Clinical Utility of Genomic Recurrence Risk Stratification in Early, Hormone-Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer: Real-World Experience.

BACKGROUND RNA-based genomic risk assessment estimates chemotherapy benefit in patients with hormone-receptor positive (HR+)/Human Epidermal Growth Factor 2-negative (ERBB2-) breast cancer (BC). It is virtually used in all patients with early HR+/ERBB2- BC regardless of clinical recurrence risk. PATIENTS AND METHODS We conducted a retrospective chart review of adult patients with early-stage (T1-3; N0; M0) HR+/ERBB2- BC who underwent genomic testing using the Oncotype DX (Exact Sciences) 21-genes assay. Clinicopathologic features were collected to assess the clinical recurrence risk, in terms of clinical risk score (CRS) and using a composite risk score of distant recurrence Regan Risk Score (RRS). CRS and RRS were compared to the genomic risk of recurrence (GRS). RESULTS Between January 2015 and December 2020, 517 patients with early-stage disease underwent genomic testing, and clinical data was available for 501 of them. There was statistically significant concordance between the 3 prognostication methods (P < 0.01). Within patients with low CRS (n = 349), 9.17% had a high GRS, compared to 8.93% in patients with low RRS (n = 280). In patients with grade 1 histology (n = 130), 3.85% had a high GRS and 68.46% had tumors > 1 cm, of whom only 4.49% had a high GRS. Tumor size > 1cm did not associate with a high GRS. CONCLUSION Genomic testing for patients with grade 1 tumors may be safely omitted, irrespective of size. Our finds call for a better understanding of the need for routine genomic testing in patients with low grade/low clinical risk of recurrence.