According to a new report, a small proportion – 14.1% – of all cancers diagnosed in the United States are detected by screening with a recommended screening test.
The remaining diagnosed cancers tend to be discovered when a person has symptoms or seeks imaging or medical care for other reasons, suggests the report, posted online Wednesday by researchers from the nonprofit research organization nonprofit NORC of the University of Chicago.
“I was shocked that only 14% of cancers are detected by screening. I think for a lot of people, we talk so much about cancer screening that we imagine that’s how all cancers are diagnosed. We talk about mammograms and colonoscopies all the time,” said Caroline Pearson, report author and senior vice president of the organization.
Still, “the vast majority of cancer types don’t have screening tests available,” Pearson said.
The technical report notes that only four types of cancer — breast, cervical, colorectal, and lung — have screening tests recommended by the US Preventive Services Task Force, and the percentage of cancers detected by screening varies among these types: 61% of breast cancers, 52% of cervical cancers, 45% of colorectal cancers and 3% of lung cancers. The report also includes data on prostate cancer, although prostate cancer screening is not widely recommended, and the data suggests that 77% of prostate cancers are detected by screening.
The report, which has not been published in a peer-reviewed journal, is based on data from 2017. But Pearson said studies since then have shown cancer screening rates have declined over the past few years. early days of the Covid-19 pandemic. She suspects that the percentage of cancers detected by screening could now be even lower than what was found in the new report.
“I really think the percentage of cancers detected by screening would have been lower due to the pandemic. We know people have missed a huge number of recommended screenings, and we’re seeing these cancers show up at later stages in clinical settings,” Pearson said. “So with the reduction in screenings, we’re getting fewer cancers diagnosed that way, and that’s definitely something we’ll pick up in the data.”
For the new report, Pearson and colleagues developed a model to calculate the percentage of cancers detected by screening, using data from the National Cancer Institute on the incidence of diagnosed cancers, national screening rates from the National Health Interview Survey, test rates from the US Centers for Disease Control and Prevention’s Behavioral Risk Factor Surveillance System, and several studies on the rate at which cancers are detected.
There is not much data in the medical literature on cancers detected by screening, she said, adding that she hopes the report will draw attention to the importance of cancer screening, the need more tests and the need for more data on how cancers are diagnosed, including the important role screening tests play in the early detection of cancers.
“We would benefit from much stronger data and analytics to really understand how cancer affects different populations and how we can improve equity,” Pearson said. “For researchers around the world, I would like people to dig into some of these estimates and some of the geographic variations that we see to understand how we can start to shape the public policy environment to improve treatment across the country. and improve screening across the country.
Dr Otis Brawley, a professor of oncology at Johns Hopkins University, said he was not surprised by the new report’s findings – particularly because some cancer screening tests can be improved in their performance.
“Everyone has been led to believe that screening is better than it actually is,” said Brawley, who was not involved in the new report. “We need to invest in research to try to find better tests.”
In the case of breast cancer, for example, “clinical trials tell us that screening prevents 25% of people destined to die from breast cancer from dying from breast cancer,” he said. “In the United States, about 60% of women between the ages of 50 and 70 get tested. This means that we can only prevent about 15% of the deaths that are destined to occur. It also means that many patients are diagnosed with cancer after a negative screening test.
In the United States, people could benefit from cancer prevention measures — such as getting screened and maintaining a healthy lifestyle — but the public can also benefit from better screening tests themselves, Brawley said.
“We spend so much time pushing screening and pushing testing – yes, they save lives, but we need to be able to save more lives,” he said. “We need better.”
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