FDG PET using SUVmax for preoperative T-staging of esophageal squamous cell carcinoma with and without neoadjuvant chemoradiotherapy

BACKGROUND Accurate T-staging is pivotal for predicting prognosis and selecting appropriate therapies for esophageal squamous cell carcinoma (ESCC). The diagnostic performance of fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for its T-staging is uncertain. We investigated use of FDG PET/CT for preoperative T-staging of patients with ESCC. METHODS Patients with ESCC given preoperative FDG PET/CT scans, either with (CRT[+] group) or without (CRT[-] group) neoadjuvant chemoradiotherapy, were retrospectively reviewed. Maximal standardized uptake value (SUVmax) of the primary tumors on FDG PET/CT scans were measured, and histopathological results were used as the reference standard. The associations between pathological T-stage and potential factors of age, tumor location, tumor grade, tumor size, and tumor SUVmax were analyzed. The cut-off levels of SUVmax for predicting different T-stages and for residual viable tumors after neoadjuvant chemoradiotherapy were determined using receiver operating characteristic analyses. RESULTS We enrolled 103 patients (45 in the CRT[-] group; 58 in the CRT[+] group). SUVmax, an independent predictive factor, positively correlated with the pathological T-stage in both groups (CRT[-] group: ρ = 0.736, p < 0.001; and CRT[+] group: ρ = 0.792, p < 0.001). The overall accuracy of the PET/CT with thresholded SUVmax for predicting the pathological T-stage was 73.3% in the CRT[-] group (SUVmax of T0: 0-1.9, T1: 2.0-4.4, T2: 4.5-6.5, T3: 6.6-13.0, T4: >13.0) and 67.2% in the CRT[+] group (SUVmax of T0: 0-3.4, T1: 3.5-3.9, T2: 4.0-5.5, T3: 5.6-6.2, T4: > 6.2). For CRT[-] group, the accuracy using an SUVmax cut-off of 4.4 to differentiate early (T0-1) from locally advanced disease (T2-4) was 82.2% (95% CI, 71.1-93.4%). For CRT[+] group, the accuracy using an SUVmax cut-off of 3.4 to predict residual viable tumors (non-T0) after completion of chemoradiotherapy was 82.8% (95% CI, 73.0-92.5%). CONCLUSIONS The FDG avidity of a primary esophageal tumor significantly positively correlated with the pathological T-stage. PET/CT with thresholded SUVmax was useful for predicting T-stage and differentiating residual viable tumors.