A large retrospective cohort study conducted by researchers from Yale School of Medicine in New Haven, Connecticut, has shed light on the significant risk of overdiagnosis among older women who are screened for breast cancer. According to the study, approximately 31% of breast cancers among women aged 70 to 74 were potentially overdiagnosed. This percentage increased with advancing age, with 47% of cases potentially overdiagnosed among women aged 75 to 84, and a startling 54% among women aged 85 and older.
Age and Life Expectancy as Factors
The study also revealed that the risk of overdiagnosis varied based on life expectancy. Among screened women with a life expectancy of more than 10 years, approximately 32% of breast cancers were potentially overdiagnosed. This percentage increased to 53% for women with a life expectancy of 6 to 10 years, and a shocking 63% for women with a life expectancy of 5 years or less. These findings highlight the need for considering overdiagnosis when making screening decisions, as well as evaluating the potential benefits of screening.
Unchanged Breast Cancer-Specific Death Rates
Contrary to previous beliefs, the study did not find statistically significant reductions in breast cancer-specific death rates associated with screening in women aged 70 and older. This raises an important question about whether the harms of overdiagnosis outweigh the benefits of screening in this population. The authors of the study emphasize the need for explicit consideration of overdiagnosis when making screening decisions, taking into account patient preferences, risk tolerance, comfort with uncertainty, and willingness to undergo treatment.
In an accompanying editorial, experts from the Johns Hopkins University in Baltimore underline the distinction between discussing overdiagnosis of breast cancer and determining whether mammography saves lives. They argue that high-quality, routine mammography programs do save lives, at least for women in the age group evaluated in the study (70 and older), as well as for women aged 40 to 80. However, they caution that the public messaging often fails to emphasize the importance of high-quality and routine mammography programs.
The editorialists further note that until objective prognostic markers are developed to identify indolent types of cancer, physicians and patients should be aware that a small but significant proportion of those “cured” of cancer may not have needed treatment in the first place. They highlight the importance of developing an effective, objective test that would spare these women the inconvenience of unnecessary therapy.
Towards a 21st-Century Definition of Cancer
Finding a solution to the overdiagnosis problem necessitates further research into cancer genomics. The editorialists propose moving towards a 21st-century definition of cancer that takes into account both the biopsy and pathologic appearance as well as genomics. This updated definition would recognize that breast cancer is not a single entity but rather a collection of different diseases with potentially distinct patterns of behavior, requiring tailored treatments and sometimes no treatment at all.
Study Details and Key Findings
The study conducted by the researchers at Yale School of Medicine involved comparing the cumulative incidence of breast cancer among women aged 70 and older who continued to undergo screening with those who did not. The analysis included 54,635 women with a mean age of 77.2 years. Among the cohort, 41% had a life expectancy of 10 years or less, and 15% were considered frail.
The findings revealed that the cumulative incidence of breast cancer was higher among screened women compared to those who were not screened. The absolute risk difference between these two groups remained consistent across different age groups, ranging from 1.5 to 2.3 cases per 100 women screened.
This critical analysis highlights the significant risk of overdiagnosis among older women screened for breast cancer. The study’s findings raise important questions about the balance of benefits and harms associated with screening in this population. Moving forward, it is crucial to consider overdiagnosis explicitly when making screening decisions and to take into account patient preferences and individual risk factors. Additionally, further research into cancer genomics and the development of objective prognostic markers are needed to address the problem of overdiagnosis and achieve more personalized and effective breast cancer screening and treatment strategies.
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