MYC and breast carcinoma: In conclusion, Shannon index for c-MYC CNV decreased after neoadjuvant chemotherapy especially in the chemo-sensitive group, and a post-treatment high Shannon index was found to be an independent poor prognostic indicator, suggesting that the change in Shannon index after neoadjuvant chemotherapy reflects chemo-responsiveness and that Shannon index after neoadjuvant chemotherapy can be used as a prognostic factor in patients with breast cancer who receive neoadjuvant chemotherapy.