Dynamic breast MRI helps assess axillary nodes

Dynamic contrast-enhanced MRI may be an alternative to invasive exploratory surgery for assessing lymph node status and determining if breast cancer patients require radiation treatment.

A study from the Seattle Cancer Care Alliance and the University of Washington Medical Center found that certain kinetic parameters of breast cancer tumors can determine the presence and absence of cancer progressing to the axillary nodes.

Dr. Christopher Loiselle, a radiation oncology resident at the UW Medical Center, reviewed MR studies of 167 patients who had been treated with radiotherapy for invasive breast cancer and had undergone surgical staging before receiving chemotherapy. Of these patients, 46 passed the inclusion/exclusion criteria, with 32 being found node negative and 14 node positive.

Peak enhancement during DCE-MRI was significantly higher in node-positive patients, with a mean uptake of 245% and a median uptake of 209%, compared with a 144% mean and a 138% median uptake in node-negative patients. Rapid enhancement was also significantly greater in node-positive patients, with a mean uptake of 48% and a median of 57% compared with a mean of 29% and median of 27% in node-negative patients. There was no difference in the wash-out percentages.

The percentages generally refer to the enhancement of the primary tumor compared with an initial non-contrast scan. Initial peak enhancement measured maximum single-voxel enhancement intensity in the primary lesion. Rapid enhancement considered the percentage of voxels in the primary tumor that showed at least a doubling of enhancement after gadolinium contrast administration. Wash-out was defined as the percentage of voxels in the primary tumor that lost more than 10% of their contrast intensity in a delayed scan. Sensitivity and specificity were not disclosed.

The results, presented at the 2008 American Society for Therapeutic Radiology and Oncology meeting, indicate that DCE-MRI kinetics can be used to evaluate the axillary node status. Over the last two decades, several randomized trials looking at women who have undergone mastectomy have shown that patients who are node positive are statistically most likely to benefit from radiation therapy, Loiselle said. Ultimately, the use of DCE-MRI may spare some women from radiation therapy, especially those with smaller tumors and tumors that have not spread to the lymph nodes.

In the yet-to-be published study, Loiselle and radiologist Dr. Peter Eby set out to determine if the kinetics of breast tumors on DCE-MRI correlated with axillary node status before the patient was treated with chemotherapy. Many breast cancer patients receive chemotherapy before surgery, exposing the axillary area to systemic treatment. That can make it difficult to know if there was cancer in the underarm lymph nodes.

Lead author Loiselle said the next step will be to evaluate the use of DCE-MRI as a prognostic tool for the recurrence of cancer in patients who did receive chemotherapy first.

"Determining which patients need chemotherapy and radiation therapy is one of the big picture challenges," Loiselle said.

-By Don Rauf