Usefulness of combined PET/CT to assess regional lymph node involvement in gastric cancer

The aim of this study was to evaluate the value of positron emission tomography/computed tomography (PET/CT) for preoperative staging of gastric cancer and to compare the diagnostic performance of PET/CT with that of contrast-enhanced computed tomography (CECT).

We retrospectively reviewed 74 gastric cancer patients who underwent preoperative PET/CT and CECT, and subsequent curative surgical resection between April 2007 and July 2011. Preoperative PET/CT and CECT images for primary tumors of the stomach and lymph node metastases were reviewed retrospectively. The final diagnoses of primary tumors and LN metastases were based on histopathological specimens in all patients.

Advanced gastric cancer was present in 65% of patients (n = 48), and the remaining patients had early gastric cancer (n = 26). Sixteen patients (22%) showed signet-ring-cell histology. For the detection of the primary tumor, the sensitivity of PET/CT was significantly higher than that of CECT (67% vs 55%, respectively; P = 0.049). For the evaluation of regional lymph node metastasis, the sensitivity, specificity, and accuracy of PET/CT and CECT were 34% and 51% (P = 0.065), 88% and 79% (P = 0.687), and 58% and 64% (P = 0.332), respectively. Neither PET/CT nor CECT detected regional lymph node metastases in early gastric cancer patients. Signet-ring-cell histology showed trends of non-FDG-avid lymph node metastases (odds ratio = 0.15, 95% confidence interval 0.17-1.37, P = 0.093).

The accuracy of PET/CT is low and it is not a useful tool in the staging of gastric cancer overall in early gastric cancer and in signet-ring-cell carcinoma. Furthermore, the sensitivity of PET/CT could be inferior to that of CECT in the diagnosis of regional lymph node metastasis.