What are the pros and cons of breast cancer screening?
Breast cancer screening saves lives. According to the Canadian Cancer Society, the death rate from breast cancer has been declining since the 1980s. This is thanks to earlier detection from regular mammogram screening and improvements in breast cancer treatment.
Mammography is a type of X-ray exam that takes an image of the inside of the breasts – called a mammogram. It’s the best way to detect breast cancer in its early, most treatable stage because it provides a detailed look at the internal structure of breast tissue in both men and women and can reveal changes that are too small to feel. A mammogram can be used for diagnostic concerns and for screening purposes.
Diagnostic mammography is performed if there are symptoms of a breast abnormality, while screening mammography occurs when there is no obvious breast abnormality and no signs of breast cancer. Having regular screening mammograms makes it easier to compare the images year after year and to see changes within the breast that might indicate cancer.
Screening mammograms are mostly performed on women; men generally receive a diagnostic mammogram if imaging is needed to investigate for any new concerns. Some men who are considered high risk because of a genetic predisposition are encouraged to under go regular screening. Many women start having regular screening mammograms every year at about age 40.
CANADIAN SCREENING RECOMMENDATIONS
Mayfair Diagnostics recommends screening mammography every year from age 40 to 49, then every two years between age 50 and 75, if there are no risks factors that would necessitate a shorter interval. After age 75, screening frequency will depend on a number of factors, including your medical history.
Across Canada the recommended age to start screening and the recommended screening intervals differ by province. Most provincial and federal breast screening guidelines are based on an evaluation of whether the benefits of regular screening mammograms outweigh the potential harms.
WHAT ARE THE RISKS OF REGULAR BREAST SCREENING?
When deciding between the benefit of early detection of breast cancer and the potential harms associated with breast screening there are two main harms that are often considered. The first is radiation exposure and the second is overdiagnosis.
Many women are concerned about the cumulative effects from radiation exposure during a mammogram. However, mammograms require a very small dose of radiation – the same amount of radiation as every person receives from the earth's natural background radiation over six months. Since the risk of harm from this amount of radiation exposure is low compared to the prognosis when breast cancer is detected early, many women decide the benefit outweighs the risk.
Overdiagnosis includes unnecessary treatment of cancer that would not have caused harm in a woman’s lifetime, as well as the physical and psychological consequences of false positives. Current research puts the risk of overdiagnosis at 10 percent, compared to research that shows not participating in screening mammography leads to a 60 percent higher chance of dying from breast cancer.
WHAT ARE THE BENEFITS OF SCREENING?
Early detection is the primary reason for screening. When breast cancer is detected through imaging and before it is clinically apparent (e.g. palpable lump), it is more likely to be small and more easily treated. Small cancers detected early can be removed and breast conserving surgery can be performed. Additionally, small cancers often do not require chemotherapy or radiation therapy.
WHAT ARE THE RISK FACTORS FOR DEVELOPING BREAST CANCER?
Factors that can increase the risk of developing breast cancer include women with a personal history of, or one or more first-degree relatives (parent, sibling, child) diagnosed with, breast or ovarian cancer; women who are carriers of gene mutations, such as BRCA1 or BRCA2, or have a first-degree relative with these gene mutations; and women who have had chest radiation therapy before age 30 or within the past eight years.
Women with these risk factors are considered high risk and may be encouraged to start screening earlier and more frequently.
Increasingly, breast density is being recognized as a significant risk factor. Dense breast tissue refers to how it appears on the mammogram based on the mix of fatty and fibrous tissue. Women with very dense breasts may require a more personalized screening approach than what is recommended for the general population. This may include both mammography and ultrasound exams.
While the recommendations differ and can be confusing, the ultimate decision rests with women. Understanding the risks and benefits of regular mammogram screening and speaking with your doctor about your medical history, is an important first step to decide what’s right for you.
Mayfair Diagnostics has 11 locations which offer mammography exams, including Mahogany Village, Market Mall, Mayfair Place, and Southcentre locations which have the new Pristina mammography system – which helps provide a more comfortable mammogram. Visit our breast imaging page for more information.
Canadian Association of Radiologists (2016) “CAR Practice Guidelines and Technical Standards for Breast Imaging and Intervention.” www.car.ca. Accessed September 25, 2019.
Canadian Society of Breast Imaging (2018) The Canadian Society of Breast Imaging response to the new CTFPHC Guidelines. www.csbi.ca. Accessed September 13, 2019.
Coldman, A., et al (2014) “Pan-Canadian Study of Mammography Screening and Mortality from Breast Cancer.” Journal of the National Cancer Institute. November 2014, 106 (11).
Monticciolo, Dr. et al. (2018) “Current Issues in the Overdiagnosis and Overtreatment of Breast Cancer.” American Journal of Roentgenology. February 2018, 210 (2). Accessed September 23, 2019.
Tabar, L., et al. (2018) “The incidence of fatal breast cancer measures the increased effectiveness of therapy in women participating in mammography screening.” Cancer. Accessed September 23, 2019.