Screenings May Overdiagnose Cancer in Older Women
Preventive mammograms for breast cancer may be less worthwhile for older women, according to a study published this week. The authors of the study believe that a significant percentage of cancer cases detected at screening in women over 70 are overdiagnosed, ie the discovery of a tumor unlikely to cause disease before death. In women over the age of 85, more than half of these cases may be overdiagnosed.
The research was led by researchers at Yale University’s Cancer Outcomes, Public Policy and Effectiveness Research (COPPER) Center. The team hoped to quantify the risk of a specific known downside of preventive breast cancer screening in older women: finding cancers that may not need treatment. These cancers may grow too slowly to be noticeable or occur in people who otherwise would die sooner.
They analyzed data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Medicare Registry.
In total, they examined around 55,000 women over the age of 70 with no history of breast cancer who had recently undergone mammography. Then they compared the results of women who continued to have regular screenings with those of women who had not had screenings for up to 15 years. Additional cancer cases were found in the screening group The unexamined group probably represents an overdiagnosis, the authors suspected. It’s possible that some of those extra cases got better because they got treatment, but the team also analyzed the impact of screening on breast cancer-related deaths.
At the end of the study period, about six out of 100 regularly screened women aged 70 to 74 were diagnosed with breast cancer, compared to about four out of 100 unscreened women. According to the authors’ estimates, this difference amounts to a potential overdiagnosis rate of 31%. For women between the ages of 74 and 80, the estimated rate was 47%. And for women over 85, the rate rose to 54%. Importantly, they also did not find a statistically significant reduction in the risk of reported breast cancer deaths in women who continued to be studied. The team’s results were published Tuesday in Annals of Internal Medicine.
“Overdiagnosis can occur when cancers grow very slowly or when a person’s life expectancy is short. Finding these breast cancers can be worrisome and lead to intensive treatments with no improvement in longevity or quality of life,” said lead author Ilana Richman, assistant professor of medicine at Yale School of Medicine, in one opinion from the university. “The results of this study underscore the need for a careful assessment of the benefits and harms of screening older women.”
There is a long debate about the optimal strategy for cancer screening, including mammograms. In May, the US Preventive Services Task Force — an influential body of experts that guides screening practices in the US —issued A new draft recommendation states that women with an average breast cancer risk should be screened from the age of 40 instead of the age of 50. However, the USPSTF declined to recommend mammograms for women over 74, saying the evidence for or against its use was not yet conclusive. Other groups like the American Cancer Society have done this approved regular mammograms in older women, provided they remain healthy and are expected to live at least 10 years.
While these results add weight to the argument that mammograms are less valuable for older women, the authors note that there are many other factors that people can and should weigh when making decisions about cancer screening as they age.
“Screening decisions must also consider a patient’s preferences and values, personal risk factors, and the overall balance of risks and benefits of screening,” said Richman.
