There was no statistically significant difference in ERRB2 (HER2) total gene copy number (pCR:19 and RD:29 median total copies; P = 0.79) and ERBB2 (HER2) cancer cell fraction (pCR: 0.33 and RD: 0.37 median CCF; P = 0.26) when comparing pCR (n = 9) to RD (n = 13) groups (Fig. 3a; Wilcox Test, P > 0.05; Supplementary Table 5). This evidence concerns the gene ERBB2 and cancer.