Table 7.

Summary: recommendations and key issues

1.	Unknown primary: 18F-FDG-PET/CT is recommended to identify primary tumours in patients presenting with cervical lymph node metastases with unknown primary
2.	Pre-treatment staging: Multiple studies have demonstrated that adding PET (or PET/CT) to a conventional work-up resulted in a higher staging accuracy; nodal classification is improved, especially in terms of specificity; and 18F-FDG-PET or PET/CT detects more distant metastases and second malignancy than conventional staging
3.	Clinical impact: A more refined staging has demonstrated to have clinical impact on treatment decisions. PET/CT should be included in the routine diagnosis of patients with Stages III–IV HNSCC, as it significantly improves staging accuracy and also has a marked impact on management plans. However, there is no evidence with regard to a possible benefit in outcomes due to PET/CT
4.	Radiotherapy: The use of 18F-FDG-PET translates into smaller GTV for the primary tumour volumes than with the use of CT or MRI. PET can complement other diagnostic imaging modalities for management decisions and guidance of radiotherapy planning, but it cannot replace physical examination or MRI/CT. There is no current standardized method for functional volume segmentation recommended for daily practice
5.	Monitoring response to treatment: PET/CT is recommended to check for residual disease at least 8 and, preferably, 12–16 weeks after definitive chemoradiotherapy in node-positive HNSCC (NPV >90%), avoiding unnecessary neck dissections in patients presenting complete response. Mehanna et al103 indicated that patients with incomplete (presenting high 18F-FDG uptake at 12 weeks after chemoradiotherapy, with or without enlarged lymph nodes in the neck), or equivocal response (mild or no 18F-FDG uptake in enlarged nodes or mild 18F-FDG uptake in normal-sized nodes) should undergo neck dissection. Few patients in this trial had N3 (Stage IVb) disease [17/564 (3%)]. Therefore, a PET-CT-guided surveillance policy to patients presenting N3 disease is not currently justified due to the small number of patients presenting N3 disease in this study
6.	Surveillance: PET/CT is not indicated in routine follow-up
7.	Prognosis: Patients presenting increased SUV (SUVmax, SUVmean) or higher MTV or TLG seem to have worse prognosis (higher risk of treatment failure). There is no currently evidence to support that this type of patients should receive different treatment approach. Nevertheless, these parameters could be used to stratify patients in future clinical trials
8.	To further validate incorporating PET/CT into daily practice also, clinical effect on outcomes and cost effectiveness should be reflected in clinical studies

¹⁸F-FDG, fluorine-18 fludeoxyglucose; GTV, gross tumour volume; HNSCC, head and neck squamous cell carcinoma; MTV, metabolic tumour volume; NPV, negative-predictive value; PET, positron emission tomography; SUV, standardized uptake value; SUV_max, maximal SUV; SUV_mean, mean SUV; TLG, total lesion glycolysis.