A study of more than 50,000 women found that continued breast cancer screening after age 70 was associated with a greater incidence of cancer that likely would not have caused symptoms in the patient’s lifetime. These findings suggest that overdiagnosis may be common among older women who are diagnosed with breast cancer after screening. The study is published in Annals of Internal Medicine.

Clinical guidelines advising screening in older women vary because the balance of benefits and harms of screening in this population is unclear. Some previous research has indicated that the mortality benefit of screening may be limited to women under the age of 75. Possible harms of screening in older women include frequent false positives that require invasive testing and procedures, and overdiagnosis itself is now considered an important additional harm from screening. Overdiagnosis may be defined as detecting a cancer, often through screening, that would not have caused symptoms in a person’s lifetime.

Researchers from the Yale School of Medicine conducted a retrospective cohort study of 54,635 women aged 70 years and older who had been recently screened for breast cancer. The authors found that the risk of overdiagnosis increased significantly with age. They report that among women aged 70 to 74, up to an estimated 31% of breast cancer found among screened women was overdiagnosed. In women aged 74 to 84 years, up to 47% of breast cancer found among screened women was overdiagnosed. They also found that the risk of overdiagnosis was highest in women aged 85 years and older, who experienced up to a 54% rate of overdiagnosis. The authors note that they did not see statistically significant reductions in breast cancer-specific death associated with screening. These findings suggest that overdiagnosis should be explicitly considered when making screening decisions, along with considering possible benefits of screening.

Further reading: Genetic Profiling May Identify Breast Cancer Patients Who Can Omit Radiation Therapy

An accompanying editorial by authors from Johns Hopkins University highlights the frequency of overdiagnosis from cancer screening and the harms of overdiagnosis. The authors add that additional overdiagnosis harms include the risk of complications from overtreatment, unnecessary anxiety, financial hardship, and unnecessary consumption of limited resources. They argue that the answer to the problem of overdiagnosis is further study of genomics and improved understanding of the biopsy and pathologic appearance of cancer.