Oncotype DX™ Recurrence Score (RS) in Very Small Tumors: Does RS Influence Clinical Outcome?

Area of Science:

• Oncology
• Genomics
• Breast Cancer Research

Background:

• Tumor size is a known risk factor for breast cancer recurrence.
• The 21-gene expression assay (Oncotype DX™) provides a Recurrence Score (RS) that correlates with recurrence risk.
• Small tumors (≤1 cm) are generally associated with lower recurrence rates.

Purpose of the Study:

• To evaluate the impact of a high Recurrence Score (RS ≥26) on locoregional recurrence (LRR) and invasive recurrence (IR) in patients with small breast tumors (≤1 cm).
• To compare recurrence risks between small tumors with high RS (≥26) and small tumors with low RS (<26).

Main Methods:

• Retrospective analysis of 231 patients with breast cancers ≤1 cm and high RS (≥26) between 2008-2020.
• Comparison with a control group of 1,747 patients with breast cancers ≤1 cm and low RS (<26).
• Kaplan-Meier method for estimating LRR and invasive-recurrence free intervals; multivariable Cox regression for association analysis.

Main Results:

• Patients with high RS (≥26) demonstrated significantly worse time to LRR and invasive recurrence compared to those with low RS (<26) (p<0.001 for both).
• At 10 years, LRR-free probability was 88% for high RS vs. 96% for low RS; invasive recurrence-free probability was 87% vs. 95%, respectively.
• Recurrence Score was independently associated with LRR and IR in multivariable analyses.

Conclusions:

• Patients with small tumors (≤1 cm) and high RS (≥26) face a higher risk of LRR than those with small tumors and low RS, even with standard care.
• These findings support personalized treatment strategies for small tumors, potentially influencing decisions regarding radiotherapy omission or modality selection.