MRI of breast cancer: influence of chemotherapy on sensitivity

MR mammography (MRM) seems to be a sensitive method for detection of breast cancer. The effect of cytotoxic agents on the dynamics of contrast medium uptake in primary breast carcinoma or recurrent disease is not known. This study addresses this question and evaluates MRM as a method of monitoring therapeutic success. A total of 13 patients (age range 34-62 years) with histologically confirmed breast cancer were investigated. The patients received neoadjuvant intravenous (iv) chemotherapy. MRM and interpretation of the dynamic measurements were performed in a standardized manner after positioning the patient in a double breast coil. A gradient echo sequence (Flash 3D, TE 5 ms, TR 12 ms, flip angle 25 degrees) was acquired before and 1, 2, 3 and 8 min after intravenous injection of Gd-DTPA 0.15 mmol kg-1 body weight. A T2 weighted SE sequence (TE 103 ms, TR 6900 ms, 4 mm, field of view 350 mm) was also obtained. MRM was performed prior to histological evaluation and after chemotherapy. All cases of malignancy were correctly diagnosed with MRM. Based on MR findings, eight patients were classified as "responders" and the remaining as "non-responders". In the "responders" a flattening of the Gd-DTPA uptake curve after the first cycle of chemotherapy of complete absence of Gd-DTPA uptake after the fourth cycle was observed. The change in Gd-DTPA uptake behaviour led to an underestimation of the extent of tumour in two patients and false negative findings in four patients. MRM provides information regarding response to therapy following the first cycle. MRM does not provide information regarding invasive tumour tissue in "responders".