ERBB2 and breast cancer: In patients with initial HER2-negative breast cancer, adding a dendritic cell vaccine to neoadjuvant chemotherapy (preoperative chemotherapy) (NCT01431196) significantly increased the percentage of pathological complete response (pCR, or disappearance of the tumor after surgery) to 26.3% and reduced tumor stage (surgical downstaging) in 13% of patients (30).