The clinico-radiological factors, absence of suspicious calcifications on mammography (odds ratio (OR) 3.75; 95% confidence interval (95% CI) 1.72–8.17), treatment with dual HER2-blockade (OR 2.36; 95% CI 1.17–4.75) and a (near) complete response on MRI (OR 3.55; 95% CI 1.31–9.64) were associated with DCIS response in univariable analysis (Tables 3, 4), as were the histopathological factors absence of calcifications in DCIS on pre-NST biopsy (OR 3.19; 95% CI 1.34–7.60) and Ki-67 expression > 20% in DCIS (OR 2.74; 95% CI 1.09–6.89). This evidence concerns the gene MKI67 and ductal breast carcinoma in situ.