Potential for truncating the scan length of restaging FDG-PET/CT after chemoradiotherapy in head and neck squamous cell carcinoma.

Background: Fluorine-18 fluorodeoxyglucose PET/computed tomography (CT) is now routinely used for staging and monitoring treatment response in head and neck squamous cell carcinoma (HNSCC). Although most patients with HSNCC have locoregional disease, distant metastases are relatively uncommon and occur predominantly in the lungs.

Aim: To explore the potential of a limited scan range from the skull vertex to lung bases, viz. an 'above diaphragm' scan, as an adequate examination for assessment of disease following chemoradiotherapy.

Methods: A retrospective review of 240 patients with HNSCC both staged and monitored after therapy with (18)F-fluorodeoxyglucose PET/CT was conducted. Patients with previous HNSCC, unknown primary and known distant metastatic disease were excluded. Patients with positive PET/CT findings below the neck on the posttherapy study were confirmed on either follow-up clinical or radiological findings.

Results: A total of 196 (81.7%) patients had nodal disease at PET/CT staging. Unrelated findings were present in 50 (20.8%) patients, including five colonic neoplasms and two second malignancies. After an average of 6.4 months after staging, 13 patients (5.4%) demonstrated progression to distant metastases on the posttherapy PET/CT. All patients demonstrated intrapulmonary metastases. Two patients had additional liver metastases, which would not have impacted on the overall management. No patient demonstrated isolated disease below the diaphragm.

Conclusion: A limited 'above-diaphragm' scan for early assessment following chemoradiotherapy may be safely considered. The benefits of this tailored approach flow onto both the health system and the patients as it can improve resource allocation by increasing scanner availability and patient throughput and reduces cumulative patient radiation exposure.