Serial measurement of tumor volume with magnetic resonance imaging may represent a real advance in assessing response of breast cancer to chemotherapy as well as predict risk for recurrence, according to an article in the June issue of the American Journal of Roentgenology.

The current study, performed at the University of California-San Francisco, of 58 breast cancer patients found that the best way to predict a patient's recurrence-free survival is to review the initial MRI examination (before the patient has chemotherapy) and the final MR examination (after chemotherapy has been completed).

“Initial tumor volume was a strong predictor of recurrence-free survival. Of the women who had tumor volumes of 33 cm3 or less on the initial MR exam, 93% remained disease free after two years compared with 70% of the women with larger tumors. This speaks strongly for the value of early detection,” said Savannah C. Partridge, PhD, now an assistant professor of radiology at the University of Washington, Seattle.

“The change in tumor volume with treatment was also a valuable predictor,” said Partridge. “We found that the group of patients who had a 50% or greater reduction in MRI tumor volume when comparing the first MR examination to the last had a better recurrence-free survival rate (87% remained disease-free after two years) than those with less tumor shrinkage during chemotherapy treatment (64% were disease-free after two years), irrespective of their initial tumor volumes,” she added.

One patient with a large focal mass showed a substantial decrease in tumor volume on MRI during treatment and continues to be disease-free 40 months after surgery. In contrast, a second patient, with a more diffuse mass, showed an increase in tumor volume on MRI during treatment that was not detected by clinical examination. Her disease returned eight months after surgery, said Dr. Partridge.

Most often, MRI is used to measure the tumor’s diameter, said Dr. Partridge. “This study shows that while measuring tumor diameter is useful for staging, volume is preferable for monitoring treatment because three-dimensional volume measurements can more accurately capture the extent of irregularly shaped tumors, multifocality and diffuse shrinkage of lesions during treatment,” she said. “It is important that an accurate and validated tool be used for calculation of three-dimensional tumor volume from MRI images,” she noted.

Physicians now typically evaluate treatment response by clinical exam and pathology. “But unlike pathology, early changes in tumor volume can potentially be assessed by MRI at a time when chemotherapy regimens can still be modified. Our study showed that MRI measurements of breast tumor volume can help predict recurrence-free survival. We are encouraged by these results and anticipate that monitoring tumor response by MRI will help us to better tailor treatment strategies for individual patients. A larger multi-center study is currently underway to see if MRI can determine if chemotherapy is working early enough for treatment to be changed,” she said.