We used NOIR-SS to target regions of eight pancreatic cancer-related genes: KRAS, TP53, SMAD4, CTNNB1, CDKN2A, GNAS, HRAS, and NRAS. The total size of the target regions was 2.8 kb. In the original version of NOIR-SS , barcode-tagged adapters were attached to the template DNA molecules after digestion with restriction enzymes. Since this procedure limited the choice of the target regions, here we attached the barcode-tagged adapters directly to the undigested ends of the cfDNA. As end positions of cfDNAs were variable, target sizes ranged from 110 to 260 bp, including adapter sequences. For library construction, we amplified target regions with approximately 4.5 ng of cell-free DNA using the adapter and a mixture of gene-specific primers after a linear amplification step with only the gene-specific primers. The reaction scheme is presented in Fig 1. The library was subjected to NGS on an Ion Torrent sequencer. Sequence reads were grouped using molecular barcodes. After removal of erroneous sequences, high quality sequence data were used to build a consensus sequence for each read group. The sequencing depth was at least 100 per molecule. The average number of sequenced molecules was 900 per target region.