Background and purpose: Neoadjuvant chemotherapy to breast cancer has become a mature treatment method. The purpose of this study was to evaluate the dynamic contrast-enhanced MRI in assessing the response to neoadjuvant chemotherapy (NAC). Methods: Twenty-four female patients with breast carcinoma (24 were all invasive ductal carcinoma) underwent dynamic contrast-enhanced MRI (DCE-MRI) before

after the second and final cycle of NAC. For each patient and each MRI examination

the maximum diameter of tumor

volume transfer constant (K

trans

)

exchange rate constant (K

ep

)

and extravascular extracellular volume fractio

n (V

e

) were compared. According to the method of response evaluation criteria in solid tumor (RECIST)

the results of neoadjuvant chemotherapy were divided into responder and non-responder. Results: All 24 patients were unilateral and single breast cancer; there were 17 cases of responders and 7 cases of non-responders according to RECIST criteria. For 17 cases of responders

both the average values of K

trans

and K

ep

were significantly descended after neoadjuvant chemotherapy (all P0.05). Conclusion: The quantitative parameters of K

trans

and K

ep

can evaluate objectively and veridically the response to neoadjuvant chemotherapy for breast cancer in dynamic contrast-enhanced MRI.