ERBB2 and breast cancer: Moreover, the NeoALTTO trial exanimated at the correlation between ctDNA and reaction to anti-HER2 treatment and found that HER-2-positive tumors without ctDNA at baseline showed better rates of pathologic complete response (pCR), suggesting that ctDNA may be exploited as a new biomarker for neo-adjuvant chemotherapy (NACT) reaction in HER-2-positive BC.