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Multiple CT Scans and Nuclear Imaging May Increase Breast Cancer Risk

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A CT scan (also called a CAT scan, or computerized tomography scan) is an x-ray technique that gives doctors information about the body’s internal organs in two-dimensional slices. Right now, CT scans aren’t routinely used to look for breast cancer, but may be used to look at chest, spine, or abdominal problems, such as a herniated disc or lung disease.

Nuclear imaging makes images by detecting radiation from different parts of the body after a radioactive tracer material is injected or taken by mouth.

The main difference between nuclear imaging and CT scans is that nuclear imaging assesses how organs function and CT scans assess how organs look.

From 2000 to 2010, use of CT scans increased dramatically, and a study suggests that more CT scans may lead to a higher risk of breast cancer in women, especially young women who have repeat scans.

The study was presented at the 2012 Radiological Society of North America Annual Meeting. Read the abstract of “Breast Cancer Risks from Medical Imaging Including Computed Tomography (CT) and Nuclear Medicine among Females Enrolled in a Large Integrated Health Care System.”

The researchers reviewed the imaging test records of nearly 250,000 Chicago women. They found that in 2000, there were about 100 CT scans per thousand women and in 2010 there were 192 CT scans per 1,000 women – an annual increase of 6.8 percent.

In 2010, 46% of the CT scans exposed breast tissue to radiation.

Use of nuclear imaging went down over the same time period: in 2000 there were about 39 nuclear imaging scans per 1,000 women and in 2010 there were 27.5 nuclear imaging scans per 1,000 women. Still, 84% of the nuclear imaging studies done in 2010 exposed breast tissue to radiation.

The researchers estimated the amount of radiation the women were exposed to by collecting CT scan dose information from 1,656 women who had a CT scan that exposed breast tissue to radiation and putting that information into a computer program. They also analyzed the radiation exposure used in 5,507 nuclear imaging studies that exposed the breast to radiation.

The researchers then used a statistical risk model to estimate the women’s risk of breast cancer related to the imaging tests, based on a woman’s age when the tests were done, and compared it to their basic risk of developing breast cancer, which was based on information from the National Cancer Institute.

Young women who received several chest or cardiac CT scans had the greatest increase in breast cancer risk – about 20%.

While the results of this study sound scary, it’s important to keep several things in mind:

  • There are imaging tests that don’t use radiation, such as MRI (magnetic resonance imaging) and ultrasound.
  • The researchers estimated the radiation doses the women received from the diagnostic tests; in some cases, these estimates may not be perfectly accurate.
  • The benefits of x-ray diagnostic tests almost always outweigh any risks.
  • The study results are not based on real-life breast cancer cases, but on theoretical risk models, so the results are theoretical only.
  • The paper is preliminary; it was an abstract presented at a meeting and not published in a peer-reviewed journal.

If your doctor recommends diagnostic tests that involve x-rays, make sure you understand why the test is necessary and ask your doctor if the lowest possible radiation dose can be used. If you have a health problem that requires you to have multiple diagnostic tests, ask your doctor if any of these tests can be the type that doesn’t involve radiation. Together, you and your doctor can figure out a testing plan that makes the most sense for you and your unique situation.

For more information on diagnostic tests, visit the Breast Cancer Tests: Screening, Diagnosis, and Monitoring pages.

For more information on keeping your risk of breast cancer as low as it can be, visit the Lower Your Risk section.

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