Nanofluidic Digital PCR for KRAS Mutation Detection and Quantification in Gastrointestinal Cancer

cogene homolog) alleles may provide information in addition to that provided by standard mutation-detection procedures. We assessed the feasibility of a nanofluidic digital PCR array platform to detect and quantify KRAS mutations simultaneously in clinically relevant samples. METHODS: We assessed 2 groups of patients (colorectal and pancreatic disease): Group 1 consisted of 27 pa-tients with colorectal carcinomas, 14 patients with ad-enomas, and 5 control individuals; group 2 consisted of 42 patients with pancreatic carcinoma, 4 with adeno-carcinomas of the ampulla, and 6 with chronic pancre-atitis). Digital PCR was performed with the Digital Ar-ray Chip (Fluidigm). RESULTS: Nanofluidic digital PCR detected mutant al-leles at 0.05 % to 0.1%, depending on the variant ana-lyzed. For the colorectal disease group, conventional PCR detected 9 (64%) of 14 adenomas that were posi-tive for KRAS mutants, whereas digital PCR increased this number to 11 (79%) of 14. Sixteen (59%) of 27 carcinomas showedKRASmutation with conventional PCR. Two additional cases were detected with digital PCR. In 5 cases (3 adenomas, 2 carcinomas), the total number of mutant alleles changed. For the pancreatic disease group, digital PCR increased the number of positive cases from 26 to 34 (81%) and identified 2 mutant alleles in 25 cases, compared with conventional PCR, which identified multiple KRAS mutant alleles in only 12 cases. A good correlation was observed between results obtained with tumor biopsies and those ob-tained with pancreatic juice. CONCLUSIONS: Digital PCR provides a robust, quantita-tive measure of the proportion of KRAS mutant alleles in routinely obtained samples. It also allows a better classification of tumors, with potential clinical relevance