It's Your Health

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The Issue

In certain situations, women are advised to have breast X-rays, known as mammograms, to detect breast cancers at their earliest possible stage of development. Some women may have questions about the benefits of having a mammogram and the potential effects of being exposed to radiation during the procedure.


Breast cancer is one of the leading causes of cancer-related deaths in Canadian women. In 2006, there will be an estimated 21,600 new cases in women aged 20+ and 5,300 deaths from breast cancer in Canada. About 11% of Canadian women (one in nine) will get breast cancer at some point in their lives. The risk of developing breast cancer increases as women get older.

When breast cancer is detected early through a mammogram, there are better treatment options and a greater chance for a successful recovery.


Mammography is an imaging technique that uses X-rays to provide a picture of the internal structure of the breast. Mammograms can be done for diagnostic or screening purposes.

Diagnostic: Your doctor may recommend a diagnostic mammogram if you have a symptom that needs to be investigated, such as a lump in your breast.

Screening: This type of mammogram looks for signs that breast cancer may be developing, even though you have no symptoms.

Mammography as a Screening Tool

The X-ray images used in mammography can show abnormal growths or changes in breast tissue before they can be felt. In addition to detecting breast cancer in its early stages, mammography is also an effective way to determine that women do not have breast cancer. This makes mammography the best tool available to screen for breast cancer in women.

Mammography is the only technique proven to be safe and effective in screening for breast cancer, and mammography equipment is the only imaging technique licensed by Health Canada for breast cancer screening.

If a suspicious lesion shows up on a mammogram, other techniques - such as ultrasound, biopsy magnetic resonance imaging (MRI) and laser scanning - may be used for further investigation. However, none of these other techniques is recommended for screening purposes at this time.

New technologies, such as thermal scanning (thermography), are being evaluated to see if they are safe and effective. Claims that thermography is useful in diagnosing breast cancer have not been proven, and thermography equipment has not been licensed for breast cancer screening in Canada.

When to have a Mammogram

Core Screening

Many doctors and screening programs recommend screening mammograms every two years for women who are 50 to 69 years old. Studies show that regular screening mammograms can reduce deaths from breast cancer by as much as one-third for women in this age group.

There have been studies about whether regular screening mammograms would also be beneficial for women outside the 50 to 69 age-range. To date, the evidence is not conclusive.

Other Situations

If you have a family history of breast cancer (mother, sister, daughter), or have had a breast biopsy that showed abnormal cells, this may indicate an increased susceptibility to breast cancer. Your doctor will recommend mammograms at intervals based on your particular needs even if you are outside the 50-69 age range.

Also, your doctor will recommend a mammogram if there is reason to suspect that you may have breast cancer, for example, if you or your doctor discover a lump in your breast.

What To Expect

During a mammogram, the X-ray technologist uses special equipment to compress your breast tissue to get as clear a picture as possible. This may cause some temporary discomfort, but it is usually not severe.

A radiologist will assess the X-ray images and forward the results to your doctor. Some breast cancer screening programs may contact you directly with the results.

Most screening mammograms come back with normal results. If your mammogram shows there are lumps in your breast, but they are not cancerous, it is important to monitor the lumps so if there is a change in the breast tissue you can see a doctor immediately. If there is a cause for concern, your doctor will recommend next steps, including more tests.

Mammography and Radiation

The risk of getting cancer from a mammogram is extremely low. An X-ray machine is used for the mammogram and the radiation dose with a mammogram is quite low. Your body can usually repair the few cells that might be damaged by the X-rays. The benefit of early diagnosis and treatment for breast cancer far outweighs the risk of the small amount of radiation received during a mammogram.

Minimizing Your Risk

There is plenty of evidence that early detection and treatment of breast cancer saves lives.
All women should talk to their doctor about the risk of getting breast cancer. This is especially important for women with a family history of early onset breast cancer; if this is your situation, you may benefit from having mammograms, as well as genetic screening.

Women who are 50 to 69 years of age should have screening mammograms every two years. Ask your doctor about this or contact a breast cancer screening program in your province or territory. (See the Need More Info? section for more on this.)

Remember, mammography is the only imaging technique proven to be safe and effective for breast cancer screening. Do not take a chance with your health by relying on unproven, alternative technologies to screen for breast cancer.

The Government of Canada's Role

Health Canada regulates the importation and sale of medical devices and radiation emitting devices in Canada, through the Food and Drugs Act, the Radiation Emitting Devices Act, and the Medical Devices Regulations. These Acts and Regulations assure the safety, effectiveness and quality of medical devices, including mammography equipment, when they are used for their licensed purpose. Health Canada also provides guidance to mammography facilities through the Canadian Mammography Quality Guidelines.

In addition, the Public Health Agency of Canada works through the National Committee of the Canadian Breast Cancer Screening Initiative to support the development of quality, organized breast cancer screening programs in Canada The National Committee monitors and assesses the performance of screening in Canada every two years. It also encourages the use of best practices in breast cancer screening.

Need More Info?

For more information, contact:

Consumer and Clinical Radiation Protection Bureau, Health Canada
775 Brookfield Road
Ottawa, ON K1A 1C1
Telephone: 613-954-6699


Medical Devices Bureau, Health Canada
Room 1605, Statistics Canada Main Building
Tunney's Pasture
Ottawa, ON K1A 0L2
Telephone: 613-957-4786


Screening and Early Detection Section, Public Health Agency of Canada
120 Colonnade Road
Ottawa, ON K1A 1B4
Telephone: 613-952-6143

Also, see the following Web sites:

For information about breast cancer screening programs, contact your provincial health ministry or call the Canadian Cancer Society information line at 1-888-939-3333 (toll-free in Canada), or see the brochure.

To find an accredited breast cancer screening facility, talk to your doctor or search the online database compiled by the Canadian Association of Radiologists.

Also, see the It's Your Health article on Breast Cancer.

For additional articles on health and safety issues go to the It's Your Health Web site. You can also call toll free at 1-866-225-0709 or TTY at 1-800-465-7735*.

Updated: January 2007
Original: November 2001
© Her Majesty the Queen in Right of Canada, represented by the Minister of Health, 2007

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