Can hybrid FDG-PET/CT detect subclinical lymph node metastasis of esophageal cancer appropriately and contribute to radiation treatment planning? A comparison of image-based and pathological findings.

BACKGROUND

We aimed to determine the appropriateness of adding 18F-fluorodeoxyglucose (FDG)-positronemission tomography (PET) to computed tomography (CT) and other pre-existing diagnostic imaging modalities for detecting subclinical lymph node metastasis of esophageal cancer, by comparing images from these modalities with the results of histopathological analysis.

METHODS

Twenty patients who received radical surgery for squamous cell carcinoma of the esophagus were examined by PET-CT, and endoscopic ultrasound (EUS) examination before surgery. Based on these diagnostic modalities, the clinical target volume (CTV) was set as the gross tumor volume (GTV) plus a 1-cm margin. Histopathological diagnosis was performed in all patients immediately after resection.

RESULTS

Fifty-three (3.0%) of 1764 nodes in the 20 patients were histopathologically positive for cancer cells. The CTV was not adequate to cover these histopathologically detected positive lymph nodes in 8 of 20 patients on CT, 5 of 20 on CT+EUS, 7 of 20 on PET-CT, and 5 of 20 on PET-CT+EUS.

CONCLUSION

The detection rate of subclinical lymph node metastasis did not improve with the use of PET-CT, for either the cervical and supraclavicular, mediastinal, or abdominal regions. It is not recommended to use FDG-PET or PET-CT alone as a diagnostic tool to determine CTV if pathologically involved lymphatic regions are to be included in the CTV in the treatment protocol. The accuracy of PET-CT must be further improved in order to better detect positive nodes and improve the definition of the CTV.