All screening tests, including mammography, have benefits and limitations. Knowing what they are may help you make an informed decision about what is right for you.

Benefits

• The earlier detection of early stage breast cancers: if breast cancers are detected when they are small and have not spread, most patients can be treated successfully.

• Better treatment options:  if results indicate early stage breast cancer, in most cases, this leads to more treatment options with less invasive forms of treatment (e.g. lumpectomy rather than mastectomy). 

• Reduced death and disability from breast cancer:  in most cases, the earlier detection and timely treatment of breast cancer reduces the risk of death or long-term disability. 

• Access to the highest quality screening when you have a mammogram at your provincial or territorial organized breast cancer screening program or an accredited clinic. These screening clinics have highly trained staff who specialize in breast cancer detection. They also meet national standards for radiologist and medical radiation technologist qualifications, equipment, image quality, radiation dose, quality control and quality assurance. 

• Feeling empowered by participating in screening and taking action for your breast health. Screening is an important part of preventive health care and is a concrete action you can take for your breast health.  

Limitations

• No screening test is 100 per cent perfect.

• Some test results show signs of cancer that are ruled out when further testing is done (this is called a false positive). About one in ten women may be called back for more testing after their mammogram. These tests may be taken with ultrasound or MRI and sometimes a biopsy is required. Do not be alarmed if you are called back. Most women who require additional testing will not have breast cancer.

• Other test results miss breast cancer (this is called a false negative). This type of screening result is rare. However, it may lead to a false sense of security and a delay in diagnosis and treatment. Regular screening at specific time intervals is the best way to overcome this limitation.

• Some breast cancers that are found by mammography would never become a health problem in the woman’s lifetime (e.g. some cancers grow very slowly).

• Mammography cannot detect which cancers will not threaten the woman’s health from those that will be harmful and must be treated. So, all signs of breast cancer are treated as harmful. This limitation is known as over-diagnosis.

• Mammograms use X-ray radiation.

• Modern mammography equipment used today requires very small doses of radiation. Medical studies confirm that the risk of harm from this radiation exposure is very low.

• X-ray technologists at the provincial and territorial organized screening programs have been trained to know how to position the breasts to reduce the level of radiation exposure.

• Research shows that the benefits of the earlier detection of breast cancer by mammography outweigh the risk of low-dose radiation exposure.

To help you make an informed decision about what is right for you, the Canadian Breast Cancer Foundation encourages you to learn about your breast health, breast cancer risk, ways to reduce your risk, and the benefits and limitations of breast cancer screening. To inform your decisions, we also encourage you to consider speaking with a health care provider. 

More Information:

When to get a mammogram

Where to go for a mammogram

What to expect when you go for a mammogram

Breast cancer risk factors

Reducing your risk of breast cancer 

Sources:

Canadian Breast Cancer Foundation. (2010).  Earlier Detection and Diagnosis of Breast Cancer. Recommendations and Scientific Review from It’s About Time! A Consensus Conference. Toronto, ON: Canadian Breast Cancer Foundation.

Health Canada.  It’s Your Health: Mammography.  Accessed July 31, 2011.

Public Health Agency of Canada.  Information on mammography for women aged 40 and older. Accessed July 31, 2011.