Cancer screening is great, but it's not perfect. According to a new report, just 14% of all diagnosed cancers in the US are detected with a recommended screening test, while 15% of screenable cancers aren't detected by screening. The vast majority of cancers are actually found when a person presents with symptoms or seeks medical care or imaging for other reasons, according to the report by NORC at the University of Chicago, which has not been peer-reviewed. The findings "shocked" the group's senior vice president, Caroline Pearson, one of the report's authors. "We talk so much about cancer screening that we imagine that that's how all cancers are diagnosed," she tells CNN. Yet some 57% of diagnosed cancers don't have recommended screening tests, according to the report.
The US Preventive Services Task Force recommends screening tests for breast, cervical, colorectal, and lung cancers. Using 2017 data from the National Cancer Institute, National Health Interview Survey, CDC, and other sources to develop a model to calculate the rate at which cancers are detected through screening, researchers found tests detected 61% of breast, 52% of cervical, 45% of colorectal, and just 3% of lung cancers. Pearson expects these rates have only declined during the coronavirus pandemic. A separate study published last month in JAMA Oncology found the rate of cancer screenings fell significantly during the pandemic and had failed to reach prepandemic levels as of December 2021, per the ASCO Post. The reported prevalence of cancers also decreased.
Interestingly, NORC researchers found screening for prostate cancer, which isn't widely recommended, detected 77% of those cancers. These tests "do save lives, but we need to be able to save more lives," Dr. Otis Brawley, an oncology professor at Johns Hopkins University who wasn't involved in the research, tells CNN. "Everyone has been led to believe that screening is better than it actually is" when "a lot of patients are diagnosed with cancer after a negative screening test." As screening results in a 25% reduction in breast cancer mortality and only 60% of women ages 50 to 70 get screened in the US, "we can only prevent about 15% of the deaths destined to occur," he adds. Pearson says she hopes to highlight the need for better tests, as well as more data on diagnoses. (Read more cancer screening stories.)