ERBB2 and breast cancer: Clostridiales appears to be significant in the treatment of HER2 positive breast cancers, noting a greater abundance of Clostridiales and less Bacteroidales in the feces of patients who achieved pathological complete response with neoadjuvant trastuzumab.254 The proposed mechanism is that commensal gut bacteria may enhance the response to monoclonal antibody therapy via greater recruitment of immune cells to the TME.