ERBB2 and neoplasm: To get a first overview of the cohort, we estimated the mean values of the biomarkers (i.e., measurements from all tumor cells within a sample) and found patients with nonpathological complete response (non‐pCR) to have a significantly lower mean copy number of the HER2 gene compared to patients with pathological complete response (pCR) (Fig. S2A, t‐test: P = 0.02).