Role of dual time point FDG PET imaging in differentiating axillary lesion in breast cancer

Objectives This prospective study was aimed to determine if dual time point imaging can improve the sensitivity and the specificity of PET for detection of axillary metastatic lesions.

Methods Newly diagnosed 180 breast cancer patients underwent dual time point PET (SUVmax) was measured from axillary lesion from both time points. The percent change in SUVmax (▵%SUVmax) between first and second scans(SUVmax1 and SUVmax2) was calculated. Sentinel node biopsy was performed. True and false positive rates were calculated according to pathology and SUV calculations were compared .

Results Dual time PET findings were positive for axillary metastasis in 45 patients, 27 of them had axillary metastasis confirmed by histopathology while 18 were found to be false positive likely due to diagnostic biopsy. The SUVmax1, SUVmax2 and ▵%SUVmax were 3.5±2.2, 4.0±2.5 and 8.9±12.5% in true positive group while those were 2.1±2.2, 2.1±2.0 and ─0.4±25.1% in false positive group, respectively. The comparisons were significant (p=0.006, p=0.001 and 0.043, respectively) .

Conclusions The true positive axillary metastatic lesions had higher SUVmax values and showed an increase over time while false positive lesions had lower SUVmax and was either stable or showed a decrease over time. Dual time point imaging may allow differentiating true positive axillary metastasis from false positive nodes.