Defining radiologic complete response using a correlation of presurgical ultrasound and mammographic localization findings with pathological complete response following neoadjuvant chemotherapy in breast cancer

Purpose: Breast cancer affects a significant number of patients younger than 40 years in the Gulf and breast conservative treatment is highly preferred. Pathological complete response (pCR) following neoadjuvant chemotherapy is increasingly being observed with the new chemotherapy agents. Although MRI is more accurate in such evaluations, digital mammography and high-resolution ultrasound (US) which are less expensive may accurately predict pCR which is the focus of this study. Methods: A 6-year retrospective study of 93 breast cancer cases who had neoadjuvant chemotherapy and had presurgical radiological localization was carried out. Forty-five had US localization while 48 underwent mammographic localization when US failed to define any residual mass. Radiologic complete response (rCR) was defined as absence of mass with only postbiopsy clip overlying normal breast parenchyma pattern in US and in mammography (clip sign). Mass or abnormal parenchymal pattern was considered as residual tumor. The pathology reports of pCR or not with background changes were recorded. Results: Ultrasound localization correctly predicted 42 out of 43 pathologic masses with 98 % accuracy. Mammographic localization correctly predicted 40 out of 43 pCR with 93 % accuracy. The best responders were triple negative and HER2 positive hormone negative breast cancer. Conclusion: The study defines radiologic complete response (rCR) as absence of a mass with the postbiopsy tissue marker overlying a normal-looking breast parenchyma in both ultrasound and mammographic evaluation. A correlation of 93 % was found with pCR. The few false negative cases were associated with overlying dense breast and possibly post treatment reaction. Allocation of a BI-RADS category for rCR is suggested.