Breast cancer: agreement between residual tumor size after neoadjuvant chemotherapy measurement with different imaging methods and the histological data

Background
The evaluation of residual tumor size post-neoadjuvant chemotherapy (NAC) could have an impact on surgical planning. Accurate measurement may avoid overly radical surgery or reduce the need for repeat surgery. The purpose of this study is to evaluate the size of residual tumor after NAC using mammography and ultrasound or MRI and thereby establish which imaging method shows most agreement with histological result.

Methods
Data from 125 patients, from 40 to 86 years old, with primary breast cancer and indication for neoadjuvant chemotherapy were analyzed in a retrospective study. All patients underwent conventional imaging (mammography and ultrasound) or MRI in addition to conventional imaging, after NAC and before surgery. Intra-class correlation (ICC) was calculated, and a Bland–Altman plot was used to determine the agreement between imaging residual tumor size (from US/mammography and MRI) and histological residual tumor size. The results were divided into the groups: invasive ductal carcinoma (IDC) + ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC) and “other tumors” (i.e., mucinous carcinoma).

Results
Of 125 analyzed patients, 44 (34.65%) underwent MRI and 81 (65.35%) had conventional imaging only. Agreement between residual tumor size founded on MRI and histological size is stronger than the data from conventional imaging.

Conclusions
MRI performance was generally superior to conventional imaging, and it may be considered the most appropriate test to evaluate the residual tumor size post-NAC before surgery.