Breast Cancer Screening

Last year the Canadian Cancer Society estimated 23,400 Canadian women would be diagnosed with breast cancer and about 5,100 would lose their lives because of it. Women have armed themselves against breast cancer by following breast exam guidelines designed to mitigate the effects of a cancer diagnosis.

Recently, however, the Canadian Task Force on Preventive Health Care released new—and controversial—guidelines for breast cancer screening. What does this mean for you, and what are the alternatives available?

Canadian Task Force on Preventive Health Care guidelines

Mammography

• Women aged 40 to 49: routine screening is not recommended
• Women aged 50 to 74: routine screening every 2 to 3 years recommended

Breast MRI

• Not recommended for routine screening

Regular breast exam performed by a doctor

• Not recommended for routine screening

Regular self breast exam

• Not recommended

These new guidelines are intended for women between the ages of 40 and 74 who have an average (not high) risk of breast cancer. In developing these guidelines, key points that were considered included the ability of a particular screening procedure to reduce deaths from breast cancer compared to its ability to cause harm (from unnecessary testing and treatments).

These guidelines have been greeted with controversy because some of the recommendations conflict with what women have been advised to do in the past and/or are in conflict with what some still believe is the correct course of action for screening.

The good thing about guidelines is that they are just that, a guide. Health care practitioners are still free to recommend the course of action they feel is best for a particular patient.

Below are some points to consider about the most common breast cancer screening techniques. These points will help women to have an informed discussion with their health care practitioners about what screening methods may be best for them.

Mammograms

Pros:

• fairly accurate compared to other screening methods
• widely available
• well studied

Cons:

• discomfort due to need to compress breasts during procedure
• exposure to radiation; mutations can cause breast cancer, especially if exposed before age 30 years; latency is more than 10 years, and the increased risk persists lifelong
• may have trouble properly screening breasts that are dense or that have had surgery or some types of augmentation

Ages 50 to 74
Among women with average breast cancer risk, those between the ages of 50 and 74 have been determined to derive the most benefit from mammograms, with the lowest risk.

To save one life from breast cancer, 1,170 women in this age group would need to be screened using mammograms every two to three years over an 11-year period. In this same group of women there would be 300 false positive results leading to additional testing and potential for unnecessary treatment, including 37 unnecessary breast biopsies.

However, the potential benefit for this age group is considered to outweigh the potential for harm.

Ages 40 to 49
Compare these numbers to those for women aged 40 to 49: 2,100 women would need to be routinely screened to save one life over an 11-year period. This would result in 690 false positive results, and 75 women would have unnecessary breast biopsies.

The risk in this age group has therefore been concluded (by the task force) to be too high to justify routine screening.

However, if you are that one woman in 2,100 whose life could be saved, or if she is your mother, sister, or daughter, you may think the risk of an extra test or treatment that is not life threatening is worthwhile.

This is what makes some guidelines controversial and why even these guidelines include options for elective screening for women who decide they are willing to accept these potential risks if it offers even the smallest chance of catching a cancer early.

In addition, some researchers argue that mammography screening in women 39 to 49 has the potential to reduce breast cancer deaths in this group by about 17 percent, while others have estimated the reduction in cancer deaths could be as high as 25 percent.

Self- or physician-performed breast exam

Pros:

• hands on and low tech
• helpful in monitoring changes in breast health

Cons:

• additional tests following false positives
• false reassurance from false negatives leading to delay in diagnosis

The task force does not recommend either routine self- or doctor-performed breast exams as a means of screening for breast cancer.

A 2005 review concluded that self breast exams did not reduce the risk of dying from breast cancer but were associated with a two-fold increase in false positives, biopsies that turn out to be benign, and visits to doctors offices.

Doctor-performed breast exams, on the other hand, were associated with a potential for death reduction from breast cancer.

Despite the task force recommendations, many still advocate for self- and doctor-performed breast exams. Although there may be debate about their impact on preventing death from breast cancer, they certainly have value in breast cancer detection in some women. Breast exams are also valuable for identifying and monitoring any changes in breast health over the years.

As in the case of mammograms, women may have differing opinions on their willingness to accept potential increase in risk (extra doctor visits, tests, or biopsies) for the peace of mind they derive from being more familiar with changes in their breasts.

Genetic testing

As many as 10 percent of breast cancers are caused by genetic factors. Among these factors is a mutation in one of two genes known as BRCA1 and BRCA2.

Women with mutations in these genes are considered to be at higher risk for breast and ovarian cancers, and women with a strong family history of breast cancer are encouraged to undergo regular screening in order to increase their chances of detecting breast cancer earlier.

Pros:

• relief with negative result
• proactive measures can be considered with positive result

Cons:

• positive result can cause anxiety or depression

Whether or not to undergo this testing is an individual decision. Many women would rather not live with the increased stress of knowing they have a higher risk of breast cancer. Others definitely want to know so that they can take any and all precautions and undergo regular screening.

Thermography

This is a form of thermal imaging that detects temperature differences in breast tissue. These temperature differences may be associated with changes in tissue metabolism and circulation, some of which are believed to occur in early tumour development.

Pros:

• does not expose the body to radiation
• does not require the breasts to be compressed as in mammograms

Cons:

• must be performed in a temperature-controlled environment to improve accuracy of results
• not currently accepted as a screening tool for breast cancer by most cancer authorities

The main concern over this form of screening is its current lack of study compared to mammography and the inability for it to be used alone as a screening tool. Although changes in tissue temperature can certainly correlate with illness in some tissues, it does not necessarily mean a cancer is present (or that one will develop), and additional tests will still be required.

The accuracy of thermography (compared to mammography) has been questioned in studies such as a June 2011 article that reported a low sensitivity of the test. A low sensitivity means a potential to miss what the test is looking for.

In this study of 63 women with breast disease, 15 diagnoses were missed by thermography, 16 false positives occurred, five diagnoses were properly identified, and 90 tests were correctly identified as normal, healthy breast tissue.

The researchers concluded that, although breast thermography had the advantage of being noninvasive, it was not accurate enough to be used as the sole breast cancer screening method.

Breast MRI

Magnetic resonance imaging (MRI) screening of the breast is generally done only as an adjunct to mammography and other screening methods and for women who carry the BRCA1 or BRCA2 gene mutation.

Pros:

• does not use X-ray
• does not require compression of the breasts
• generally more sensitive than mammography for detecting abnormalities

Cons:

• long wait times for appointments
• not as widely available
• not considered as well proven as mammography for women 40 to 74 at average risk for breast cancer

Where MRI shines is in the screening of women at increased risk of breast cancer, where it has been shown to outperform all other commonly used methods of screening. In high-risk women MRI is more sensitive for detecting cancers, and MRI screening is associated with a reduction in the development of advanced stage cancers, due to earlier detection. 

Risk factors for breast cancer

• age—being over 50; risk of a breast cancer diagnosisincreases with age
• genetics—a mutation in the genes known as BRCA1 or BCRA2 increases the risk of breast cancer significantly
• smoking
• dense breast tissue
• a first-degree relative (mother, sister) with breast cancer
• high exposure of the chest to X-rays or other radiation
• use of hormone replacement therapy for more than five years
• while using birth control pills, and for 10 years after you stop
• drinking more than one alcoholic beverage per day
• menopause after age 55
• menses before age 12
• having children after age 30, or not having children at all

Things you can do to reduce your risk

• Exercise regularly.
• Don’t smoke.
• Be moderate with alcohol intake.
• Avoid long-term use of hormones.
• Eat a diet rich in vegetables, fruit, and lean proteins.