Breast MRI assesses tumor size the best prior to surgery, post-treatment

MRI is the best method to assess breast cancer tumor size prior to surgery and after chemotherapy, according to findings from the American College of Radiology Imaging Network trial 6657. Size on mammography does not correlate with true residual disease in patients treated with neoadjuvant chemotherapy and thus MRI is the best modality, the researchers said.

Portions of the ACRIN trial were presented at previous meetings, but the current piece, presented at the 2009 RSNA meeting on Tuesday afternoon, focuses specifically on using MRI post-treatment and presurgery.

The researchers measured residual disease in 216 patients through clinical exam, MRI, and mammogram. Pathologic residual disease size was most highly correlated with longest diameter measured by MRI across all lesions, according to the presenter of the study Dr. Constance Lehman, director of breast imaging at the Seattle Cancer Care Alliance in Washington.

The longest diameter measured by MRI was also the strongest predictor for single regional enhancement extent of disease surgery, she said.

After MRI longest diameter, pathologic residual disease size was most highly correlated with MRI volume and then clinical exam. Pathological residual disease size was not significantly correlated with mammographic longest diameter, Lehman said.

For single masses, final MR volume was the strongest correlate for the measurement by the pathologist. After neoadjuvant therapy, the longest diameter measured by MR was the best correlate for pathologic residual disease across all lesions as well as the subgroup of single regional enhancement, she said.

“For all lesion types, longest diameter measured by clinical exam correlated with the pathologic residual disease, though not as strongly as the MR measurement,” she said. “The mammography measurements did not correlate with pathologic residual disease overall or for the subgroups.”