Mammograms – the why, when and how often’s
Breast cancer is the most frequent type of non-skin cancer and the most frequent cause of cancer death in women worldwide
The majority of breast cancers are diagnosed as a result of an abnormal screening study, although a significant number are first brought to attention by a patient. Findings suggest that screening mammography both reduces the odds of dying of breast cancer and facilitates the use of early treatment
What is a mammogram?
Mammography is the process of using low-energy X-rays(usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through the detection of characteristic masses or microcalcifications.
What are the benefits and potential harms of screening mammograms?
Early detection of breast cancer with screening mammography means that treatment can be started earlier in the course of the disease, possibly before it has spread. Results from randomized clinical trials and other studies show that screening mammography can help reduce the number of deaths from breast cancer among women ages 40 to 74, especially for those over age 50. However, studies to date have not shown a benefit from regular screening mammography in women under age 40 or from baseline screening mammograms (mammograms used for comparison) taken before age 40.
The benefits of screening mammography need to be balanced against its harms, which include:
False-positive results. False-positive results occur when radiologists see an abnormality (that is, a potential “positive”) on a mammogram but no cancer is actually present.
False-positive mammogram results can lead to anxiety and other forms of psychological distress in affected women. The additional testing required to rule out cancer can also be costly and time-consuming and can cause physical discomfort.
False-positive results are more common for younger women, women with dense breasts, women who have had previous breast biopsies, women with a family history of breast cancer, and women who are taking estrogen (for example, menopausal hormone therapy
Overdiagnosis and overtreatment. Screening mammograms can find cancers and cases of ductal carcinoma in situ(DCIS, a noninvasive tumor in which abnormal cells that may become cancerous build up in the lining of breast ducts) that need to be treated. However, they can also find cases of DCIS and small cancers that would never cause symptoms or threaten a woman’s life. This phenomenon is called “overdiagnosis.” Treatment of overdiagnosed cancers and overdiagnosed cases of DCIS is not needed and results in “overtreatment.”
Because doctors cannot easily distinguish cancers and cases of DCIS that need to be treated from those that do not, they are all treated.
False-negative results. In cancer screening, a negative result means no abnormality is present. False-negative results occur when mammograms appear normal even though breast cancer is present. Overall, screening mammograms miss about 20% of breast cancers that are present at the time of screening. False-negative results can lead to delays in treatment and a false sense of security for affected women.
One cause of false-negative results is high breast density. Breasts contain both dense tissue (i.e., glandular tissue and connective tissue, together known as fibroglandular tissue) and fatty tissue.
False-negative results occur more often among younger women than among older women because younger women are more likely to have dense breasts. As a woman ages, her breasts usually become fattier, and false-negative results become less likely.
Some breast cancers grow so quickly that they appear within months of a normal (negative) screening mammogram. This situation does not represent a false-negative result, because the negative result of the screening was correct. But it means that a negative result can give a false sense of security. Some of the cancers missed by screening mammograms can be detected by clinical breast exams (physical exams of the breast done by a health care provider).
Finding breast cancer early may not reduce a woman’s chance of dying from the disease. Even though mammograms can detect malignant tumors that cannot be felt, treating a small tumor does not always mean that the woman will not die from cancer. A fast-growing or aggressive cancer may have already spread to other parts of the body before it is detected. Instead, women with such tumors live a longer period of time knowing that they likely have a potentially fatal disease.
In addition, finding breast cancer early may not help prolong the life of a woman who is suffering from other, more life-threatening health conditions.
Radiation exposure. Mammograms require very small doses of radiation. The risk of harm from this radiation exposure is low, but repeated x-rays have the potential to cause cancer. Although the potential benefits of mammography nearly always outweigh the potential harm from radiation exposure, women should talk with their health care providers about the need for each x-ray. In addition, they should always let their health care provider and the x-ray technologist know if there is any possibility that they are pregnant because radiation can harm a growing fetus.
When and how often should I have a mammogram?
Current screening protocols for an average-risk woman are similar worldwide. No programs begin screening women before age 50 and few have shorter than 12–18-month screening intervals. Most advocate screening from age 50 and longer screening intervals (24–36 months). The American College of Radiology (ACR) has the longest recommended age range for screening and is the only one recommending annual screening. The UK has the longest recommended screening interval at three years.
The World Health Organization (WHO) recommends two-yearly screening in large, national-based screening programs.
South African recommendations have historically been based on American guidelines, some of which changed in 2009, again in 2016 and most recently April 2019.
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Society and expert recommendations for routine mammographic screening in women at average risk
|Group (date)||Frequency of screening (years)||Initiation of screening for women at average risk|
|40 to 49 years of age||50 to 69 years of age||≥70 years of age|
|US Preventive Services Task Force (2016)||Two||Individualize*||Yes||Yes, to age 74|
|American College of Obstetricians and Gynecologists (2017)||One to two*||Individualize*||Yes||Yes, to at least age 75|
|American College of Physicians (2019)||Two||Individualize*||Yes||Yes, to age 74|
|American Academy of Family Physicians (2019)||Two||Individualize*||Yes||Yes, to age 74|
|American Cancer Society (2015)||One year age 45 to 54||Individualize* through age 44
Yes, start age 45
|One to two years age ≥55|
|American College of Radiology (2017)||One||Yes||Yes||Yes|
No matter who you are or what your risk factors are, the best option is to have an open discussion with your family doctor about any questions or concerns you might have.