Evaluation of Metastatic Lymph Nodes by Means of FDG PET

Seventeen oncological patients with different tumours were investigated by means of 18fluorodeoxy-D-glucose (FDG) positron emission tomography (PET) for primary staging and restaging after therapeutic interventions. Patients also underwent other staging procedures, including serum tumour marker level determination, radionuclide planar scintigraphy and radiological investigations (ultrasonography, computed tomography and magnetic resonance imaging). The results of different imaging methods in the search for metastatic lymph nodes (LNs) were reviewed. To check the applicability of FDG PET for estimation of the proliferative capacity of the tumours, a comparison was carried out of the patients’ history, results of DNA analysis of the tumour cells and the FDG uptake as measured by PET. FDG PET proved to be superior to conventional imaging methods in staging tumours by the determination of metastatic LNs. Staging by PET was more effective for tumours in the case of LNs localised to the mediastinum (12 cases), the deep (paratracheal and paraoesophageal) cervical (5 cases), the axillary (2 cases), the supraclavicular (1 case) and the iliac regions (1 case). DNA analysis was performed in 14 cases. A direct correlation was found in all but one case between the tumour (LNs) to background FDG uptake ratio (TBUR) and the S-phase proportion of the tumour cells: high (>5) TBUR values were associated with a high (>10%) S-phase proportion, while cases with TBUR ≤5 involved an S-phase fraction of ≤10%. In the 14th case the tumour was aneuploid and a high TBUR value coincided with a low (1%) S-phase proportion. Patients with LNs displaying high TBUR and high S-phase ratio values have a greater chance of developing distant metastases (3/4 cases) than those with low values of both parameters (3/9 cases). An additional advantageous feature of FDG PET is that it can provide individual patient prognoses via estimation of the proliferative capacity of metastatic LNs.