Utility of MRI and PET/CT after neoadjuvant chemotherapy in breast cancer patients: correlation with pathological response grading system based on tumor cellularity

Abstract

MRI and PET/CT are useful for assessing breast cancer patients after neoadjuvant chemotherapy (NAC). To investigate the utility of MRI and PET/CT in the prediction of pathologic response to neoadjuvant chemotherapy using Miller-Payne grading system in patients with breast cancer. From January 2008 to December 2010, 59 consecutive patients with pathologically proven breast cancer, who underwent neoadjuvant chemotherapy followed by surgery were retrospectively enrolled. The maximal diameter decrease rate and volume reduction rate by three-dimensional (3D) MRI and standardized uptake value (SUV) reduction rate by PET/CT were calculated and correlated with the Miller-Payne grading system using the Spearman rank correlation test. Patients with Miller-Payne grades 1 or 2 were classified into the non-responder group and patients with grades 3, 4, and 5 were in the responder group. To differentiate between responders and non-responders, receiver-operating characteristic (ROC) analysis was performed. The volume reduction rate was 64.87 ± 46.95, diameter decrease rate was 48.09 ± 35.02, and SUV decrease rate was 62.10 ± 32.17. Among three parameters, the volume reduction rate was most correlated with histopathologic grades of regression (ρ = 0.755, P < .0001) followed by diameter decrease rate (ρ = 0.660, P < 0.0001), and SUV decrease rate of primary breast mass (ρ = 0.561, P = 0.0002). The area under the ROC curve (Az) value was largest in the volume reduction rate (Az = 0.9), followed by SUV decrease rate (Az = 0.875), and diameter decrease rate (Az = 0.849). The best cut-offs for differentiating responders from non-responders in the ROC curve analysis were a 50% decrease in diameter, 68.9% decrease in volume, and 60.1% decrease in SUV after NAC. Volumetric measurement using 3D MRI combined with conventional diameter measurement may be more accurate to evaluate pathologic response after NAC.