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In prostate cancer, use of FDG, the radiopharmaceutical currently most widely used in oncology, is limited to the most aggressive cancers and, in the absence of another tracer, to attempting to localise occult recurrences detected biochemically (elevated PSA serum levels). Four other PET tracers are currently suggested in various situations of prostate cancer development: for guiding biopsies, for diagnosis and staging of the primary cancer and of local or metastatic recurrences, especially in bone, and for localizing occult biochemical recurrence. This article is illustrated by cases summarising our experience with fluoromethylcholine-(18F) and PET/CT. They cover a wide spectrum of clinical settings: localisation of intraprostatic neoplastic lesions, initial staging, monitoring treatment by ultrasound, detection of occult recurrences and characterisation of images on conventional imaging modalities, which are questionable or difficult to interpret.

FDG PET is useful when cancer in the head or neck (except for tumors of the salivary glands, which cannot be characterized accurately) is diagnosed or suspected but not confirmed by biopsy. It can, for example, find evidence of suspicious lymph nodes in clinically N0 necks, detect foci suggestive of distant metastases or second cancers, and provide useful prognostic information. Because it can be very difficult to identify anatomical structures and landmarks on PET images in the head and neck region, PET/CT fusion is very helpful in this area. In early assessment of chemotherapy, the absence of a significant reduction in FDG uptake after one or two cycles predicts lack of efficacy and thus indicates the need to modify the regimen. Conversely, the disappearance of FDG foci indicates effective treatment and good prognosis but cannot rule out the persistence of any malignant tissue at the end of treatment, especially neoadjuvant. Diagnostic impact is probably greatest in monitoring for recurrence and restaging known recurrence: FDG PET should be performed - perhaps routinely - early enough that curative options are still open, but long enough after the end of treatment to avoid false positive results from inflammation. The strategy and timing of FDG PET during follow-up should be determined in more detail in the future, as should the role (if any) of fluorotyrosine (FET) PET in squamous cell carcinoma.