Recurrence Score(®) Result Impacts Treatment Decisions in Hormone Receptor-Positive, HER2-Negative Patients with Early Breast Cancer in a Real-World Setting—Results of the IRMA Trial

SIMPLE SUMMARY: Hormone receptor-positive (HR+), HER2-negative (HER2−) is the most common breast cancer subtype (approximately 75% of all breast cancer cases). Adjuvant chemotherapy can be administered to patients that undergo operative tumor removal with only few metastatic axillary lymph nodes (0–3). However, using classical risk biomarkers to guide adjuvant chemotherapy recommendation leads to overtreatment of patients including unnecessary possible chemotherapy-related toxicities. This prospective study assessed whether the multigene-expression assay Oncotype DX(®) that has been validated in two large clinical phase III trials, effectively reduces adjuvant chemotherapy recommendation in a real-world setting. This study could demonstrate that absolute adjuvant chemotherapy recommendation can be reduced by nearly 15% using Oncotype DX(®). Furthermore, this study could show that the Oncotype DX(®) recurrence score correlates to classic biomarkers that are commonly used to classify the aggressiveness of breast cancer. ABSTRACT: Background: Patients with hormone receptor-positive (HR+), HER2-negative (HER2−) early breast cancer (eBC) with a high risk of relapse often undergo adjuvant chemotherapy. However, only a few patients will gain benefit from chemotherapy. Since classical tumor characteristics (grade, tumor size, lymph node involvement, and Ki67) are of limited value to predict chemotherapy efficacy, multigene expression assays such as the Oncotype DX(®) test were developed to reduce over- and undertreatment. The IRMA trial analyzed the impact of Recurrence Score(®) (RS) assessment on adjuvant treatment recommendations. Materials and methods: The RS result was assessed in patients with HR+/HER2− unilateral eBC with 0–3 pathologic lymph nodes who underwent primary surgical treatment at the Department for Women’s Health of Tuebingen University, Germany. Therapy recommendations without knowledge of the RS result were compared to therapy recommendations with awareness of the RS result. Results: In total, 245 patients underwent RS assessment. Without knowledge of the RS result, 92/245 patients (37.6%) would have been advised to receive chemotherapy. After RS assessment, 56/245 patients (22.9%) were advised to undergo chemotherapy. Chemotherapy was waived in 47/92 patients (51.1%) that were initially recommended to receive it. Chemotherapy was added in 11/153 patients (7.2%) that were recommended to not receive it initially. Summary: Using the RS result to guide adjuvant treatment decisions in HR+/HER2− breast cancer led to a substantial reduction of chemotherapy. In view of the results achieved in prospective studies, the RS result is among other risk-factors suitable for the individualization of adjuvant systemic therapy.