Breast PET scan

Definition

A breast positron emission tomography (PET) scan is an imaging test that uses a radioactive substance (called a tracer) to look for breast cancer. This tracer can help identify areas of cancer that an MRI or CT scan may miss.

See also: PET scan

Alternative Names

Breast positron emission tomography; PET - breast; PET - tumor imaging - breast

How the test is performed

The health care provider will inject a small amount of a radioactive material into one of your veins, usually on the inside of the elbow. The substance travels through the blood. It is more likely to collect in cancer tissue.

You will be asked to wait nearby as the radioactive substance is absorbed by your body. This usually takes about 1 hour.

Then, you will lie down on a table that slides into a tunnel-shaped hole in the center of the PET scanner.

The PET machine detects energy given off by the radioactive substance and changes it into pictures. The images are sent to a computer, where they are displayed on a monitor for the health care provider to see.

You must lie still during the PET scan so that the machine can produce clear images of your lungs.

Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT.

The test takes about 90 minutes.

How to prepare for the test

You must sign a consent form before having this test. You will be told not to eat anything for 4 - 6 hours before the PET scan, although you will be able to drink water.

Tell your doctor if you are pregnant or think you might be pregnant.

Also tell your doctor about any prescription and over-the-counter medicines that you are taking, because they may interfere with the test.

Be sure to mention if you have any allergies, or if you’ve had any recent imaging studies using injected dye (contrast).

People with diabetes who take insulin injections will need special preparation. Call the PET scan office the day before the study for instructions.

During the test, you may need to wear a hospital gown. Take off any jewelry, dentures, and other metal objects because they could affect the scan results.

How the test will feel

You will feel a sharp prick when the needle with the radioactive substance is inserted into your vein. You shouldn’t feel anything during the actual PET scan.

Why the test is performed

A PET scan is most often used when other tests, such as MRI scan or CT scan, do not provide enough information.

A breast PET scan is used only after a woman has been diagnosed with breast cancer. It is done to see if the cancer has spread to other parts of the body such as lymph nodes, liver, lung or bones.

If you have breast cancer, your doctor may order this scan:

• Soon after your diagnosis to see if the cancer has spread
• After treatment if there is concern that the cancer has come back
• During treatment to see if the cancer is responding to treatment

A PET scan is not used to screen for, or diagnose, breast cancer.

Normal Values

A normal result means there are no areas outside the breast in which the radiotracer has abnormally collected. This result most likely means the breast cancer has not spread to other parts of the body.

Very small areas of breast cancer may not show up on a PET scan.

What abnormal results mean

Abnormal results may mean that breast cancer that has spread.

What the risks are

The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation doesn’t last for very long in your body.

However, women who are pregnant or are breastfeeding should let their doctor know before having this test. Infants and fetuses are more sensitive to the effects of radiation because their organs are still growing.

Before receving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

It is possible, although very unlikely, to have an allergic reaction to the radioactive tracer. Let your doctor know if you have ever had an allergic reaction to injected contrast dye. Some people have pain, redness, or swelling at the injection site.

Special considerations

It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes.

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References

Podoloff DA, Ball DW, Ben-Josef E, et al. NCCN task force: clinical utility of PET in a variety of tumor types. J Natl Compr Canc Netw. 2009 Jun 7. Suppl 2:S1-26. Review.

Hackney D. Radiologic imaging procedures. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 419.