ERBB2 and cancer: Up to 25 ng of the ctDNA were sequenced with our error-corrected ctDNA-Seq panel (40 cancer genes, 221kb target region), which includes commonly mutated CRC driver genes (APC, TP53, FBXW7, PIK3CA, and SMAD2/4) and known EGFR-Ab resistance driver genes (KRAS, NRAS, EGFR, BRAF, MAP2K1, MET, NF1, FGFR2, and ERBB2) [1,2,3,4,5,6,7,8,9,10].