MR contrast patterns predict breast cancer therapy response

The permeability of gadolinium and the morphology of breast cancers can reliably predict whether those tumors will benefit from neoadjuvant chemotherapy, according to research presented at the San Antonio Breast Cancer Symposium in December.

Oana Craciunescu, Ph.D., a radiation oncologist at Duke University Medical Center, and colleagues injected gadolinium-DTPA into the locally advanced breast cancer of 20 women. A T1-weighted 3D fast gradient-echo technique was used over 30 minutes following bolus injection.

The researchers generated perfusion/permeability maps, which they used to morphologically characterize lesions as centripetal (inhomogeneous ring enhancement) or centrifugal (more uniform enhancement starting from center to periphery).

They also devised a scoring system (from 0 to 5) to account for the enhancement type, and for the washin and washout rates of the contrast material. These two scores were added and correlated with response to chemotherapy as determined by both pathologic residual tumor and MR imaging.

The pretreatment washout for all 20 patients peaked in the first one to four minutes after injection. However, the washin and washout parameters varied significantly for different tumors: In relative units, washin varied from 52 to 266, and washout from 0.6 to 8.5.

Scores for eight of nine nonresponders ranged from 0 to 1, while nine of 11 responders were in the 2 to 5 range. The specificity and sensitivity of this MRI-based scoring system were 89% and 90.9%, respectively, for predicting response to chemotherapy.

The three primary factors in predicting a tumor's response to chemotherapy were perfusion, permeability, and morphology/cellularity, or the number and placement of cancer cells in the tumor.

Just as tumors use vascularization to carry blood, they also use it to carry the contrast material, which indicates a likely positive response to therapy. Tumors that were closely packed with cancer cells, however, did not effectively retain the tracer, and these were consequently resistant to treatment.

Tumors in which the blood vessels formed a ring pattern around the center were also resistant to chemotherapy. Collapsed blood vessels in the center would not carry the drug there, Craciunescu said.

The best responders were homogeneous tumors in which blood vessels were evenly distributed throughout the tumor. In these tumors, the gadolinium tended to wash into and out of the tumor slowly.

For more information from the Diagnostic Imaging archives:

MR diffusion maps track response to tumor therapy

MR software differentiates cancer from benign lesions

Breast imagers focus on fine-tuning MR specificity

Breast imagers explore energy other than x-ray