As new 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, has released draft guidelines stating that women should undergo breast cancer screening every two years beginning at the age of 40 instead of 50. Previously, women aged 40-49 were advised to weigh the benefits and harms on a personal level before deciding on whether or not to start 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 percent were above the age of 50; approximately 4 percent are detected in women under the age of 40. By lowering the mammography screening entry age by a decade, 33,582 (13 percent) 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.
The National Comprehensive Cancer Network, the American College of Radiology, the American Society of Breast Surgeons, and the American College of Obstetricians and Gynecologists are other organisations that suggest yearly mammograms beginning at the age of 40.
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 10-18 years have shown that women between 40-49 years old who undergo screening mammography have a statistically significant reduction in breast cancer deaths by 15-18 percent. 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.