Cover Is 40 the age to start breast cancer screenings? Singapore-based researcher Li Jingmei offers her insight (Photo: Getty Images)
Is 40 the age to start breast cancer screenings? Singapore-based researcher Li Jingmei offers her insight (Photo: Getty Images)
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As guidelines advise women in the US to start getting mammograms at the age of 40—a decade earlier than previously recommended, Singapore-based breast cancer researcher Li Jingmei weighs in on why these guidelines may particularly apply to women in Asia and how age is not the only factor to consider
The United States Preventive Services Task Force, an independent group of experts that establishes standards for tests and screenings, recommends that women at average risk receive breast cancer screening every two years starting at age 40, instead of 50. The task force finalised the guidelines in 2024; previously, women ages 40 to 49 were advised to make an individual decision after weighing the benefits and harms of screening.
Breast cancer typically affects women who are in their middle to later years of life. Of the 264,115 breast cancer cases diagnosed in the US in 2019, 83 per cent were above the age of 50; approximately 4 per cent are detected in women under the age of 40. By lowering the mammography screening entry age by a decade, 33,582 (13 per cent) additional women between the age of 40 to 49 would have benefited from having their breast cancers detected earlier, when the tumours are small and most successfully treated.
Several other organisations that suggest mammograms beginning at the age of 40 are the National Comprehensive Cancer Network, the American College of Radiology, the American Society of Breast Surgeons, and the American College of Obstetricians and Gynecologists—though not all use the same interval.
Evolving evidence
One of the most rigorous ways to prove the effectiveness of screening mammography is through randomised controlled trials. Several such studies conducted over 10 to 18 years have shown that women between 40 to 49 years old who undergo screening mammography have a statistically significant reduction in breast cancer deaths by 15 to 18 per cent. However, a prominent Canadian study carried out in the 1980s sparked controversy by suggesting that mammograms may not be beneficial for women between 40 to 49 years old, and instead may result in unnecessary diagnosis of breast cancer. The scientific flaws of this study have since been highlighted and the results debunked.
Public health experts agree that breast imaging can save lives, but they question the value of screening mammograms.
Overdiagnosis and nonprogressive cancers
Experts suggest that for every three breast cancers detected by screening mammograms, one woman is overdiagnosed. Overdiagnosis in mammography refers to the detection of breast cancer that would never have caused symptoms or harm to the patient during their lifetime. This occurs when a screening mammogram identifies a suspicious area that is later confirmed to be cancer, but the cancer would never have grown or caused any problems if it had not been detected through screening. Overdiagnosis can lead to overtreatment, unnecessary procedures and undue emotional distress for patients.
The masking effect of mammography on younger women
False positive findings in mammograms are more common among younger women because they tend to have denser breast tissue. Dense breast tissue appears white on a mammogram, which can make it difficult to distinguish between normal tissue and potential abnormalities. As a result, the image is less clear, increasing the likelihood of benign findings that require additional imaging or biopsy to determine whether they are cancerous. Cancers can also be masked by dense tissue and missed altogether.
Limited effectiveness in younger women
Modern mammography has the highest sensitivity in women aged 50 and above, particularly those with predominantly fatty breasts. A high sensitivity means that the test is able to accurately identify a high percentage of cases where breast cancer is actually present. This is an important factor in the effectiveness of mammography screening for breast cancer. Studies show that the sensitivity of mammography is above 92 per cent for women above 50 years of age, 75 per cent for women aged 40 to 49, and 58 per cent for women below 40 years of age. In other words, mammography is not as good at detecting breast cancer in younger women compared to older women.
No universal guidelines
Worldwide, there is no uniformity among plans regarding the age and frequency at which women with an average risk of breast cancer should receive mammography. The majority of countries that have screening programmes for breast cancer recommend screening for individuals between the ages of 50 and 69, with most of these countries being in Europe. Generally, these screening programs suggest having a mammogram every two years. In the UK, the recommended screening interval is once every three years.
Asian breast cancers are “younger”
In Asian countries, there is a higher proportion of women who develop the disease at a younger age. While the peak age falls between 60 and 70 years in Western countries, it is between 40 and 50 years in Asian countries. Since the 1990s, 13 Asian countries have gradually adopted mammography screening on a population-based level. The most widely recommended screening protocol is to undergo screening every two years starting at the age of 40.
Age alone does not give a complete picture of a woman’s breast cancer risk
Whilst there are differences in the starting age and screening interval, all mammography screening programmes follow an approach based on age. However, age is not the only risk factor for breast cancer, which is a complex disease. Taking into account other breast cancer risk factors such as genetics, family history, breast density, hormone exposure, obesity and history of benign breast diseases, a 35-year-old woman could be at the same risk level as a 50-year-old woman who is encouraged to get a mammogram under all existing guidelines.
Personalising breast cancer risk estimates
Rather than using age as the sole determinant for identifying women who are at high risk of developing breast cancer, a risk-based approach involves creating an individualised breast cancer risk profile for each woman, taking into account factors such as her genetics, breast density, environmental exposures and lifestyle choices. Recommendations to manage breast health may then be tailored according to the needs of each woman. This knowledge is especially helpful for those in their forties, where the guidelines are not always clear.
Examples of risk-based breast cancer screening programmes include the Women Informed to Screen Depending On Measures of Risk (WISDOM) study in the US, and the Breast Cancer Screening Tailored for Her (BREATHE) study in Singapore. WISDOM uses a personalised risk assessment tool to determine the appropriate screening frequency for women based on their individual risk factors. BREATHE estimates breast cancer risk using different calculators to identify and target high-risk women for screening.
A call to action
Breast cancer is a serious problem for women aged between 40 to 49 years of age, especially when we consider the years of life that are lost due to the disease without proper screening. Nonetheless, a more urgent problem in many parts of the world is to get women to actually go for screening. Mass-produced uniform recommendations based on age, or couture risk profiles? The success of any screening program will ultimately depend on what women want.
