8P First Decision Impact Study of HER2DX in Patients (pts) with HER2-positive (HER2+) Early Breast Cancer

HER2DX is a genomic test based on the expression of 27 genes tracking 4 signatures (luminal, proliferative, immune and HER2 amplicon) that provides prognostic (HER2DX risk score) and predictive information (HER2DX pathologic complete response [pCR] score) in HER2+ early breast cancer (BC). Here, we report the initial results of the first ongoing decision impact study of HER2DX at Hospital Clinic of Barcelona. We conducted an observational, prospective, pilot, unicentric study, since Nov/21 (ongoing), to analyze the impact of HER2DX in clinical practice in early-stage HER2+ BC. Any medical oncologist of the Breast Unit could order the test. A survey was completed by the treating physician before and after receiving the result of HER2DX. The main objective was to assess the % of change in the therapeutic plan after obtaining the HER2DX report. Secondary objectives included 1) assess changes in the physician’s confidence before and after the test and 2) analyze the association of the HER2DX pCR score with the pathological response after neoadjuvant therapy (NAT). Descriptive statistics were used. We report the results after the inclusion of the first 89 pts (as of 2nd of Feb/23). Median age was 53 years (range 30-79) and 52% of pts were postmenopausal. Most pts had T1-2 tumors (87%), negative nodes (64%), grade 2 (56%) or 3 (41%), ductal histology (87%), hormone receptor positive (65%), median Ki67 of 35% (range 4-90%) and median tumor-infiltrating lymphocytes of 10% (range 0-90%). 78% of pts received NAT and 22% upfront surgery. A change in the treatment plan before and after the HER2DX result was observed in 49 of 87 (56%) cases. De-escalation of therapy was observed in 59% of pts (less intense chemotherapy [ChT] in 57% of them) and escalation in 41% of pts (more intense ChT in 65% of them). The confidence in the decision improved in 67% of cases. Among 56 evaluable pts treated with NAT, HER2DX pCR score was significantly associated with pCR (81% in pCR-medium/high and 32% in pCR-low; odds ratio=9.3, p=0.001), independently of the rest of variables. In this first pilot and prospective study, HER2DX impacted clinical care in early-stage HER2+ BC.