The value of dual-time-point18F-FDG PET/CT for identifying axillary lymph node metastasis in breast cancer patients

Objective: The sensitivity of 18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) for detecting axillary lymph node (ALN) metastases in breast cancer is reported to be low. Several studies have shown, however, that dual-time-point 18F-FDG PET imaging provides improved accuracy in the diagnosis of certain primary tumours when compared with single-scan imaging. The purpose of this study was to assess whether the use of dual-time-point 18F-FDG PET/CT scans could improve the diagnostic accuracy of ALN metastasis in breast cancer. Method: The study included 171 breast cancer patients who underwent pre-operative 18F-FDG PET/CT scans at 2 time-points, the first at 1 h after radiotracer injection and the second 3 h after injection. Where 18F-FDG uptake was in the ALN perceptibly increased, the maximum standardised uptake values for both time-points (SUVmax1 and SUVmax2) and the retention index (RI) were calculated. Correlation between the PET/CT results and post-operative histological results was assessed. Results: The performance of 1 h and 3 h PET/CT scans was equal, with sensitivity 60.3% and specificity 84.7%, in detecting ALN metastasis. Out of 171 patients, 60 had ALNs with increased 18F-FDG uptake on 1 h or 3 h images. There was no significant difference in RI between the metastatic ALN-positive group and the node-negative group. The area under the receiver operating characteristic (ROC) curve for SUVmax1 was 0.90 (p<0.001) and 0.87 for SUVmax2 (p<0.001). Conclusion: Dual time-point imaging did not improve the overall performance of 18F-FDG PET/CT in detecting ALN metastasis in breast cancer patients.