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Updated: Feb 17, 2026
Optimization of a Multiplex RNA-based Expression Assay Using Breast Cancer Archival Material
Published on: August 1, 2018
Clinical Utility of Oncotype DX Testing in Synchronous Bilateral and Unilateral Multifocal Breast Cancer
Ho Hyun Ryu1, Young Jin Lee1, Tae Kyung Yoo1
1Division of Breast Surgery, Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Purpose:
We investigated the prevalence, clinicopathological correlates, and therapeutic implications of Oncotype DX recurrence score (RS) differences between synchronous tumors in bilateral and unilateral multifocal breast cancer.
Methods:
Patients with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative early-stage breast cancer who underwent Oncotype DX testing of at least two synchronous tumor foci at a tertiary center between 2015 and 2023 were retrospectively identified. Recurrence score risk-category discordance was defined according to cutoffs from the TAILORx and RxPONDER trials. Multivariable linear regression was used to identify the clinicopathological factors associated with absolute differences in RS. Disease-free survival was estimated by using the Kaplan-Meier method and compared using the log-rank test.
Results:
Among 131 patients (38 bilateral, 93 unilateral multifocal), RS risk-category discordance occurred in 21 and 24.7%, respectively, leading to chemotherapy escalation in half of the discordant cases. In bilateral disease, only the progesterone receptor score difference was significantly associated with the absolute RS difference (β = 1.95; 95% confidence interval [CI], 0.44-3.46; P = 0.013). In unilateral disease, absolute RS difference was independently associated with differences in HER2, progesterone receptor, and estrogen receptor scores (all P < 0.05). Recurrence score correlation between paired tumors was higher in unilateral multifocal than in bilateral disease (r = 0.66 vs. 0.36). Disease-free survival showed a consistent, although nonsignificant, trend toward poorer outcomes in discordant cases across both cohorts.
Conclusions:
Recurrence score risk-category discordance is frequent in synchronous bilateral and unilateral multifocal breast cancer and often changes adjuvant chemotherapy recommendations. Reliance on single-lesion testing risks missing clinically relevant genomic heterogeneity. Multilesion testing may be warranted in selected patients to optimize treatment selection.
