Purpose:

To compare magnetic resonance (MR) imaging  ndings and clinical assessment for prediction of pathologic re- sponse to neoadjuvant chemotherapy (NACT) in patients with stage II or III breast cancer.

Materials and Methods:

The HIPAA-compliant protocol and the informed consent process were approved by the American College of Radiol- ogy Institutional Review Board and local-site institutional review boards. Women with invasive breast cancer of 3 cm or greater undergoing NACT with an anthracycline- based regimen, with or without a taxane, were enrolled between May 2002 and March 2006. MR imaging was per- formed before NACT ( rst examination), after one cycle of anthracyline-based treatment (second examination), between the anthracycline-based regimen and taxane (third examination), and after all chemotherapy and prior to surgery (fourth examination). MR imaging assessment included measurements of tumor longest diameter and volume and peak signal enhancement ratio. Clinical size was also recorded at each time point. Change in clinical and MR imaging predictor variables were compared for the ability to predict pathologic complete response (pCR) and residual cancer burden (RCB). Univariate and mul- tivariate random-effects logistic regression models were used to characterize the ability of tumor response mea- surements to predict pathologic outcome, with area under the receiver operating characteristic curve (AUC) used as a summary statistic.

Results:

Data in 216 women (age range, 26–68 years) with two or more imaging time points were analyzed. For predic- tion of both pCR and RCB, MR imaging size measure- ments were superior to clinical examination at all time points, with tumor volume change showing the greatest relative bene t at the second MR imaging examination. AUC differences between MR imaging volume and clinical size predictors at the early, mid-, and posttreatment time points, respectively, were 0.14, 0.09, and 0.02 for pre- diction of pCR and 0.09, 0.07, and 0.05 for prediction of RCB. In multivariate analysis, the AUC for predicting pCR at the second imaging examination increased from 0.70 for volume alone to 0.73 when all four predictor variables were used. Additional predictive value was gained with adjustments for age and race.

Conclusion:

MR imaging  ndings are a stronger predictor of patho- logic response to NACT than clinical assessment, with the greatest advantage observed with the use of volumetric measurement of tumor response early in treatment.