampling during biopsy as insufficient RNA was the primary reason for failure. Citation Format: Julie Anne L Gemmill, Patricia Thompson, Rebecca Batiste, Caterina Vacchi-Suzzi, Christina Preece, Jules Cohen, Lea Baer, Carolyn Mies, Michelle Turner, Christy A Russell, Alison Stopeck. The feasibility of obtaining oncotype DX breast recurrence score® results from metastatic sites of patients with hormone receptor positive metastatic breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-37.