Overdiagnosis in breast screening refers to a small number of cancers detected through a mammogram, which would not become life-threatening if left untreated.

What is overdiagnosis?

In relation to breast cancer, overdiagnosis refers to a small number of cancers (or groups of abnormal cells) detected through a mammogram, which would not progress to become life-threatening even if left untreated. Overdiagnosis does not mean an error or misdiagnosis.

As it is not currently possible to tell which cancers may go on to become life-threatening and which may not, it is difficult to estimate the level of overdiagnosis. However, most reliable research studies suggest overdiagnosis rates are low.

Overdiagnosis and Breast Screening

If you have concerns about overdiagnosis, it’s important to consider the following facts about breast screening:

  • Mammograms detect cancers before they can be seen or felt
  • Breast cancer treatment is most effective when cancers are still small
  • Early detection means treatment is less invasive and the chance of recovery is much higher
  • A mammogram is the best method of detecting cancer early in women aged 50 and over
  • As it is not currently possible to tell which breast cancers will go on to become life threatening, clinicians recommend that most breast cancers are treated
  • Since the introduction of the BreastScreen program in 1991, there has been a sharp decline in breast cancer-related deaths

If you’re aged 50-74 and have no symptoms of breast cancer, you should attend your free mammogram through BreastScreen NSW every two years. Remember, it only takes 20 minutes and could save your life!

Read more about the benefits of screening mammograms

Did you know?

The World Health Organisation estimates that for every 1-2 overdiagnosed cases, at least 1 death due to breast cancer was avoided by breast screening.

What if my breast screen shows I need an assessment?

If your screening mammogram shows the need for further tests, you will have the support of a specialist team of nurses, radiologists, surgeons, breast physicians and counsellors.

Your specialist assessment team will help you to understand your assessment results and assist you in making an informed choice about your treatment.

Read more about what happens if you need an assessment

Where can I get more information?

Use the links below to access more information on breast screening and overdiagnosis:

The World Health Organisation’s Position Paper on Mammography Screening

The World Health Organisation’s International Agency for Research on Cancer (IARC): Viewpoint on Breast Screening

Cancer Australia’s Position Statement on Overdiagnosis

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Recommended Resource

Download our brochure, BreastScreen and You, to find out more about mammogram screenings.

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