Abstract PS5-02-06: Is genetic testing of Her2-negative metastatic breast cancer patients implemented into clinical practice?

Abstract Background Timely genetic testing in HER2-negative metastatic breast cancer (mBC) patients is important to identify BRCA mutations and allow optimal treatment options including Poly(ADP-ribose)polymerase inhibitors (PARPi) and platinum salts. Yet, testing rates have been reported unsatisfactory. Evaluation of the implementation of genetic testing in a real-world setting is important to reveal and subsequently target potential inadequacies and risk factors that are associated with a low testing rate. Methods We performed a retrospective analysis including all HER2- mBC patients treated at the Department of Obstetrics and Gynecology of the Medical University of Vienna, Austria, starting from 10.4.2019 (date of EMA approval of Olaparib for gBRCAmut HER2- mBC). The primary objective of the study was to evaluate the rate of HR+/HER2- mBC patients treated at a single academic center in Austria that were recommended to undergo genetic testing by the treating physicians. The secondary objective of the study was to identify factors that were associated with a higher likelihood of having undergone genetic testing. We performed descriptive statistics as well as logistic regression analysis using R version 4.3.2. Results 47.6% (109 of 229) of HER2- mBC patients and therefore with an indication for genetic testing had been recommended to undergo genetic testing by the treating physicians. Of these informed patients, 89.0% (97 of 109) underwent genetic testing, of which 11.6% (11 of 95) had a BRCA mutation and were eligible for targeted treatment. In multivariate analysis younger age (p-value: 0.0007), HR+/HER2- subtype (p-value: 0.0000) and positive family history for breast and ovarian cancer (p-value: 0.0001) were significantly associated with the conduct of genetic counseling. Conclusion The present study showed low genetic counseling rates of HER2- mBC patients in a real-world academic setting especially in patients without specific risk factors for hereditary breast cancer. Informed patients showed a high willingness to undergo genetic testing. Genetic testing revealed targetable mutations in over 10% of tested patients and allowed additional treatment options. Citation Format: G. Pfeiler, F. Heinzl, C. Leser, D. Gschwantler-Kaulich, C. Singer, S. Kostic, A. Golescu, C. Deutschmann. Is genetic testing of Her2-negative metastatic breast cancer patients implemented into clinical practice? abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-02-06.