Diagnostic performance of response assessment FDG-PET/CT in patients with head and neck squamous cell carcinoma treated with high-precision definitive (chemo)radiation

PurposeTo prospectively assess diagnostic performance of response assessment fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in patients with HNSCC treated with high-precision definitive (chemo)radiation.MethodsFifty-seven patients treated on a prospective clinical trial having post-treatment response assessment FDG-PET/CT scans were included. Clinico-pathologic findings and follow-up information was considered as reference standard.ResultsFirst response assessment FDG-PET/CT was done at a median of 9 weeks (inter-quartile range 8–10 weeks) from completion of treatment. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of first response assessment FDG-PET/CT for identifying residual disease at primary site was 50%, 91.8%, 50%, 91.8%, and 86%. The corresponding figures for the neck were 62.5%, 98%, 83.3%, 94.1%, and 93%. With a median follow-up of 26 months (range 7–45 months), the 3-year loco-regional control (83.9% vs 58.3%, p = 0.001) and overall survival (68.8% vs 58.3%, p = 0.063) was significantly better in patients with negative response assessment scans.ConclusionThe overall diagnostic accuracy of response assessment FDG-PET/CT is good, but its sensitivity and PPV is somewhat low, particularly for primary site. A negative response assessment FDG-PET/CT scan is highly suggestive of absence of viable disease that could be used to guide decision-making.