• Tumour at the primary site 8-10 weeks following radiation; [ Time Frame: 2 years ] [ Designated as safety issue: No ]
• The change in PET signal (standard uptake value; [ Time Frame: 2 years ] [ Designated as safety issue: No ]
• Local recurrence, distant metastases and survival [ Time Frame: 2 years ] [ Designated as safety issue: No ]

• 1.Presence of tumour at the primary site eight to ten weeks following radiation therapy.
• 2.The change in PET signal (standard uptake value)
• 3.Local recurrence, distant metastases and survival

The purpose of this trial is to determine the ability of positron emission tomography (PET) to detect residual cancer in neck lymph nodes of patients following curative treatment with radiation therapy for squamous cell cancer arising in the head and neck.

Patients with head and neck cancer (HNC) undergo treatment of curative intent; patients who are node positive (N2 N3 stages) undergo standard management which includes post-radiation planned neck dissection but two thirds of patients end up not having evidence of residual disease in neck dissection specimens; these patients could have avoided surgery. However, currently used standard tests, like computed tomography (CT) and/or magnetic resonance imaging (MRI) cannot reliably predict who is post-radiation disease free.

PET-Fluorodeoxyglucose scanning is an imaging test based on the increased uptake of radiolabelled glucose by tumour cells. PET might detect neck tumours better than other imaging tests. This is a cohort study in which patients with N2 N3 squamous cell carcinoma of the head and neck undergo a PET and a CT scan at baseline and then post-radiation therapy and chemotherapy. Then, they undergo neck dissection surgery. The PET and CT results are compared with the presence or absence of tumours in the neck nodes. If PET is sufficiently accurate in predicting the presence or absence of tumours in the neck nodes, then a neck dissection could be avoided.

Inclusion Criteria:

All of the following criteria must be satisfied:

1. Histological evidence of squamous cell carcinoma of the head & neck (T1-T4 arising in either the oral cavity, larynx & pharynx, except Nasopharyngeal carcinoma);OR patients with histological evidence of squamous cell carcinoma metastatic to the neck and an unknown primary site after conventional workup without any of the following: i). Clinically suspected skin primary or previous diagnosis of skin cancer arising in the head and neck area; ii). Patients of Asian or African decent -possible nasopharynx primary; iii). Patients whose malignant adenopathy is confined to zone V -possible nasopharynx primary; and iv). Patients whose malignant adenopathy is confined to zone IV (supraclavicular)-possible lung primary.
2. Presence of advanced N2 or N3 neck disease.
3. Planned for primary curative radiation therapy (± chemotherapy) followed by neck dissection eight to twelve weeks after completion of treatment.

Exclusion Criteria:

1. Presence of distant metastasis
2. Recurrent tumour
3. Prior neo-adjuvant chemotherapy
4. Previous radiation therapy to intended treatment volumes
5. Other active malignancy
6. Surgically inoperable neck disease
7. Unable to remain supine for 60 minutes
8. Unfit to undergo general anesthetic or neck dissection for medical reasons
9. Known hypersensitivity to CT contrast
10. Pregnancy