The presence of lymph node spread of head and neck tumours is associated with substantially worse prognosis, and clinical examination and imaging techniques (CT and MRI) detect fewer than 50% of involved lymph nodes, which may result in unnecessary neck surgery. In patients with head and neck tumours studied prior to initial surgery, the sensitivity and specificity of [18F]-FDG PET in detecting nodal metastases has been reported ranging from 71 to 91%, and 88-100%, respectively (Fig. 16.7) [8, 80-83]. Metastatic disease outside the neck can also be identified with [18F]-FDG PET scans . Primary tumours can also be detected with a similar sensitivity to CT/MRI. In patients studied after initial treatment of metastatic nodal disease with radiotherapy, [18F]-FDG PET is often accurate only after a three month period [20, 85-87]. This has been shown to be due to the effects of stunning of tumour cells, where the metabolic rate and proliferation of cancer cells may be suppressed after radiotherapy, as well as the possible presence of microscopic disease only after radiotherapy treatment which is below the resolution of the PET camera. In both patient groups, the accuracy of [18F]-FDG PET has the potential to direct surgeons to otherwise unknown sites of metastatic disease, as well as avoiding surgery in areas of the neck where [18F]-FDG PET scans show negative results. [18F]-FDG PET has also been shown to be a prognostic factor for radiotherapy response . In patients with advanced loco-regional head and neck cancer, radiotherapy treatment planning incorporating [18F]-FDG PET information has emerged as an exciting new method of potentially improving response rates.
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Metabolism. There isn’t perhaps a more frequently used word in the weight loss (and weight gain) vocabulary than this. Indeed, it’s not uncommon to overhear people talking about their struggles or triumphs over the holiday bulge or love handles in terms of whether their metabolism is working, or not.