Can You Still Have Cancer If a PET Scan Is Negative?
Positron emission tomography (PET) scans can detect cancer earlier than other imaging tests. But some types of cancer are harder to detect on a PET scan. In particular, they may miss cancers that don’t use a lot of glucose.
Positron emission tomography (PET) is a nuclear medicine imaging test. Using a special dye that contains radioactive tracers, PET scans help doctors diagnose a variety of diseases, including cancer, particularly in the early stages.
PET imaging can also help determine how well cancer treatment is working.
It’s an effective way to find cancer, but a negative PET scan doesn’t always mean there’s no cancer.
There are some conditions that can lead to a false-negative or a false-positive result. That’s why it’s often performed in combination with computed tomography (CT) scans, magnetic resonance imaging (MRIs), and other diagnostic tests.
Let’s take a closer look at PET scans for cancer and what a negative result may mean.
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PET scans are effective imaging tests. They can detect abnormal activity in the body and often find cancerous tumors earlier than other imaging tests can.
But the degree of accuracy varies with the type of cancer and how it’s combined with other tests.
The most commonly used radioactive substance in PET imaging is F-FDG, a type of glucose. Once this solution is injected into a vein, it makes parts of your body that use a lot of glucose light up on the scan. Many types of cancer cells use a lot of glucose, so they show up as hot spots on the scan.
But F-FDG isn’t cancer-specific. So, PET scans may reveal hot spots that aren’t necessarily related to cancer.
False positives can happen due to conditions such as:
- bacterial and fungal infections
- sarcoidosis
- radiation pneumonitis
- post-operative surgical conditions
Blood sugar and insulin levels can also affect results. So, you can get a false-positive result if you have diabetes or if you ate something within a few hours of the test.
For these reasons, PET scans are often performed along with other tests, such as CT scans or MRIs. It takes a specially trained radiologist or nuclear medicine specialist to evaluate and interpret the results.
Other tracers may be used to look for specific types of cancer. For example, prostate-specific membrane antigen (PSMA) can help detect prostate cancer.
Research published in 2020 suggests that in men with prostate cancer, PSMA PET-CT is more accurate than a CT combined with a bone scan.
