Date Published: July 12, 2016
Publisher: Springer US
Author(s): Pavel Fencl, Otakar Belohlavek, Tomas Harustiak, Milada Zemanova.
The aim of the analysis was to assess the accuracy of various FDG-PET/CT parameters in staging lymph nodes after neoadjuvant chemotherapy.
In this prospective study, 74 patients with adenocarcinoma of the esophageal–gastric junction were examined by FDG-PET/CT in the course of their neoadjuvant chemotherapy given before surgical treatment. Data from the final FDG-PET/CT examinations were compared with the histology from the surgical specimens (gold standard). The accuracy was calculated for four FDG-PET/CT parameters: (1) hypermetabolic nodes, (2) large nodes, (3) large-and-medium large nodes, and (4) hypermetabolic or large nodes.
In 74 patients, a total of 1540 lymph nodes were obtained by surgery, and these were grouped into 287 regions according to topographic origin. Five hundred and two nodes were imaged by FDG-PET/CT and were grouped into these same regions for comparison. In the analysis, (1) hypermetabolic nodes, (2) large nodes, (3) large-and-medium large nodes, and (4) hypermetabolic or large nodes identified metastases in particular regions with sensitivities of 11.6%, 2.9%, 21.7%, and 13.0%, respectively; specificity was 98.6%, 94.5%, 74.8%, and 93.6%, respectively. The best accuracy of 77.7% reached the parameter of hypermetabolic nodes. Accuracy decreased to 62.0% when also smaller nodes (medium-large) were taken for the parameter of metastases.
FDG-PET/CT proved low sensitivity and high specificity. Low sensitivity was based on low detection rate (32.6%) when compared nodes imaged by FDG-PET/CT to nodes found by surgery, and in inability to detect micrometastases. Sensitivity increased when also medium-large LNs were taken for positive, but specificity and accuracy decreased.
The exclusive selection of patients does not allow a general conclusion for all esophageal cancers to be drawn; on the other hand, our data were not subject to variability due to biologically different cancers in different localizations.
In a homogenous group of 74 patients with adenocarcinoma of the esophageal–gastric junction, nodal staging by FDG-PET/CT was not accurate due to the inability of FDG-PET/CT to image all lymph nodes and to verify micrometastases or metastases in small lymph nodes. The parameter “hypermetabolic nodes” proved to be of low sensitivity, but high specificity due to the low number of false-positive findings. Inflammation in lymph nodes mimicking metastases played a marginal role in this group of patients. The parameters “large nodes”, “large-and-medium large nodes”, and “large or hypermetabolic nodes” did not improve accuracy for low sensitivity, low specificity, or both. Due to low sensitivity, negative FDG-PET/CT findings could not exclude the presence of metastases; high specificity indicates that any positive nodal staging must be carefully considered.