Information on Mammography for Women Aged 40 and Older

A Decision Aid for Breast Cancer Screening in Canada

For readers interested in the full version of this booklet, the document is available for downloading or viewing:

PDF Version 
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Table of Content

• Introduction:
  • What is a Decision Aid
• Breast Cancer Facts:
  • How common is breast cancer in Canada?
  • What are the risk factors?
  • What protects you against breast cancer?
• Breast Cancer Screening
  • What is breast cancer screening?
  • What is a mammogram?
  • Are mammograms safe?
  • What might happen if you participate in breast cancer screening mammography?
  • What are the possible benefits and harms of screening mammograms?
• Having a regular screening mammogram
  • Women aged 40-49 years
  • Women aged 50-69 years
  • Women aged 70-79 years
• Help with your decision
  • Personal Worksheet
  • Where else can you get help with your decision?

What is a decision aid?

A decision aid is used to increase your knowledge so that you can make better informed decisions about your own health care.

This is a decision aid. It is for women aged 40 and older who:

• do not have breast cancer;
• do not have any breast problems; and
• have not been told that they are at high risk of breast cancer.

Its goal is to provide you with information on breast cancer screening using mammography and to help you decide whether to be part of breast cancer screening or not. In this decision aid, you will learn about breast cancer risks, mammography’s benefits and harms, and how to decide about screening mammography based on your age group (40-49, 50-69, 70-79). Refer to age specific sections to help you decide about screening!

There is a worksheet which we suggest you complete to help you make your decision about breast cancer screening using mammograms. You may wish to discuss it with your health care provider.

How common is breast cancer in Canada?

Breast cancer is one of the most common forms of cancer in women. Each year, more than 22,000 women develop breast cancer in Canada and more than 5,000 women die of the disease. Based on current rates, one in nine women in Canada is expected to develop breast cancer during her lifetime.

The risk of getting breast cancer goes up as women get older. The risk of developing breast cancer in the next 10 years is as follows:

• 13 out of 1,000 women in their 40s
• 23 out of 1,000 women in their 50s
• 29 out of 1,000 women in their 60s
• 31 out of 1,000 women in their 70s

Since 1999, the rate of new cases of breast cancer has stabilized, and death rates have steadily declined.

What are the risk factors for breast cancer?

"Please note: the reference numbers in the printed Decision Aid contain some errors. The reference numbers below in the text and the PDF have been corrected."

Risk factors are conditions that may increase your chance of developing breast cancer. Some risk factors are major, while others are minor.^1-4 It is important to understand that most women will have some of these risk factors.

• A major risk is one that puts you at least twice the risk of breast cancer compared to someone without that risk factor.
• A minor risk is one that put you at less than twice the risk.

Most women will have some of these risk factors

Major risk factors for breast cancer

Minor risk factors for breast cancer

Being aged 50 or older.1-5 Dense breast tissue as shown by a mammogram. Breast density is often lower as women age and after menopause.1-3, 6-9 Having a previous breast tissue sample (biopsy) that showed cells that look abnormal (atypical hyperplasia). 1-4, 10 A mother or sister with breast cancer especially if they learned they had breast cancer before age 50.1-5, 11-13 If more than one immediate family member had breast cancer12, or if your family has a history of ovarian cancer.11 Some families may have mutation of a breast cancer gene (a permanent change in the DNA of either of the genes known as BRCA1 or BRCA2).1, 3-4, 14-15 Repeated radiation to the chest due to treatment of a disease (such as Hodgkin’s). The risk is highest if you were exposed to the radiation between ages 13 to 30. 1-4

Not having any children or being more than 30 years old when a first child was born.1-2, 4, 13, 16 Starting your monthly periods (menstruation) before age 12.1-2, 4-5, 13 Late menopause (after age 55).1-3, 13 Current use of hormone replacement therapy that totals 5 years or more.1-4, 17-21 Current use of the birth control pills and for 10 years after you stop taking them.1-2, 4, 22-24 Overweight after menopause.1, 3, 25-27 Having more than one drink of alcohol per day. 1-3, 19, 28-31

If you are not sure about whether you have some of these risk factors, talk to your health care provider.

Although more research is necessary before conclusions can be made, some scientific studies show other risk factors that may be linked to a higher risk of breast cancer including: ^31-37

• a diet high in fat,
• smoking, or
• being exposed to second-hand smoke.

You may want to check off all your major and minor risk factors so that you can refer back to them later.

• How many major risk factors do you have?
• How many minor risk factors do you have?

To get a better sense of your breast cancer risk, you can ask your health care provider or use the Breast Cancer Risk Calculator available on the Public Health Agency of Canada website. This tool uses seven risk factors to predict the risk of breast cancer.

What protects you against breast cancer?

Be aware of the risk factors that you can change. These include your weight, diet, and whether you smoke or drink alcohol. Studies show that women can reduce their risk by being physically active.^{18, 38-39} Women who have given birth to more children and women who breastfed have lower breast cancer risk.^{4, 13, 18, 40-41}

What is breast cancer screening?

Breast cancer screening is an attempt to find cancer even when there may not be any symptoms. The goal is to find breast cancer early, when it is small and less likely to have spread to other parts of the body. This reduces a woman’s chance of dying from the disease. The most common method of breast cancer screening is a mammogram.

What is a mammogram?

A mammogram is a medical test that uses x-rays to take pictures of the internal structure of the breast. The testing is also known as “mammography.” Mammograms are done for two reasons:

Screening: When women participate on a routine basis to have mammograms done to find breast cancer at an early stage. This type of mammogram looks for signs that breast cancer may be developing, even though no symptoms are there.

Diagnostic: This is typically done to check for breast cancer after a lump or any other sign/symptom has been found such as pain, skin thickening, nipple discharge, or a change in breast size or shape. It may also be used as a second test if a screening mammogram finds something that is not normal.

Here’s how a screening mammogram works:

• You will be seated or standing in front of a machine used only for mammograms.
• The x-ray technologist will place your breast onto a plastic plate on the machine. As a second plastic plate is lowered onto the breast, pressure will even out the breast tissue. This allows the machine to get as clear a picture as possible. The tolerance to pressure on the breast varies among women.⁴²
• A special low-dose x-ray is then used to look for breast patterns or lumps that are not normal. These may be too small for you or your health care provider to find by feeling your breast.
• The same procedure then occurs with the other breast.
• High quality mammogram finds some breast cancers when they are very small—2 to 4 years before they would be felt.⁴³

Are mammograms safe?

Mammograms involve exposure to x-rays and x-ray radiation has been found to cause cancer. The amount of radiation you receive during one screening mammogram will be based on:

• the amount of fat in your breast tissue (density); and
• the number of images taken.

Your total exposure to radiation from screening mammograms will depend on the number of mammograms you have had. X-ray technologists are experts in breast positioning and know how to reduce the amount of radiation you receive. The amount of radiation that you get from a screening mammogram is almost the same as the amount you would receive over 3 months from your usual surroundings (e.g. sun, rocks, soil, buildings, air and food).⁴⁴ Studies show that the risk of a new cancer starting due to radiation to the breast from breast screening mammography is extremely low.^45-48 The benefits of early diagnosis and treatment of breast cancer far outweigh the risk of being exposed to the small amount of radiation from a screening mammogram.

What might happen if you participate in breast cancer screening mammography?

You may experience one of the following outcomes as shown in Figure 1 below.

Screening and Follow-up

Cancer may occur in between screening visits.

Figure 1 - This flow charts shows the screening outcomes and follow-up if a woman happens to participate in the breast cancer screening mammography. A woman undergoing mammography would show two results a) No cancer found (normal mammogram) b) Some abnormality found requiring further tests. On further testing, some women will have cancer and some will not (false alarms). However, in some women, cancer may occur in between screening visits.

What are the possible benefits and harms of screening mammograms?

The possible benefits and harms linked to breast screening mammograms are listed in the table below. Consider each statement on its own to determine how important each one is to you.

Possible Benefits	Possible Harms
Peace of mind You may feel less worried when you know that you do not have cancer on your screening mammogram.	Cancer may not be found Your mammogram may show no signs of an abnormality even though breast cancer is present.
Catching cancer at an early stage and simpler treatment If your mammogram finds something abnormal, you will be carefully monitored and/or treated. In Canada, more than 97% of breast cancers found by organized screening programs are at an early stage. If your cancer is at an early stage, you may have simpler surgery and less need for chemotherapy.	Extra tests and worry from false alarms Some women will have a false alarm because something abnormal is found on mammogram. But after more tests (such as another mammogram, an ultrasound or perhaps a biopsy), no cancer is found. This may take 4 to 6 weeks, causing worry in women. Sometimes, the worry lasts long after the test results are known.
Reduced chance of dying from breast cancer The purpose of breast screening mammograms is to find breast cancer early. This reduces your chance of dying from breast cancer due to early diagnosis and simpler treatment.	No improvement to your length and/or quality of life and unnecessary diagnosis Even though your screening mammogram found breast cancer, your quality of life or the number of years you live may not change. Some breast cancers found by screening would otherwise cause no problems because women would die of something else first. These breast cancers could be slow growing cancers. So, if women with these cancers had not had screening, they might never have known they had cancer and would not have had treatment.

Having a regular screening mammogram

In Canada, experts agree that the benefits of screening mammograms outweigh the harms for women aged 50 to 69. For younger and older women, the balance of benefits and harms is not so clear. Talk to your health care provider about your breast cancer risk and decide what is right for you.

Health officials recommend that women aged 50-69 years have breast screening mammograms once every two years. Note that women aged 40-49 years who choose to have a screening mammogram usually have it done once a year.

The following section discusses the results that Canadian women (of different age groups) can expect if they decide to have breast screening mammograms. The numbers presented are estimates from a mathematical model of breast cancer screening, based on the recent data (2000–2004) from the Canadian Breast Cancer Screening Database (CBCSD).

Review the specific section that tells you about the screening outcomes for your age group!

The next section will help you to understand how likely you are to experience a benefit or harm from mammography.

Women aged 40-49 years

If you decide to have screening mammograms, what are your chances of experiencing the screening outcomes (as shown in Figure 1)?

Imagine 1000 women aged 40 years starting screening and being screened once every year over 10 years. What would happen? We found that these women will typically experience the following outcomes:

• 981 women will not have breast cancer.
• 451 women will have normal results.
• 549 women will have abnormal results at some point during 10 years.
  • 533 of the abnormal results will be false alarms, which turn out to be normal after further testing.
• 16 women will have breast cancer detected by screening.
• 3 women will develop breast cancer in between screening visits

Since screening aims to reduce the risk from dying from breast cancer we can look at the estimated number of woman that needs to be screened to prevent one death.

If we screen 1,000 women aged 40-49 years once a year for a period of 10 years:

• 1 death from breast cancer will be prevented.
• 12 women will die from some cause other than breast cancer.
• 2 women will die of breast cancer despite breast cancer screening.

How will this affect my chance of dying from breast cancer?

Figure 2 - The bar chart shows that death from breast cancer is uncommon. Screening prevents one death from breast cancer among 1,000 women screened each year between ages 40 and 49.

Women aged 50-69 years

If you decide to have screening mammograms, what are your chances of experiencing the screening outcomes (as shown in Figure 1)?

Imagine 1000 women aged 50 years starting screening and being screened once every two years for a period of 20 years. What would happen? We found that these women will typically experience the following outcomes:

• 940 women will not have breast cancer.
• 426 women will have normal results.
• 574 women will have abnormal results at some point during 20 years.
  • 529 of the abnormal results will be false alarms, which turn out to be normal after further testing.
• 45 women will have breast cancer detected by screening.
• 15 women will develop breast cancer in between screening visits.

Since screening aims to reduce the risk from dying from breast cancer we can look at the estimated number of woman that needs to be screened to prevent one death.

If we screen 1,000 women aged 50-69 years once every two years for a period of 20 years:

• 5 deaths from breast cancer will be prevented.
• 107 women will die from some cause other than breast cancer.
• 7 women will die of breast cancer despite breast cancer screening

How will this affect my chance of dying from breast cancer?

Figure 3 - The bar chart shows that screening prevents 5 breast cancer deaths among 1,000 women screened once every two years between ages 50 and 69.

Across Canada, health officials recommend that women aged 50 to 69 have a breast screening mammogram once every two years.

Women aged 70-79 years

If you decide to participate in the screening program or you are already in the screening program, what are your chances of experiencing the screening outcomes (as shown in Figure 1)?

Imagine 1000 women aged 70 years undergoing screening once every two years for a period of 10 years. What would happen? We found that these women will typically experience the following outcomes:

• 961 women will not have breast cancer
• 756 women will have normal results.
• 244 women will have abnormal results at some point during 10 years.
  • 213 of the abnormal results will be false alarms, which turn out to be normal after further testing.
• 31 women will have breast cancer detected by screening.
• 8 women will develop breast cancer in between screening visits.

Since screening aims to reduce the risk from dying from breast cancer we can look at the estimated number of woman that needs to be screened to prevent one death.

If we screen 1,000 women aged 70-79 years once every two years for a period of 10 years:

• 3 deaths from breast cancer will be prevented.
• 208 women will die from some cause other than breast cancer.
• 7 women will die of breast cancer despite breast cancer screening

How will this affect my chance of dying from breast cancer?

Figure 4 - The bar chart shows that screening prevents 3 breast cancer deaths among 1,000 women screened once every two years between ages 70 and 79.

Think about your options for breast screening

1. You can start having mammograms.
2. You can keep on having mammograms.
3. You can stop having mammograms.

Help with your decision – What do you do next?

Print and fill out the Personal Worksheet! PDF Version (This link opens in a new browser window) (32 Pages - 862 kb)

This worksheet aims to help you consider the key points as you decide about screening mammograms. It is not intended to tell you exactly what to do. It is simply to help you collect your thoughts. Please complete the worksheet and if you feel that you need to discuss this further, then talk to your health care provider.

The worksheet will help organize your thoughts by going through the following

STEP 1: How do you rate your risk of breast cancer and overall health?

How do you feel about your risk of breast cancer?

• Very worried
• A little worried
• Not worried

How do you rate your overall health?

• I am in good health
• My health is okay
• I am in poor health

STEP 2: What are you doing for breast health?

Do you have a breast exam with a health professional as part of your regular health check-up?

• Yes
• No

Have you had a screening mammogram within the last 2 years?

• Yes
• No

Do you limit alcohol to 1 drink or less each day?

• Yes
• No

Do you have a healthy body weight?

• Yes
• No

Do you do moderate exercise at least 4 times a week (Examples of moderate exercise are brisk walking or swimming for 30 to 60 minutes, 4 times a week)?

• Yes
• No

STEP 3: How important are the possible benefits and harms of having mammograms?

• Look at each of the benefits and harms in the table below.
• Add any other benefits and harms important to you.
• Decide how important each is by checking them off (√)

Possible Benefits		Possible Harms
Peace of mind		Cancer may not be found
Catching cancer at an early stage and simpler treatment		Extra tests and worry from false alarms
Reduced chance of dying from breast cancer		No improvement in length or quality of life and unnecessary diagnosis
Other Benefits		Other Harms

STEP 4: How do you feel about screening mammograms?

Choose the statement that reflects how you feel:

• I want to start or continue mammograms
• Not sure
• I do not want to start or continue mammograms

STEP 5: Who should decide whether or not you start having or continue to have mammograms?

• I should, after thinking about the advice I received from my health care provider.
• I want to share the decision-making with my health care provider.
• I want my health care provider to decide.
• I am not sure.

STEP 6: What questions do you have about whether or not to start having or to continue to have mammograms?

STEP 7: You may wish to share this worksheet with your health care provider.

Where else can you get help with your decision?

Here is a list of resources that may help you decide what to do:

• The worksheet provides you with the key points you need think about as you decide whether screening mammograms are right for you or not.
• Your health care provider.
• The Public Health - Decision Aids website for:
  • a PDF version of this booklet.
  • the brochure Breast Cancer and Your Risk. This includes a list of breast cancer risk factors and tips on how to assess your risk.
  • the document Organized Breast Cancer Screening Programs in Canada: Report on Program Performance in 2003 and 2004. This includes more information on breast cancer screening mammography programs in Canada.
• Other Canadian breast cancer websites:
  • Canadian Cancer Society (External link)or call the Cancer Information Service at 1-888-939-3333.
  • Canadian Breast Cancer Network (External link)
  • Canadian Breast Cancer Foundation (External link)
  • Canadian Partnership Against Cancer (External link)

To find an organized breast cancer screening program in your area, use the telephone numbers listed below. If an organized program is not available in your region, your health care provider will refer you to your nearest radiology service.

• Alberta
  1-800-667-0604
• British Columbia
  1-800-663-9203
• Manitoba
  1-800-903-9290
• New Brunswick
  Call your Regional Health Authority
• Newfoundland
  1-800-414-3443
• Northwest Territories
  1-867-873-0452
• Nova Scotia
  1-800-565-0548
• Nunavut
  Call your health care provider or Health Centre
• Ontario
  1-800-668-9304
• Prince Edward Island
  1-888-858-2915
• Quebec
  Call your heath care provider or Info-Santé
• Saskatchewan
  1-800-667-0017
• Yukon
  1-867-393-8738

To obtain printed copies please send your requests to publications@hc-sc.gc.ca or call our toll free number 1-866-225-0709 (TTY: 1 800 267-1245) and ask for Publications.

To share your feedback on the decision aid, please contact the Public Health Agency of Canada by email at PHAC_Web_Mail@phac-aspc.gc.ca.

References

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Technical Notes

This information is for readers who want to know how the numbers were chosen and where they came from. You do not need to read this before you decide whether to start or continue having mammograms.

The following are the data sources, assumptions and calculations used in this decision aid. These are the best estimates based on available data. Data are subject to review as more information becomes available.

1. Outcomes of Screening with Mammography

   A mathematical model for the potential benefits and harms of breast cancer screening in Canada was developed by the Evidence and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, at the Public Health Agency of Canada using a Markov design and TreeAge computer software.

   The model investigated long term outcomes of regular mammography screening for three age groups: 40 to 49 years, 50 to 69 years and 70 to 79 years.

   Data sources were as follows:

   1. Public Health Agency of Canada: 5-year (2000–2004) data from the Canadian Breast Cancer Screening Database ( CBCSD ) including the number of participants, total number of screening mammograms, screening results (normal/abnormal), diagnostic tests, breast cancer staging, and interval breast cancers. Annual data for the full screening period, for each group extracted for 10-year age groups (40 to 49, 50 to 59, 60 to 69, and 70 to 79 years). The CBCSD is a collection of data shared with the Public Health Agency of Canada by provinces and territories with organized screening programs.
   2. Statistics Canada: all cause mortality, breast cancer incidence (new cases) and mortality, and Canadian population counts.
   3. Canadian Community Health Survey: reported overall participation in breast cancer mammography screening, including both organized and fee-for-service screening.

   Three scenarios were modeled:

   • 40 to 49 years: 1,000 40-year old women participating in 10 annual screens vs. not screening at all;
   • 50 to 69 years: 1,000 50-year old women participating in 10 biennial screens vs. not screening at all; and
   • 70 to 79 years: 1,000 70-year old women following recommended screening between 50 and 69 years and continuing with an additional 5 biennial screens, vs. not continuing to screen into their 70s.

   In order to calculate potential screening mammography risks and benefits in Canada, the following assumptions were used to produce the model:

   • 100% re-screen compliance. Compliance was defined as having a re-screen ≤15 months for 40 to 49 years; ≤30 months for women aged 50 years and older;
   • Probabilities all constant over time;
   • Detection rate same for both organized screens and fee-for-service screens; and
   • People who have been recalled in the past have the same chance of being recalled as those who were not originally recalled.

   Screening outcomes were modeled using full screening period data (10 to 20 years) from the CBCSD and defined as:

   Normal results: calculated by subtracting the number of women who experience an abnormal result from the total cohort (1,000 women).

   False negatives: the estimated number of women in the cohort given an initial normal result, but who are diagnosed with an interval breast cancer <12 months after their last screen and before their next scheduled screen.

   Abnormal results: the estimated number of the women in the cohort who experience an abnormal result at least once over the full screening period.

   Further imaging only: the estimated number of women in the cohort with an abnormal result who are recalled for at least one diagnostic mammogram or ultrasound over the full screening period with or without surgical consult or primary care referral, yet are not recalled for biopsy.

   Other tests and primary care: the estimated number of women in the cohort with an abnormal result who are recalled for a surgical consult, clinical breast exam, or primary care, yet are not recalled for further imaging or biopsy.

   Imaging and biopsy: the estimated number of women in the cohort with an abnormal result who are recalled for at least one biopsy (fine needle aspiration, core or open).

   False positives: calculated by subtracting the number of breast cancers detected from the abnormal recall rate.

   Breast condition: the estimated number of women in the cohort who receive a confirmed diagnosis of ductal carcinoma in situ (DCIS) during the full screening period.

   Invasive breast cancer: the estimated number of women in the cohort who receive a confirmed diagnosis of invasive breast cancer during the full screening period.

   Early stage breast cancer: the estimated number of women in the cohort whose breast cancer is diagnosed as an early stage (Tumor, Node, Metastasis ( TNM ) rating I-II). Cancer detected at earlier stages has more treatment options, less recurrence, and improved survival.

   Interval cancers: includes the estimated number of women in the cohort who become symptomatic >12 months after their last regular screen and before their next scheduled screen as well as any breast cancer that took >6 months to diagnose.

   For more information on breast cancer screening mammography in Canada, refer to Organized Breast Cancer Screening Programs in Canada: Report on Program Performance in 2003 and 2004. Ottawa: Minister of Public Works and Government Services Canada, 2008.

2. Mammography Screening Effects on Mortality

   The goal of breast cancer screening mammography is to reduce mortality (death) from breast cancer. For the 40 to 49 and 50 to 69 year age groups in the Markov risk/benefit model, a 5-year gradual mortality benefit for screening was applied. For the 70 to 79 year age group, full mortality benefit was applied immediately as it was assumed women of this age group followed recommended biennial screening between 50 to 69 years of age. For the scenario where women stop screening at 70 years of age, a gradual reduction in mortality benefit was applied.

   Relative risk reduction ( RRR ) was estimated to be 23%, 37% and 37% for each respective age group as described below:

   40 to 49 years: Meta-analysis has shown a relative risk reduction ( RRR ) of deaths from breast cancer of women aged 40 to 49yrs to be between 7 and 23%.¹ After adjustment for compliance, it is reasonable to use a RRR of 23% for those women who actually attend for screening.² This value is supported by a model of screening outcomes conducted in Australia³ as well as a recent randomized control trial showing mortality reduction adjusted for non-compliance in this age group at 24%.⁴

   50 to 69 years: Meta-analyses have shown a relative risk reduction of deaths from breast cancer of approximately 25% for women aged 50 to 69 years.^{5, 6} In order to reflect the likely impact on women who actually attend regular screening, a compliance adjusted relative risk reduction of 37% was used.²

   70 to 79 years: As the model assumes women over 70 years are continuing regular biennial screening, and the mortality benefit of screening is seen 5 years after the first screening visit (while in their 50s), it can be deduced that a woman in the 70 to 79 year age group will experience the same benefit as those 50 to 69 years of age if the woman’s life expectancy is 5 years or more. This is supported by evidence from a large trial in Sweden showing screening is as effective in reducing mortality from breast cancer in women aged 65 to 69 as it is in women aged 50 to 64.⁷ Although limited, published literature has estimated the relative mortality benefit in those over 70 years of age to be lower than that for those aged 50 to 59 years.^{8, 9} This is because relative to younger women, older women have a reduced life expectancy. However, the risk/benefit model allows for declining life expectancy by including the annual risk of death from any cause as the cohort ages. Similar assumptions were made by two other screening mammography Markov models.^{3, 10}

   Deaths prevented: The number of lives extended as a result of screening is 1, 5 and 2.5 lives for the 40 to 49, 50 to 69 and 70 to 79 years cohorts of 1,000 women respectively. These results are comparable to those using data from Breast Screen Australia (0.5, 5, 2 lives).³ However, in order to share the most accurate modeled values for readers of the decision aid, numbers have not been rounded up to the whole, but rather presented as the number of women who would need to be screened to prevent one death.

   Deaths from breast cancer: the estimated number of women who die of breast cancer within the 10 year or 20 year screening period (40 to 49/70 to 79 and 50 to 69 age groups respectively) despite their efforts to screen. This number is not a percentage of the total 1,000 women cohort, but rather from within the number of women needing to be screened to save one life. This is specific to each age group. Data on deaths among women in each of the three age groups due to breast cancer for 2000–2004 were obtained from Statistics Canada.

   Deaths from other causes: the estimated number of women who die of causes other than breast cancer within the 10 year or 20 year screening period (40 to 49/70 to 79 and 50 to 69 age groups respectively). This number is not a percentage of the total 1,000 women cohort, but rather from within the number of women needing to be screened to save one life. This is specific to each age group. Data on deaths among women in each of the three age groups due to all other (non-breast cancer) causes for 2000–2004 were obtained from Statistics Canada.

3. Breast Cancer Risk Factors

   Upon review of current scientific evidence on the relative risk (RR) values for breast cancer risk factors, each was placed into either a major (RR≥2) or minor (RR<2) category. Risk factors specific to very high risk or select sub-groups were not included. References can be found in the decision aid reference list.

Technical Notes References

1. Armstrong K, Moye E, Williams S, Berlin J, Reynolds E. Screening mammography in women 40 to 49 years of age: A systematic review for the American College of Physicians. Annals of Internal Medicine. 2007; 146:516-26.
2. Glasziou PP. Meta-analysis adjusting for compliance: the example of screening for breast cancer. Journal of Clinical Epidemiology. 1992; 45:1251-6.
3. Barratt A, Howard K, Irwig L, Salkeld G, Houssami N. Model of outcomes of screening mammography: information to support informed choices. British Medical Journal. 2005; (7497):936-8.
4. Moss SM, Cuckle H, Evans A, Johns L, Waller M, Bobrow L. Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years’ follow-up: a randomized control trial. The Lancet. 2006; 368:2053-60.
5. Kerlikowske K, Grady D, Rubin SM, Sandrock C, Ernster VL. Efficacy of screening mammography: a meta-analysis. Journal of American Medical Association. 1995; 273(2):149-54.
6. Nystrom L, Andersson I, Bjurstam N, Frisell J, Nordenskjold B. Long-term effects of mammography screening: updated overview of the Swedish randomized trials. The Lancet. 2002; 359:909-19.
7. Chen HH, Tabar I, Fagerberg G, Duffy SW. Effect of breast cancer screening after age 65. Journal of Medical Screening. 1995; 2(1):10-14.
8. Barratt A, Irwig L, Glasziou P, Salkeld G, Houssami H. Benefits, harms, and costs of screening mammography in women over 70 years of age: a systematic review. Medical Journal of Australia. 2002; 176:266-71.
9. Cox, B. The effect of service screening on breast cancer mortality rates. European Journal of Cancer Prevention. European Journal of Cancer Prevention. 2008; 17(4):306-311.
10. Kerlikowske K, Salzmann P, Phillips KA, Cauley JA, Cummings SR. (1999). Continuing screening mammography in women aged 70-79 years. Impact on life expectancy and cost-effectiveness. JAMA, 282:2756-63