A preliminary single institution experience with droplet digital polymerase chain reaction (dd-PCR) liquid biopsy (LB) for therapeutic decision in advanced solid tumors: Personal precision oncology clinic and genetic diagnostics, Brazil.

Abstract

e14613 Background: Droplet digital polymerase chain reaction (dd-PCR) is a promising method for analyzing minor amounts of cell-free circulating free nucleic acid (DNA and RNA) due to its high sensitivity, low cost, and fast reading, since it dispenses bioinformatics, making it an appropriate alternative to new generation sequencing (NGS) for the detection of biomarkers to guide molecularly targeted cancer therapy. The assay covers main actionable hotspot alterations across many actionable genes: EGFR(mutations), ALK (fusion, mutations), ROS1(fusion), BRAF(mutations), KRAS (mutations), NRAS(mutations), ERBB2(CNV), ESR1(mutations), KIT(CNV) and PDGFRA(CNV). Methods: We analyzed so far 38 patients with advanced NSCLC: 13(35%), breast: 9(24%), colorectal: 6(16%), pancreatic: 4(10%), ovary: 2(5%), salivary gland: 2(5%), melanoma 1(2.5%), and GIST: 1 (2.5%). ddPCR was performed using the QX200 system (BIO-RAD, Hercules). All samples were tested in duplicate. All assays were performed at Personal Precision Genetic Diagnostics. Belo Horizonte, MG. Brazil. Results: We detected meaningful genomic alterations in 7(18.5%) patients: 4(10.5%) KRAS G12V mutations (all in colorectal cancer), 1(2.6%) EGFR Del19 mutation, 1 EGFR L858R mutation(2.6%), both in NSCLC and 1(2.6%) ERBB2 amplification (in breast cancer). MAF (Mutant Allele Fraction) varied from 0.9% to 24%. In all cases the results were decisive for the indication or the change of a targeted therapy. Conclusions: Our preliminary results suggest that dd-PCR is a highly sensitive method and could be used for a routine laboratory detection of the important genomic variations to determine the targeted therapy in patients with varied advanced solid tumors.