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

Abstract

BACKGROUND: MRI and PET/CT are useful for assessing breast cancer patients after

neoadjuvant chemotherapy (NAC). PURPOSE: 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. MATERIAL AND METHODS:

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. RESULTS: 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 (rho = 0.755, P < .0001) followed by

diameter decrease rate (rho = 0.660, P < 0.0001), and SUV decrease rate of

primary breast mass (rho = 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. CONCLUSION: Volumetric measurement using 3D MRI

combined with conventional diameter measurement may be more accurate to evaluate

pathologic response after NAC.