Does the 21-gene recurrence score have clinical utility in HR+/HER2+ breast cancer?

The 21-gene recurrence score assay has been validated as a predictive biomarker in early-stage HR+ and HER2-breast cancer. It is not indicated for use in HER2+ disease based on national guidelines. In this study, we assessed the value of 21-gene recurrence score (RS), or OncotypeDX (ODX), testing in HR+/HER2+ breast cancer. We used the National Cancer Database to identify patients with stages I-II, HR+/HER2+ breast cancer who received multi-gene testing with ODX. We then explored the prognostic and predictive value of this biomarker through various forms of survival modeling. ODX testing was performed in n = 5,280 patients. N = 2,678 patients (50.7%) had a RS < 26, while n = 2,602 (49.3%) had a RS ≥26. In Kaplan-Meier survival modeling for patients with recurrence scores <26, there was no significant difference in overall survival (p = 0.445) between patients receiving different systemic treatment regimens. However, when recurrence scores were ≥26, there was a statistically-significant difference in overall survival between systemic treatment regimens (p < 0.001). 5-year overall survival was highest (97.4%) for patients receiving triple therapy (anti-HER2 with chemotherapy and endocrine therapy), followed by those receiving dual therapy with endocrine and anti-HER2 (96.7%), and endocrine with chemotherapy (94.9%). Patients receiving endocrine therapy alone exhibited the lowest 5-year overall survival (88.5%). RESULTS: Analysis from this large national cancer registry suggests that multigene testing may have predictive value in treatment selection for patients with early-stage, HR+/HER2+ breast cancer. Prospective trials are warranted to identify subgroups of patients with HR+/HER2+ breast cancer who can be spared anti-HER2 treatments and cytotoxic chemotherapy.