How the Council reached the recommendation

1. The Council noted that patient co-morbidities may impact on the clinical utility of FDG-PET, for example people with poorly controlled diabetes may not be suitable for a glucose-based radiotracer. In these circumstances, SPECT is an appropriate alternative.
2. Given that the current FDG-PET service is delivered from four centres in Scotland, the Council noted that some people may have to travel for PET scans and this has the potential to create inequalities in access. SPECT is widely available in Scotland.
3. Depending on how many people undergoing investigations for dementia would benefit from FDG-PET scanning, the Council acknowledged that the infrastructure and resource investment could be significant. The PET-CT service is already stretched in Scotland, with approximately 700 scans being done a month (mostly for people with cancer or suspected cancer). Based on the number of people with dementia, or suspected dementia, who are currently referred for a SPECT scan in Scotland, a clinical expert estimated that approximately 20 people per month may be eligible for FDG-PET scanning. This number may change considerably depending on developments in the diagnosis and treatment of dementia, and whether these developments impact the demand for nuclear imaging.
4. The Council agreed that the clinical-effectiveness evidence published since 2018 is limited in quality and quantity. The studies identified focused on diagnostic accuracy, and it is not clear how the addition of FDG-PET to the diagnostic pathway impacts on clinical decision-making, the treatments that patients with dementia are offered, and the outcomes for patients. The heterogeneity between the studies means that robust conclusions are not possible. The Council also recognised the absence of cost-effectiveness evidence.
5. The Council noted that FDG-PET services for dementia are commissioned in NHS England, NHS Wales and NHS Northern Ireland. NHSScotland does not commission FDG-PET services for dementia even though the guidance in place in NHSScotland matches the guidance in the other UK nations. The Council also noted a lack of available information on the impact of FDG-PET for dementia diagnosis in other parts of the UK, either service delivery implications or patient outcomes.
6. The Council noted that the diagnosis and treatment landscape for dementia is evolving rapidly. In addition to the possible availability of disease-modifying dementia drugs in the coming years, other areas of potential development include the application of precision medicine. Given this fast-changing landscape, it is difficult to predict exactly how the demand for nuclear imaging for dementia will change in the near future.
7. The Council recognised that the experience for patients undergoing an FDG-PET or SPECT scanning may differ, but that both scans are likely to create an additional stress for people who may already feel they are in a difficult and frightening place. The Council reiterated that scans should only be used when there is a likely impact on patient management decisions.
8. Following insight from a topic expert, the Council noted:
   • there is a need for good quality evidence, particularly evidence that directly compares perfusion SPECT with FDG-PET in this patient group
   • there is a need to consider why the service in NHSScotland differs from the other UK nations
   • FDG-PET scans generally take 10 minutes, whereas SPECT scans take approximately 30 to 45 minutes
   • FDG-PET scan images are generally easier to report on, compared with SPECT scan images
   • the images produced from SPECT scanning have improved over the years as the technology advances, but we cannot be confident how image quality compares with FDG-PET image quality.

Date of publication: 16 December 2024