MR quantification of the washout changes in breast tumors under preoperative chemotherapy: Feasibility and preliminary results

OBJECTIVE. The objective of our study was to describe and determine the feasibility of an MR washout quantification method inpatients with breast cancer under preoperative chemotherapy. MATERIALS AND METHODS. Nineteen patients with breast T2 or T3 tumors were enrolled in a previous study for tumor response evaluation during chemotherapy based on dynamic contrast-enhanced MRI. We retrospectively used the dynamic acquisition data to produce parametric images representing the washout pattern. Two radiologists unaware of the final pathologic results measured the volume of pixels exhibiting washout within the tumor before chemotherapy (volume 1), after two courses of chemotherapy (volume 2), and before surgery after four courses of chemotherapy (volume 3). The interobserver variability and intraobserver variability were calculated to evaluate the reproducibility of our method with the Pearson's correlation coefficient and the concordance correlation coefficient. We correlated the washout changes by means of a Student's t test and noted the histopathologic final outcome. RESULTS. A washout pattern was present in all patients on the initial MR study. The quantification method of the washout changes was reproducible with good interobserver agreement (r = 0. 85, p < 10(-5)) and an excellent intraobserver agreement (r = 0.94, p < 10-5). A significant decrease of the washout volume was observed after two courses of chemotherapy (P = 0.004), whereas no significant modification was observed between two and four courses of chemotherapy (p = 0.52). CONCLUSION. Quantification of the washout variation in breast tumor based on the use of parametric images is feasible and reproducible. It may add information to the evaluation of tumor response to preoperative therapy.