Abstract 3067: PIK3CA hotspot mutations are present at a relatively high frequency in CTCs of operable and metastatic breast cancer patients

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Introduction: Molecular characterization of CTC is crucial for the investigation of molecular targeted therapies. PIK3CA somatic mutations play a crucial role in response to molecular targeted therapies. We detected PIK3CA mutations at a high frequency in CTC after developing and validating an ultra-sensitive methodology, based on a combination of allele-specific, asymmetric rapid PCR and melting analysis. Patient and Methods: After optimizing and validating our assay in terms of sensitivity, specificity and robustness, we detected PIK3CA hotspot mutations in EpCAM positive CTCs from 57 metastatic and 118 early breast cancer patients, 26 healthy individuals and 76 corresponding primary tumors. Rapid Real-PCR and melting were performed in triplicate for all samples in the LightScanner32 (Idaho USA), in the presence of LC-Green Plus saturating dye. Results: The assay could detect 0.05% of mutated dsDNA in the presence of 99.95% wtDNA for both exons and was highly specific (0/26 healthy). We identified PIK3CA mutations in EpCAM positive CTC in 20/57(35.1%) metastatic and in 23/118(19.5%) operable breast cancer patients. In corresponding primary tumors, 45/76(59.2%) samples were positive. Patients with verified metastasis carrying PIK3CA mutations on CTC had significant shorter OS than those without. Conclusions: We report for the first time that PIK3CA hotspot mutations are present at a relatively high frequency in CTC both in metastatic and operable breast cancer. The presence of PIK3CA mutations in CTC is associated with worse survival in patients with verified metastasis. Evaluation of PIK3CA mutational status on CTCs is a strategy with potential clinical application. Citation Format: Athina N. Markou, Sofia Farkona, Christina Schiza, Antonia Eftathiou, Nikolaos Malamos, Vassilis Georgoulias, Evi Lianidou. PIK3CA hotspot mutations are present at a relatively high frequency in CTCs of operable and metastatic breast cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3067. doi:10.1158/1538-7445.AM2014-3067