RAS analysis of circulating tumor cells from advanced colorectal cancer using BEAMing technology.

person Santiago Cabezas-Camarero Hospital Clinico Universitadio San Carlos, Madrid, Spain info_outline Santiago Cabezas-Camarero, Vanesa García-Barberán, Virginia De la Orden-García, Beatriz Mediero-Valeros, Mateo Paz Cabezas, Ana López-Alfonso, Antonio Carlos Sánchez Ruiz, Ana Ruiz-Casado, Isabel Díaz-Millán, Javier Sastre, Miguel Sotelo Lezama, Eduardo Diaz-Rubio

Authors person Santiago Cabezas-Camarero Hospital Clinico Universitadio San Carlos, Madrid, Spain info_outline Santiago Cabezas-Camarero, Vanesa García-Barberán, Virginia De la Orden-García, Beatriz Mediero-Valeros, Mateo Paz Cabezas, Ana López-Alfonso, Antonio Carlos Sánchez Ruiz, Ana Ruiz-Casado, Isabel Díaz-Millán, Javier Sastre, Miguel Sotelo Lezama, Eduardo Diaz-Rubio Organizations Hospital Clinico Universitadio San Carlos, Madrid, Spain, Hospital Clínico San Carlos, Madrid, Spain, Hospital Clínico Universitario San Carlos, Madrid, Spain, Hospital Universitario Infanta Leonor, Madrid, Spain, Hospital Universitario Puerta de Hierro, Madrid, Spain, Hospital Clinico San Carlos, Madrid, Spain, Hospital Universitario Infanta Cristina, Madrid, Spain Abstract Disclosures Research Funding Other Background: RAS mutations predict a lack of response to anti-EGFR therapies in metastatic colorectal cancer (mCRC). BEAMing technology is useful for detecting hot-spot mutations in ctDNA in mCRC. Analysis of these mutations in DNA from Circulating Tumor Cells (CTC) may increase the predictive value in mCRC patients (pts). Our aim was to explore the feasibility of studying RAS status using BEAMing in DNA from CTC. Methods: First, spiking experiments (SE) using wild-type (WT) and KRAS-mutated (MUT) cell lines were performed to establish the limit of detection (LOD) for RAS analysis with BEAMing. Second, SE were performed with CTC collected by CellCelector (removes non-CTC background achieving 100% purity of CTC). Finally, BEAMing was used for RAS analysis in ctDNA and in DNA from CTC isolated either with IsoFlux or with CellCelector in 9 mCRC pts with confirmed RAS mutation in primary tumor. Total DNA from CTC was preamplified using RepliG. Results: In SE, 10 and 5 KRAS MUT-cells using different backgrounds of WT-cells (10-0.2% MUT-cells) were detected using BEAMing. However, 3 and 1 MUT-cells (0.009-0%) were not detected. In SE of CTCs collected with CellCelector, BEAMing detected KRAS mutations with 50, 20, 10, 6, 4, 2 and 1 cell (MAF: 23.8%±3.8). A mutation (codon 13) was detected in CTC from one patient positive in tissue and ctDNA (CellCelector; 15 CTCs; MAF: 11.4%). Discordant results were found in 8 patients when CTCs were isolated using Isoflux (min: 0, max: 9 CTCs). CTC from another patient were possibly mutated but WT in ctDNA. Conclusions: This pilot study indicates that RAS mutations can be detected in CTCs using BEAMing. Reducing the non-CTC cellular background may be needed in cases with low CTC number. Molecular information provided by CTC and ctDNA may prove complementary and useful for taking therapeutic decisions in mCRC. These results merit confirmation in larger, prospective studies.