Recent pCR reports in 27% to 44% HER2-positive cancers after 12 to 16 weeks of combination therapy (30, 31) imply that there is a group of patients with HER2 whose primary cancers are highly dependent on HER2 signaling, and their early identification would (if validated in further studies) allow testing of the omission of chemotherapy without detrimental effects on oncologic outcomes. Here, ERBB2 is linked to cancer.