For many cancers, especially those that are likely to spread throughout the body, it is important to find out if the cancer has spread and where it has spread. This is called staging. Knowing the stage helps the doctor decide what kind of treatment is best and can help understand a patient's prognosis when the cancer is first diagnosed. Breast cancer is divided into stage 0 (zero), which is called ductal carcinoma in situ (DCIS), and stages I through IV (one through four). Find more detailed staging information for breast cancer .
Staging is based on the patient's symptoms, a careful physical examination, size of the breast tumor and any nearby lymph nodes, and some common blood tests . If the cancer is thought to have spread, doctors can use imaging tests (tests that create pictures of the inside of the body) to help find out if or where a cancer has spread. For breast cancer, these can include computed tomography (CT or CAT) scans  and positron emission tomography (PET) scans , as well as bone scans to find out if the cancer has spread to the bone.
ASCO recommends that the following imaging tests are not used for staging DCIS or stage I or II breast cancers where there are no signs that the disease has spread:
- CT scan
- PET scan
- Bone scan
DCIS and stage I or II breast cancers have a low risk of having spread outside of the breast and nearby lymph nodes when diagnosed. Research on these tests has shown that they are often falsely positive (the results say there is cancer when there is not), expose people to unnecessary radiation, and do not help lengthen lives.
What this means for patients
CT, PET, and bone scans can be helpful tools in the right situations, such as for people whose symptoms, physical examination findings, size of the breast tumor or lymph nodes, or blood test results suggest later-stage breast cancer (stages III and IV). The tests can show abnormal-looking areas in parts of the body that cannot ordinarily be seen or felt. It's important to remember that not all abnormal-looking areas in the body are cancerous. However, anytime there is something abnormal on these tests, more tests are needed to find out if it is cancerous. For people with early-stage breast cancer that is unlikely to have spread, having these tests can often add extra procedures, additional exposure to radiation, more worry, and higher costs without improving their return to normal life.
Questions to ask your doctor
- What stage of breast cancer do I have?
- How is the stage determined?
- What tests do I need to determine the stage?
- Do I need imaging tests of parts of the body other than my breast? Why or why not?
- What other information would these tests provide that could help determine my treatment options?
- What is the cost of each test?
For More Information
Consumer Reports: Imaging and Tumor Marker Tests for Breast Cancer  (Topics 3 and 4; PDF)