Overview of the clinical effectiveness of positron emission tomography imaging in selected cancers.	OBJECTIVES: To assess the clinical effectiveness of positron emission tomography (PET) using 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in breast, colorectal, head and neck, lung, lymphoma, melanoma, oesophageal and thyroid cancers. Management decisions relating to diagnosis, staging/restaging, recurrence, treatment response and radiotherapy (RT) planning were evaluated separately. DATA SOURCES: Major electronic databases were searched up to August 2005 and a survey of UK PET facilities was performed in February 2006. REVIEW METHODS: This assessment augments the systematic search undertaken in a previous review. Studies were limited to those using commercial dedicated PET or PET/computed tomography (CT) devices with FDG, in one of the eight cancers. RESULTS: The new search identified six systematic reviews and 158 primary studies. An economic model for England showed that in non-small cell lung cancer (NSCLC) FDG-PET was cost-effective in CT node-negative patients, but not in CT node-positive patients. A less robust model also showed that FDG-PET was cost-effective in RT planning for NSCLC. A model for Scotland showed that in late-stage Hodgkin's lymphoma (HL), FDG-PET was cost-effective for restaging after induction therapy. For staging/restaging colorectal cancer, FDG-PET changed patient management in a way that can impact on curative therapy. For detection of solitary pulmonary nodule (SPN) there was also impact on patient management, but the resulting effect on patient outcomes was unclear. FDG-PET had an impact on patient management across paediatric lymphoma decisions, but further study of individual management decisions is required. For other cancer management decisions, the evidence on patient management is weak. FDG-PET was accurate in detecting distant metastases across several sites, but sensitivity was variable for detection of lymph-node metastases and poor in early stage disease where sentinel lymph-node biopsy would be used and for small lesions. There were 61 studies of treatment response. These were generally small and covered all cancers except melanoma. They showed that FDG-PET imaging could be correlated with response, in some cases, but the impact on patient management was not documented. There were 17 small studies of RT planning in four cancers; here, FDG-PET led to alteration of RT volumes and doses, but the impact on patient outcomes was not studied. FDG-PET improved diagnostic accuracy compared with alternatives in a number of other cancer management decisions, but more comparative evidence is needed. There were 23 studies of PET/CT in six cancers (excluding breast and melanoma). In these FDG-PET/CT generally improved accuracy by 10-15% over PET, resolving some equivocal images. The survey of PET facilities in the UK showed that PET and PET/CT are being used for a variety of cancer indications. PET facilities are not distributed evenly across the UK and use is inconsistent. Various research studies are underway in most centres, but only a few of these are collaborative studies. There is major variation in throughput and cost per scan (635-1300 pounds). CONCLUSIONS: The strongest evidence for the clinical effectiveness of FDG-PET is in staging NSCLC, restaging HL, staging/restaging colorectal cancer and detection of SPN. Some of these may still require clinical audit to augment the evidence base. Other management decisions require further research to show the impact of FDG-PET on patient management or added value in the diagnostic pathway. It is likely that capital investment will be in the newer PET/CT technology, for which there is less evidence. However, as this technology appears to be slightly more accurate than PET/CT, the PET clinical effectiveness results presented here can be extrapolated to cover PET/CT. PET research could be undertaken on FDG-PET or FDG-PET/CT, using a standard cancer work-up process on typical patients who are seen within the NHS in England. For treatment response and RT planning, the need for larger studies using consistent methods across the UK is highlighted as a priority for all cancers. For all studies, consideration should be given to collaboration across sites nationally and internationally, taking cognisance of the work of the National Cancer Research Institute.	esophagus