Tuesday, 7 October 2008
The Fall meeting of ACRIN was held last week at Pentagon City in DC.
Of note was the report from UCSF-led ACRIN study, on the use of breast MRI in the assessment of neoadjuvant chemotherapy -
"MRI is superior to mammography for evaluating the response to neoadjuvant chemotherapy for breast cancer, according to the early results of a trial from the University of California, San Francisco (UCSF) and nine other academic centers in the U.S. The results were presented at last week's American College of Radiology Imaging Network (ACRIN) fall meeting".
The study was developed under ACRIN's protocol 6657, representing the imaging side of the larger I-SPY (Investigation of Serial Studies to Predict Your Therapeutic Response With Imaging and Molecular Analysis) trial aimed at gauging breast cancer treatment response. Sponsored by the Cancer and Leukemia Group B Foundation (CALGB), the I-SPY trial is "testing imaging and tissue-based biomarkers in combination, predicting neoadjuvant response to standard chemotherapy," explained Nola Hylton, Ph.D., a principal investigator from UCSF who discussed the results.
Participants were scanned four times during chemotherapy, including once pretherapeutically, once after the first cycle of chemotherapy, and a third time between the anthracycline and Taxol agents. A fourth scan prior to surgery was intended to detect residual disease and evaluate the post-treatment sensitivity and specificity of MRI. Mammography scans were acquired to coincide with the first and last MRI scans
MRI measurements included morpholgic measurements of the tumors classified according to BI-RADS criteria for breast MRI, including tumor diameter measurements. "We're also measuring by computer the volume of the tumor and the microvascular parameters of the tumor, PE [percent enhancement] and SER [signal enhancement ratio]," used to distinguish malignant tissue, said Hylton.
he investigational software assesses tumor volume quantitatively based on functional rather than anatomic criteria, she explained. "We are measuring something that is based on how these tumors enhance, and assigning [volume] based on an algorithm calling it part of the tumor or not. So it's really a virtual volume [that defines] areas of the image based on function, in this case how the tumors enhance."
The investigators acquired one T1-weighted precontrast and two T2-weighted postcontrast scans, "and from that we looked at the early ratio of enhancement from the early time point to the late time point," she said. This calculation yields the signal enhancement ratio, which distinguishes tumor from nontumor. Another protocol ensures that the direction of diameter measurements remains constant over the course of multiple imaging exams
At the end of surgery, 43% of the patients were complete responders, 38% were partial responders, and 10% demonstrated stable disease. "There were a larger portion of complete responders among those who also received Taxol," she said. "And there were a total of 82 pathologic complete responders, meaning that there was no invasive disease left at pathology. Sixty percent of patients had a complete solid lesion, and 32% had two identifiable lesions in the breast.
Compliance with the study was surprisingly good, especially considering the complexity of the protocol, requiring both biopsy and multiple imaging exams in addition to treatment, she said. In addition, lesion morphology was very similar to a pilot study. There were 36 single masses; 65 multilobulated masses with well-defined margins; 66 lesions with area enhancement, irregular margins, and nodularity; 30 of the same without nodularity; and 19 patients with septal spread.
Once the analysis has been completed, more precise data will be presented at the 2008 RSNA meeting in Chicago.