Liquid Biopsy Results for Cancer Mutations May Differ – Study Compares Idylla platform vs to OncoBEAM RAS CRC assay Interview with:

Dr. Ana Vivancos, Principal Investigator Cancer Genomics Group Vall d'Hebron Institute of Oncology (VHIO Barcelona 

Dr. Ana Vivancos

Dr. Ana Vivancos PhD, Principal Investigator
Cancer Genomics Group
Vall d’Hebron Institute of Oncology (VHIO
Barcelona What is the background for this study? What are the main findings?

Response: Our study was designed to address a key issue in liquid biopsy testing: analytical sensitivity. We know that mutations in plasma of mCRC patients show a wide range in their allelic frequencies (0.01-90%), the biological basis for which remains unclear. We also know that around 35% of cases show very low mutant allele fractions (MAFs), < 1%, therefore highlighting the need of using high sensitivity techniques in the routine lab in order to properly detect mutations.

We have compared two different testing methods that are being used in liquid biopsy:

Digital PCR (OncoBEAM RAS test, BEAMing) with a limit of detection of 0.02% vs qPCR (Idylla ctKRAS test, Biocartis) with an analytical sensitivity of 1%.

Our findings indicate that detection sensitivity decreases for the qPCR based method in cases with low MAF (<1%) and more so when MAF values are very low (<0.01%). What should readers take away from your report? 

Response: The importance of analytical sensitivity of the testing methods used in the lab to perform mutation testing in plasma. What recommendations do you have for future research as a result of this work?

Response: The study was performed on a cohort that had been previously identified as RAS mutant by OncoBEAM, which may bias results towards Digital PCR. To solve this, testing in tissue was also performed, and concordance rates between tissue vs plasma calculated. Results were aligned: Digital PCR showed higher concordance with tissue than qPCR for the <1% plasma MAF patients. 

Citations: Abstract presented at ASCO GI 2018 meeting

Saturday, January 20 Level 1 – West Hall 066, 7:00am-7:55am and 12:30pm-2:00pm, BOARD B19 (Abstract 592) poster session C (Cancers of the Colon, Rectum, and Anus), Evaluation of the sensitivity of RAS mutation detection of the Idylla platform in comparison to the OncoBEAM RAS CRC assay.  A. Vivancos, E. Aranda, M. Benavides, E. Elez, A. Gomez, M. Toledano, M. Alvarez, M. C. Parrado, V. García-Barberán, E. Diaz-Rubio.

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