Abstract 2407: Detection of hotspot PIK3CA mutations in primary tumors and plasma-cfDNA of breast cancer patients using a novel highly sensitive CE-IVD kit

Abstract Introduction: Detection of PIK3CA mutations in primary tumors (FFPEs) and liquid biopsy samples is of increasing importance for treatment decisions in breast cancer. Oncolipsy PIK3CA kit (Pharmassist Ltd, Greece) is based on the combination of allele-specific priming, asymmetric PCR, and melting curve analysis. The CE-IVD kit can detect the presence of four PIK3CA hotspot mutations (E542K, E545K, E545Q, H1047R). The aim of the present study was to: a) evaluate the performance of this novel CE-IVD kit both in FFPEs and plasma-cfDNA samples from patients with metastatic breast cancer (MBC) and b) directly compare the derived results using the Oncolipsy PIK3CA kit with the cobas® PIK3CA mutation test (CE-IVD, Roche Diagnostics, Germany) in identical gDNAs isolated from FFPEs samples. Patients and methods: We analyzed 42 primary tumors (FFPEs) and 29 plasma-cfDNA samples from patients with estrogen receptor (ER) positive metastatic breast cancer. Genomic DNA was isolated from FFPEs using the QIAamp DNA FFPE Tissue Kit (Qiagen, Hilden, Germany), while cfDNA was extracted from 2. 00 mL of plasma using the QIAamp DSP cNA Kit (Qiagen, Hilden, Germany). PIK3CA hotspot mutations were detected in the LightCycler® 2. 0 (IVD instrument, Roche Diagnostics, Germany) using the highly sensitive Oncolipsy PIK3CA kit (analytical sensitivity 0. 05%). A direct comparison study was performed using the cobas® PIK3CA Mutation Test on the cobas z 480 analyzer (IVD instrument, Roche Diagnostics, Germany). Results: In primary tumors the E545K mutation was detected in 22/42 (52. 4%), the E542K and H1047R mutations were detected in 11/42 (26. 2%) and 4/42 (9. 5%) of primary tumor samples, respectively, while the E545Q mutation was not detected in any FFPE sample tested. At least one PIK3CA mutation was detected in 14/29 (48. 3%) plasma-cfDNA samples. More specifically the E545K mutation was detected in 11/29 (38%), the H1047R mutation in 3/29 (10. 4%) and the E542K mutation in 2/29 (6. 9%) while the E545Q mutation was not detected in any plasma-cfDNA sample tested. In FFPEs, as expected, PIK3CA mutation frequency was higher compared to plasma-cfDNA. Direct comparison of the results derived using these two commercially available kits, the Oncolipsy CE-IVD kit and the cobas PIK3CA mutation test, using the same gDNA isolated from 42 FFPEs revealed a concordance of 34/42 (81%). Conclusions: The commercially available Oncolipsy PIK3CA CE-IVD kit is highly sensitive and specific for the detection of four PIK3CA hotspot mutations in primary tumors and plasma-cfDNA. Acknowledgement: This study has been financially supported by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH - CREATE - INNOVATE (project code: T1RCI-02935). Citation Format: Stavroula Smilkou, Dimitra Stergiopoulou, Eleni Tzanikou, Loukas Kaklamanis, Ioanna Balgkouranidou, Helena Linardou, Flora Zagouri, Evangelia Razi, Stylianos Kakolyris, Amanda Psyrri, Christos Papadimitriou, Ioanna Koukli, Athina Markou, Evi Lianidou. Detection of hotspot PIK3CA mutations in primary tumors and plasma-cfDNA of breast cancer patients using a novel highly sensitive CE-IVD kit abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2407.