PET Scans

PET scans, short for Positron Emission Tomography, can detect areas of cancer by obtaining images of the body’s cells as they work. First, you are injected with a substance made up of sugar and a small amount of radioactive material. Cancer cells tend to be more active than normal cells, and they absorb more of the radioactive sugar as a result. A special camera then scans the body to pick up any “highlighted” areas on a computer screen. This helps radiologists identify areas where cells are suspiciously active, which can indicate cancer. Once doctors know where to look, further evaluation can be done with other techniques. One example is a combined PET and CT Scan (known as PET/CT), available in some centers.

PET scans are not used to screen women for breast cancer. The test has only a limited ability to detect small tumors. PET scans can be useful for evaluating people after breast cancer has already been diagnosed, in a number of different ways:

• to determine whether the cancer has spread to the lymph nodes
• to determine whether the cancer has spread to other parts of the body, and if so, where (metastatic breast cancer)
• to assess whether metastatic breast cancer is responding to treatment

PET scans are available in only very few centers, and they are an expensive, sophisticated test that requires special expertise. Generally, they are used only if your doctor has reason to believe that the cancer may have spread beyond the breast. They also may be used if your doctor suspects recurrence of a previous breast cancer. PET scans can be helpful if other tests can’t tell for sure whether the cancer has spread beyond the breast or to other areas of the body.

To understand what PET scans show, compare these three PET scan images:

Normal PET scan

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PET scan showing abnormal lymph nodes

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PET in woman with breast cancer that has spread to bones

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Breastcancer.org would like to thank Dr. Amy Lansman at National Medical Imaging in Philadelphia for contributing these images.