Accurately assessing residual breast cancer after neoadjuvant chemotherapy minimizes morbidity and maximizes the cost-effectiveness of surgery. As chemotherapy can reduce tumor size, it has the added benefit of allowing for breast-conserving surgery. A multidisciplinary team from California looked at the role of MRI for pinpointing residual breast cancer in patients post-chemotherapy.
"We are currently developing new methods for characterizing change in tumor volume using MR imaging...however, accurate measurement of residual disease is a prerequisite to the accurate assessment of volumetric changes," wrote Dr. Savannah Partridge from the Magnetic Resonance Science Center at the University of California, San Francisco. Partridge’s co-authors were from the UCSF department of surgery and the department of pathology at Marin General Hospital in Greenbrae, CA (American Journal of Roentgenology, November 2002, Vol. 179:5, pp. 1193-1199).
For this study, 52 women with invasive breast cancer had MR exams before and after neoadjuvant chemotherapy. All patients underwent four cycles of doxorubicin and cyclophosphamide; nine patients also had 12 cycles of paclitaxel treatment.
MRI was performed on a 1.5-tesla Signa scanner with a bilateral phased-array open breast coil (GE Medical Systems, Waukesha, WI). Gadopentetate dimeglumine (Magnevist, Schering, Berlin, Germany) was administered at a dose of 0.1 mmol/kg of body weight.
"Because enhancing lesions become isointense to the bright fat signal on T1-weighted images, fat suppression was important for improving the conspicuity of abnormal tissue," the authors explained.
Initial tumor extent was identified on the pre-treatment MR images. The results of the MRI exam, the clinical exam, and pathology were used to assess breast tumors in these 52 women. After neoadjuvant chemotherapy, eight women had a complete pathologic response (no residual disease) and 44 residual tumors were measured with pathology.
"In the analysis of all patients, the correlation between post-treatment MR imaging size and pathology was high, with a 95% confidence interval (CI) of 0.82-0.93," the study stated. "The mean size of residual tumor found at pathology was 3.66 cm. All three complete responses that were determined on MRI also showed no residual disease at pathology."
There were five patients who had pathologic measurements deemed "problematic" for MRI comparison. In two cases, residual disease was present across the whole breast, and the pathologic size was larger than the entire breast diameter shown on MR. Two patients had ductal carcinoma in situ (DCIS) and invasive cancer based on pathology, but these abnormalities were not distinguishable on the MR exam.
One patient had measurable enhancement on MR, but no residual disease was found at lumpectomy. Thirty-nine weeks after surgery, the patient presented with a large local recurrence. The authors surmised that the area of enhancement had not been removed at lumpectomy.
Before treatment, the median tumor peak percentage of enhancement was 210%, decreasing to 166% after chemotherapy. The median value for the peak signal enhancement ratio dropped from 1.96 before treatment to 1.52 after treatment, which indicates lower rates of contrast washout in the treated tumors, the group said.
While previous researchers that have used MRI for post-chemotherapy evaluation have reported poor sensitivity, Partridge’s group pointed out that low image resolution may have been the problem.
For the UCSF study, a higher imaging resolution (0.703 x 0.94 x 2 mm) was used with fat suppression. In addition, the authors "chose to reduce our criterion for identifying carcinoma in the breast after treatment to any notable enhancement in the region of the prior tumor." This approach increased the sensitivity for the detection of carcinoma after chemotherapy.
Several papers in the breast MRI session December 4 at the 2002 RSNA meeting will focus on the modality’s role in post-treatment cases. A group from Italy will share its work on MR mammography for the evaluation of recurrent breast carcinoma after conservative surgery and radiotherapy (paper 1240). Also, Dr. Katya Siegmann from Tuebingen, Germany will discuss whether biopsy should be performed on suspicious breast lesions found exclusively with MR (paper 1242).
By Shalmali PalAuntMinnie.com staff writer
November 14, 2002
Related Reading
Contrast MRI improves cancerous lymph node detection, misses some primary tumors, October 31, 2002
Scintimammography catches chemoresistance in breast cancer patients, June 13, 2002
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