PET/CT to Image Hypoxia in Head and Neck Tumours

Patients with head and neck cancer greater than 3 cm will imaged with PET scan and CT scan in order to determine areas of the tumour that are hypoxic. Following surgical removal, samples of the tumour will be evaluated for the expression of hypoxia genes. The preoperative imaging will be compared to the "gold standard" measures of hypoxic response at the level of gene transcription and a new hypoxia marker with the hypoxyprobe detection system (pimonidazole).

Hypothesis: FDG/PET visualization of glycolysis combined with CT visualization of blood flow will correlate with cellular response to hypoxic stress in head and neck tumors and intra-tumor regions. Measurement of relative levels of mRNAs encoding hypoxia response genes will be performed in cells microdissected from the surgical samples. Good correlation between imaging signals and direct molecular measures of hypoxic response in primary human tumors will provide information necessary to develop treatment strategies that employ targeted, increased radiation to hypoxic tumors.

Pimonidazole is an exogenous nitro-imidazole marker, which can be detected through immunohistochemical analysis of frozen sections. It detects cellular hypoxia upon becoming reduced in cells with low oxygen tension, a property that can be detected through antibody mediated detection of the reduced form. It has also shown to reliably and specifically stain hypoxic regions within the tumor, and to correlate well with patient prognosis and treatment outcome.