Abstract 74P
Background
HER2DX genomic test is a valuable tool in clinical practice for patients (pts) with early-stage HER2+ breast cancer (BC). This study aims to share insights from the application of the test in a real-world setting, following its adoption in clinical use.
Methods
This is the first analysis of 214 HER2DX tests performed in consecutive pts with HER2+ BC. HER2DX were conducted at a central lab in Spain (2022-2023). We focused on evaluating the turn-around time, success rate, and outcomes of the test. Results were correlated with clinical-pathological parameters (tumor size, nodal status, estrogen receptor (ER), Ki67, and TILs). We utilized chi-square tests and Student’s t-tests.
Results
Cohort consisted of 214 pts (95% from Spain), median age of 56 years (range 32-90). ER+ were 71.1%, 59% had grade 2, 90% were invasive carcinoma NST and 5% lobular. Stage I, II, IIIA-B-C, IV disease represented 31.3%, 50.5%, 11.2%, 2.8%, 1.4% and 2.8%, respectively. Mean Ki67 was 35.8% and TILs were 16.0%. 74.8% were core needle biopsies. The success rate of tissue processing was 98.6%, and from there to generating a test report was 100%. Average turnaround time from receiving FFPE samples to reporting was 8.1 working days. Proportion of HER2DX high- and low-risk was 45.3% and 54.7%, respectively (varied according to clinical stage, except for stage II). Statistically significant differences in terms of grade and Ki67 was observed between HER2DX high- and low-risk, but not age, ER or TILs. In stage I, HER2DX high-risk according to a lower cutoff (i.e., 32) represented 26.9% of cases. Distribution across HER2DX pCR-high, -medium, and -low groups was 30.8%, 27.1%, and 42.1%, respectively. Significant differences in ER status, Ki67, TILs and grade were observed between HER2DX pCR-high and -low groups. Among the 10 lobular carcinomas, 90% were HER2DX pCR low/med, and 90% HER2DX low-risk. Finally, 15% of all tested cases had HER2DX ERBB2-low, and 88% (28/32) of them had HER2 2+.
Conclusions
Implementation of the HER2DX test is feasible and is being used across a wide range of clinical scenarios. The moderate alignment of HER2DX scores with standard clinical-pathological metrics, fitting expected patterns, provides new and meaningful insights for healthcare providers and pts.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.