Oncology division - Nuclear medicine / imaging
PET scan in oncology: in which cancers and at which stages of the care pathway is it used?
A PET scan, often performed as a PET/CT, combines metabolic and anatomical information. In oncology, it can contribute to diagnosis, staging, detecting recurrence or assessing response, but its usefulness depends on the type of cancer, the tracer used and the clinical question.
Written by the Polycrabat Sevamed team · Published on · Updated on
In brief
- PET/CT is not a general cancer screening test.
- FDG is the most common tracer, but not all tumours take it up in the same way.
- The test must answer a precise indication and be interpreted together with imaging and pathology.
PET scan: an image of how tissues function
PET (positron emission tomography) is a nuclear medicine test. It uses a very small amount of radiotracer to observe certain biological functions. In oncology, the most widely used is FDG, a glucose analogue labelled with fluorine-18. Many cancer cells consume more glucose than the surrounding tissues, which can make them visible on PET. PET is often combined with CT (PET/CT) to superimpose metabolic information and anatomy.
Why is a PET scan not requested for all cancers?
Not all cancers take up FDG in the same way, and PET is not needed at every stage. Its usefulness depends on the tumour type and the clinical question: initial staging, looking for recurrence, assessing response to treatment, selecting an area to biopsy or treatment planning. Other tracers can be used for certain conditions.
EANM guidelines and those specific to each cancer specify in which situations the test adds value: an indication that is valid for one cancer cannot be extrapolated to another. After treatment, the timing of the test matters, because inflammation after surgery or radiotherapy can cause non-specific uptake.
A positive PET does not always mean cancer
Inflammation or infection can also take up FDG. Conversely, some small lesions or tumours with low uptake may be barely visible. The result must therefore be interpreted together with the clinical history, CT, MRI, pathology and other tests. A PET scan is not a biopsy.
High blood sugar can also disrupt the test. Interpretation by a nuclear medicine physician who knows the file is essential.
Radiation and precautions
PET involves exposure to radiation from the radiotracer and often from the associated CT. This exposure is justified when the expected information can change the management. Pregnant or breastfeeding women must always report this before the test.
Questions to ask
- What is the purpose of the PET scan in my case?
- Which radiotracer will be used?
- Do my diabetes or my medicines require special preparation?
- Will the result change the treatment strategy?
What Polycrabat Sevamed can coordinate
In a cancer care pathway, the coordination team can schedule the PET/CT when it is prescribed, obtain the report and add it to the file that will be discussed by the treating team.
Frequently asked questions
Does a PET scan detect all cancers?
No. Sensitivity depends on the tumour type, the tracer, the size of the lesion and the context.
Does uptake mean cancer?
No. Inflammation and infection can also take up certain tracers, particularly FDG.
Are a PET scan and a CT scan the same thing?
No. PET mainly provides functional/metabolic information; CT provides anatomical information. They are often combined in the same machine.
This content provides general medical information. It does not replace a consultation or a personalised decision by your care team. In case of serious or sudden symptoms, contact the emergency services in your country or a doctor without delay.
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How to prepare?
For an FDG PET/CT, the patient receives precise instructions on fasting, hydration, physical activity and, if diabetic, on managing blood sugar and medicines. Following these instructions directly affects image quality. RadiologyInfo recommends in particular reporting medicines, recent illnesses, pregnancy or breastfeeding and relevant allergies.
After the injection, a rest period allows the tracer to distribute. Image acquisition is painless and the patient must keep still. The total time spent in the department is longer than the time spent in the scanner ring.