Abstract P4-02-10: Detection of H1047R and E545K PIK3CA mutations from peripheral blood in ER positive breast cancer patients

Abstract

Abstract Background: Digital polymerase chain reaction (PCR) is a new technology that enables detection and quantification of cancer DNA molecules from peripheral blood. Detecting tumor-specific mutations in circulating plasma DNA may potentially be useful to select systemic therapies for solid tumors. The aim of our study is to evaluate the feasibility of detecting PIK3CA mutations from plasma of breast cancer patients. Methods: We have designed an allele-specific PCR assay and used a digital PCR system for the detection of PIK3CA mutations H1047R and E545K. Formalin-fixed paraffin-embedded (FFPE) tumor samples were analyzed by COBAS and by digital PCR. The matched plasma samples were then analyzed by digital PCR. Kappa Cohen’s coefficient (κ) was used to test agreement between methods Results: 37 ER positive breast cancer and matched plasma were evaluated. 31 (84%) patients were stage IV disease. E545K mutation was detected in 4 out of 37 (11%) tumor specimens and H1047R mutation was identified in 8 out of 37 (22%) tumor samples. The proportion of observed agreement between H1047R and E545K detection in tumor samples by COBAS and digital PCR was 100%. Regarding E545K mutation assay we found that the proportion of observed agreement between mutation status in FFPE samples and circulating tumor DNA (ctDNA) was 94.6% (kappa= 0.770; Sensitivity=100%; Specificity=93.9%). In H1047R assay the proportion of observed agreement between FFPE samples and ctDNA was 83.78% (Kappa=0.561; Sensitivity=60%; Specificity=92.59%). Conclusions: The agreement between methodologies when assessing the PIK3CA status in tumor samples was perfect. However, a moderate-to-fair agreement was found between FFPE samples and ctDNA which might be due to the heterogeneity of the disease. The methodology presented in this study is a feasible approach for PIK3CA mutation detection in blood derived samples. Citation Format: Jose Angel Garcia-Saenz, Daniel Acosta, Fernando Moreno, Paticia Ayllon, Miguel Sotelo, Trinidad Caldes, Eduardo Diaz-Rubio, Atocha Romero. Detection of H1047R and E545K PIK3CA mutations from peripheral blood in ER positive breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-02-10.