Currently, it is standard practice for the physician to do a breast examination to non-invasively assess whether the chemotherapy was effective, said Eren Yeh, MD, an instructor of radiology at Massachusetts General Hospital in Boston, and the lead author of the study. "Before we began the study, we weren't sure if breast tumors would enhance with the MR contrast agent gadolinium and therefore be visible after chemotherapy. Our study found that MRI is not perfect, but it's better than what's been used as the gold standard in the past," she said.
For the study, 31 patients prospectively underwent clinical examination, mammography, sonography and an MRI examination before, then following, chemotherapy. The results of these tests were then compared to the pathology results following surgery. MRI was right (when compared to pathology results) 71% of the time. It overestimated the amount of residual tumor in 6% and underestimated the amount of residual tumor in 23% of patients.
Sonography, on the other hand, was right only 35% of the time, overestimating the amount of tumor after chemotherapy in 13% and underestimating the amount of tumor in 52% of the cases. Clinical examination agreed with pathology in 19% of the cases, underestimating in 55% and overestimating the amount of disease in 26% of the cases; mammography was right in 26% of the cases, underestimating the amount of disease in 52% and overestimating in 23% of the cases.
In addition to being more accurate, MRI detected two additional lesions that were not seen on the other imaging methods, and these findings altered the way the patients were treated, said Dr. Yeh.
"In the future, we hope to use MRI earlier in the chemotherapy treatment to determine if the toxic therapy is reducing the tumor size. If it's not working, we can perhaps change the drug that's being used--in fact tailor treatment for each patient," she said.
The study appears in the March 2005 issue of the American Journal of Roentgenology.
A PDF of the full study is available upon request to reporters