Clinical Applications of PET in Cancer
PET is used in the following ways:
- Initial diagnosis (benign/malignant disease, grade of malignancy)
- Staging (assessing the extent of disease)
- Monitoring of response to therapy
- Residual vs. active disease after chemotherapy/radiotherapy
- Recurrence/restaging of disease after therapy
- Identification of the primary site of the tumour
- Treatment planning for radiotherapy
Currently, evidence for the benefit of using PET is strong in several cancer types, notably lung cancer, lymphoma and colorectal cancer. There are also encouraging results in a large number of other tumour types and this list is likely to grow dramatically. The Evidence-based indications for the use of PET-CT in the United Kingdom are available on the Royal College Of Radiologists website.
Research Applications of PET in Cancer
PET has great potential to improve the management of patients with cancer and the evaluation of new anti-cancer drugs with the aim of making new therapies available in the clinic more rapidly. Most PET research in cancer falls into one of the following areas:
- Assessment of the utility of PET in patient management
- Facilitating the development of new anti-cancer drugs
- Translational research Development of new PET technology and radiopharmaceuticals
Assessment of the Utility of PET in Patient Management
PET already has an established role in the management of patients with a wide variety of cancers. The areas where it is most useful are in staging of disease and in monitoring of response to therapy. PET is also likely to become used to allow more accurate planning of radiotherapy treatment. These applications are evolving rapidly as access to PET scanning becomes more widely available and as new tracers other than FDG are developed. Studies are necessary to evaluate the efficacy of these new indications and to define the role of PET in the patient pathway. These studies usually require large numbers of patients and are conducted as multi-centre trials across many sites.
PET in the Development of New Anti-Cancer Drugs
PET can be used in several ways to improve the efficiency of the time-consuming and expensive process of taking a new anti-cancer drug from the laboratory through to the clinic. New drugs can be labelled with a PET radionuclide to image their biodistribution and kinetics at a very early stage on a small number of volunteers - this may enable an unsuitable compound to be rejected at an early stage without having to go through large clinical trials. Well understood PET tracers, such as FDG, can then be used in later stage trials on large numbers of patients to determine how effective the drug is. PET is able to provide this information much more rapidly than currently used methods. Trials of new drugs are usually performed by or in collaboration with a pharmaceutical company. Early stage trials are usually more technically complex, requiring only a small number of subjects, and are performed at a small number of PET units. Later stage trials require large numbers of patients and are usually performed at a much larger number of sites.
PET in Translational Research
Because PET can be used to obtain information about tumour metabolism and the effects of new treatments in both animal models of disease and in human patients, it is proving useful in speeding up the 'translation' of studies from the laboratory into the clinic.
Development of PET Technology and Radiopharmaceuticals
PET scanner technology and the radiopharmaceuticals that are administered to the patient are themselves undergoing very rapid development at present. This work is performed both in academia and in industry. Current developments include, for example, the development of combined PET & MRI scanners and radiopharmaceuticals that can image tumour hypoxia and other properties that can be used to characterise tumours non-invasively.