A study of more than 50,000 women found that continuing breast cancer screening after age 70 was associated with a higher incidence of cancer that would likely not have caused symptoms during 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 .
Estimation of Breast Cancer Overdiagnosis Following Screening Mammography Among Older Women in the United States Summary: Background: Overdiagnosis is increasingly recognized as a harm of breast cancer screening, particularly for older women. Aim: To estimate the overdiagnosis associated with breast cancer screening in older women by age. Design: Retrospective cohort study comparing the cumulative incidence of breast cancer among older women who continued screening at the next interval with those who did not. Analyzes used competing risk models, stratified by age. Setting: Medicare fee-for-service claims, linked to the SEER (Surveillance, Epidemiology, and End Results) program. Patients: Women aged 70 or older who have recently undergone screening. Measurements: Breast cancer diagnoses and death from breast cancer up to 15 years of follow-up. Results: This study included 54,635 women. Among women aged 70 to 74 years, the adjusted cumulative incidence of breast cancer was 6.1 cases (95% CI, 5.7 to 6.4) per 100 women screened versus 4.2 cases (95% CI, 3.5 to 5.0) per 100 unexamined women. An estimated 31% of breast cancer cases among women examined were potentially overdiagnosed. For women aged 75 to 84 years, the cumulative incidence was 4.9 (CI, 4.6 to 5.2) per 100 women screened versus 2.6 (CI, 2.2 to 3.0) per 100 women not evaluated, with 47% of cases potentially overdiagnosed. For women aged 85 years or older, the cumulative incidence was 2.8 (CI, 2.3 to 3.4) among screened women versus 1.3 (CI, 0.9 to 1.9) among screened women. No, with up to 54% overdiagnosis. We did not observe statistically significant reductions in breast cancer-specific deaths associated with screening. Limitations: This study was designed to estimate overdiagnosis, which limits our ability to draw conclusions about the full benefits and harms of screening. Unmeasured differences in breast cancer risk and differential competing mortality between screened and unscreened women may confound results. The results were sensitive to model specifications and the definition of a screening mammogram. Conclusion: Continuation of breast cancer screening was associated with a higher incidence of breast cancer, suggesting that overdiagnosis may be common among older women who are diagnosed with breast cancer after screening . Whether the harms of overdiagnosis are balanced by the benefits and for whom remains an important question. |
Comments
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 younger than 75 years . Potential harms of screening in older women include frequent false positives requiring invasive testing and procedures, and overdiagnosis itself is now considered an important additional harm of screening.
Overdiagnosis can be defined as the detection of a cancer, often through screening, that would not have caused symptoms in a person’s lifetime.
Researchers at Yale School of Medicine conducted a retrospective cohort study of 54,635 women ages 70 and older who had recently undergone breast cancer screening. The authors found that the risk of overdiagnosis increased significantly with age.
- They report that among women ages 70 to 74, up to an estimated 31 percent of breast cancer found among women screened was overdiagnosed.
- In women ages 74 to 84, up to 47 percent of breast cancer found among women screened was overdiagnosed.
- They also found that the risk of overdiagnosis was highest in women aged 85 and older, who experienced an overdiagnosis rate of up to 54 percent.
The authors note that they did not observe statistically significant reductions in breast cancer-specific deaths associated with screening. These findings suggest that overdiagnosis should be explicitly considered when making screening decisions, in addition to considering the potential benefits of screening.
An accompanying editorial by authors from Johns Hopkins University highlights the frequency of overdiagnosis of cancer screening and the harms of overdiagnosis. The authors add that additional harms of overdiagnosis include the risk of complications from overtreatment, unnecessary anxiety, financial difficulties, and unnecessary consumption of limited resources. They argue that the answer to the problem of overdiagnosis is greater study of genomics and a better understanding of the biopsy and pathological appearance of cancer.
