Dual time point ¹⁸F-fluorodeoxyglucose-positron emission tomography-computed tomography imaging in characterization of axillary node in breast cancer patients and its correlation to sentinel node biopsy and final histopathology

The purpose of this study was to assess the utility of dual-time-point ¹⁸F-FDG PET-CT imaging for characterization of axillary lymph nodes in breast cancer patients and correlate with sentinel node and final histopathological examination. 35 patients with biopsy proven breast cancer presented for ¹⁸F-FDG PET-CT study were included in the study. They underwent PET-CT scans at 60 min and 120 min post FDG injection. From this, the percentage change in standardized uptake value (∆%SUV max) between first and delayed scan was calculated for the axillary nodes. A cutoff value of change in SUV max of 5%, 10%, 15%, 20%, 25% and 30% was taken into account and the sensitivity, specificity, PPV, NPV and accuracy was calculated. The patients underwent sentinel node dissection and the FDG uptake in nodes was correlated with the result of frozen section and final histopathology. Results: 55 nodes were removed during surgery as sentinel nodes, of which, 33 were positive for metastases. The cutoff value of 15% ∆%SUV max for nodes showed the maximum accuracy when correlated with the sentinel node frozen section and on ROC analysis. There was a positive correlation between the positivity of nodes and SUV max of nodes in first scan (r = 0.4424; P < 0.05) and to ∆%SUV max of nodes (r = 0.3227, P < 0.05). Eight nodes showed micro metastases on final histopathology, all of which showed increase of ∆%SUV max. Distant metastases, not previously known, were seen in 8 patients. FDG PET-CT dual point imaging can be used to differentiate between malignant and benign nodes and 15% percentage increase in SUV max of axillary nodes showed maximum accuracy to differentiate between malignant and benign nodes. (author)