Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography After Concurrent Chemoradiotherapy in Locally Advanced Head-and-Neck Squamous Cell Cancer: The ECLYPS Study

Purpose To assess the standardized implementation and reporting of surveillance [18F]fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scan of the neck in locoregionally advanced head-and-neck squamous cell carcinoma (LAHNSCC) after concurrent chemoradiotherapy (CCRT). Patients and Methods We performed a prospective multicenter study of FDG-PET/CT scanning 12 weeks after CCRT in newly diagnosed patients with LAHNSCC (stage IVa/b) that used standardized reconstruction and Hopkins reporting criteria. The reference standard was histology or > 12 months of clinical follow-up. The primary outcome measure was the negative predictive value (NPV) of FDG-PET/CT scans and other supporting diagnostic test characteristics, including time dependency with increasing follow-up time. Results Of 152 patients, 125 had adequate primary tumor control after CCRT and entered follow-up (median, 20.4 months). Twenty-three (18.4%) had residual neck disease. Overall, NPV was 92.1% (95% CI, 86.9% to 95.3%; null hypothesis: NPV = 85%; P = .012) with sensitivity of 65.2% (95% CI, 44.9% to 81.2%), specificity of 91.2% (95% CI, 84.1% to 95.3%), positive predictive value of 62.5% (95% CI, 45.5% to 76.9%), and accuracy of 86.4% (95% CI, 79.3% to 91.3%). Sensitivity was time dependent and high for residual disease manifesting up to 9 months after imaging but lower (59.7%) for disease detected up to 12 months after imaging. Standardized reporting criteria reduced the number of equivocal reports (95% CI for the difference, 2.6% to 15.0%; P = .003). Test characteristics were not improved with the addition of lymph node CT morphology criteria. Conclusion FDG-PET/CT surveillance using Hopkins criteria 12 weeks after CCRT is reliable in LAHNSCC except for late manifesting residual disease, which may require an additional surveillance scan at 1 year after CCRT to be detected.