Prognostic value of response assessment fluorodeoxyglucose positron emission tomography-computed tomography scan in radically treated squamous cell carcinoma of head and neck: Long-term results of a prospective study

Objective: The objective of this study is to evaluate the diagnostic and prognostic ability of fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) scan in patients with squamous cell carcinoma of the head and neck treated with chemoradiotherapy or radiotherapy only. Materials and Methods: Fifty-nine patients with HNSCC planned for radical nonsurgical treatment were randomized to receive either three-dimensional conformal radiotherapy or intensity-modulated radiation therapy. In addition to routine clinical examination and staging investigations, patients had a FDG PET-CT scan at baseline and on the first follow-up for response assessment. No evidence of clinicopathological disease for at least 6 months after the completion of treatment was considered confirmation of complete response. The presence or absence of disease during the follow-up period was used to calculate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PET-CT for the primary site and node. Results: At a median follow-up of 52.5 months, 55.6% of patients were alive and disease free. Response assessment PET-CT was done at a median of 9 weeks (range: 5u18 weeks). PET-CT assessment of the primary had sensitivity, specificity, PPV, and NPV of 81.8%, 93%, 75%, and 95.2%, respectively; the corresponding figures at the node were 44.4%, 95.6%, 66.7%, and 89.6%. The median baseline maximum standardized uptake value (SUVmax) at primary and node was 14.9 and 8.1, respectively. When PET-CT was done after 10 weeks, no false-positive or false-negative findings were seen. Patients with negative PET at the first follow-up had a significantly better progression-free and overall survival. Conclusions: Disease evaluation using PET-CT has an overall accuracy of 80%. High baseline SUVmax correlates with worse clinical outcomes. Negative PET-CT at the first follow-up is a predictor for survival.