Preoperative staging of clinically node-negative esophageal cancer by the combination of ¹⁸F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG–PET/CT)

Although lymph node metastasis is a significant prognostic factor in patients with esophageal cancer, the sensitivity and specificity of conventional imaging modalities such as computed tomography (CT) and magnetic resonance imaging is limited in the diagnosis of lymph node metastasis. This retrospective study examined the usefulness of the combination of ¹⁸F-fluorodeoxyglucose-positron emission tomography (PET)/CT in the diagnosis of subclinical lymph node metastasis from esophageal cancer.

We compared the postoperative pathological findings and preoperative PET/CT findings in 81 consecutive clinically node-negative esophageal cancer patients who underwent esophagectomy with lymphadenectomy. All patients had resectable tumor (T1–T3) and were node-negative based on preoperative conventional examinations.

Of the 81 patients, 37 had pathological node metastasis in surgical specimens. A PET/CT diagnosis of node metastasis was made using several cut-off values of the maximum standardized uptake value (SUV_max). The sensitivity, specificity, and accuracy of PET/CT diagnosis were 32.4, 70.4, and 53.1 % at an SUV_max cut-off value of 1.8; 29.7 %, 79.5 %, and 56.8 % at 2.0; 21.6 %, 90.9 %, and 59.3 % at 2.5; 16.2 %, 95.4 %, and 59.3 % at 3.0; and 10.8 %, 97.7 %, and 56.8 % at 3.5, respectively. When an SUV_max cut-off value of 1.8 was employed, the disease-free survival rate was significantly worse in PET/CT-node-positive patients (PET-N(+)) than in PET-N(−) patients. Next, the effect of PET-N status on the prognosis was analyzed in pN(−)and pN(+) patients separately. Among the 44 pN(−) patients, PET-N status did not significantly affect the disease-free survival (p = 0.879). In contrast, in the 37 pN(+) patients, DFS was significantly better in PET-N(−) patients than in PET-N(+) patients (p = 0.002).

The diagnostic sensitivity of PET/CT for subclinical lymph node metastasis in clinically node-negative patients is low, but this combined modality can potentially identify patients with poor prognosis.