SDI Productions/Getty Images
Do cancer screening tests actually save lives by extending lifespans? It's a complicated question, but new research points to no—with at least one exception.
Cancer screening guidelines have been at the forefront of preventative care for decades; going to the doctor for regular mammograms, colonoscopies, or other screenings is highly recommended by healthcare professionals, medical organizations, and patient advocacy groups.
But emerging research has shown certain screenings may have uncertain benefits, or could even pose unnecessary harms to patients.
In a new series of articles published last month in JAMA Internal Medicine—spearheaded by a study involving more than 2.1 million patients—researchers took on the question of whether cancer screening tests, like those for colon, breast, and prostate cancers, could actually add a significant number of years to a person's lifespan.
The findings showed that, outside of a certain colorectal cancer screening called a sigmoidoscopy, screening tests do not appear to save lives by increasing longevity.
It's important to note that the research doesn't imply cancer screenings aren't useful—just that blanket statements about cancers screenings' ability to "save lives" may not be entirely accurate, according to first study author Michael Bretthauer, MD, PhD, a professor of medicine at the Institute of Health and Society at the University of Oslo.
“I think it’s up to everybody to decide if that’s something that is meaningful to them or not,” Bretthauer told Health.
Here’s what experts had to say about the efficacy of cancer screenings, limitations associated with the research, and why it's important to weigh the pros and cons associated with screening tests.
According to Bretthauer, the new study was inspired by his own observation of ads and slogans claiming that cancer screening saves lives.
“What does it mean, ‘saving your life,’ or ‘saving somebody’s life,’ or 'saving life' in general?" he asked. "The only logical explanation would be to live longer with screening than without screening.”
To determine if these life-saving claims were accurate, the researchers looked at 18 randomized clinical trials that, in total, included over 2 million individuals. These trials included sigmoidoscopy, colonoscopy, and fecal testing, which all test for colorectal cancer. Trials on mammography for breast cancer, lung cancer screening, and prostate-specific antigen (PSA) testing for prostate cancer were also included in the analysis.
Each studied individual trial included information on the lifespans of people who were screened for specific cancers and those who were not. The difference between those two numbers was deemed longevity added by a certain screening test.
“[For] most of the screening tests, there was really no meaningful extension of life,” said Bretthauer.
The study did find that sigmoidoscopy—using a scope to inspect the sigmoid colon—extended life by about three months, which isn’t necessarily a surprise, as it's one of the best, Otis Brawley, MD, professor of oncology and epidemiology at Johns Hopkins Medicine, told Health.
Colonoscopy and prostate cancer screening were associated with living 37 days longer, and lung cancer screening was linked to a 107 bump in longevity. However, these results were deemed “uncertain."
Mammography and fecal testing for colorectal cancer both added zero days to people’s overall longevity.
The study's findings may seem shocking considering how common cancer screenings are. However, Bretthauer clarified: “This study was not really about if screening works."
It’s well-established that screening tests allow doctors to find cancers before they progress to worse stages. This can lead to better survival outcomes and quality of life for patients.
Catching cancer early can also change treatment options—for example, a stage one cancer might be removed with surgery and radiation, while later-stage cancers could require more invasive treatments such as chemotherapy.
So cancer screenings are beneficial for the overall health of Americans. But saying these tests "save lives" appears to be an exaggeration.
"This was about the slogan," said Bretthauer, noting that the slogan did not hold up. "To use that powerful slogan in medicine—which is such a serious business for all of us—I think it needs to be true."
Bretthauer's study has seen a fair amount of pushback online—both essays and comments on the study itself criticize the interpretations and study design.
The study itself does admit some limitations—for one, participants were followed for just over a decade, so it’s possible that the researchers would’ve seen a greater increase in longevity had they been followed for longer.
Still, research that critiques cancer screening shouldn't be immediately dismissed—people tend to overestimate these tests, Brawley said.
For instance, colorectal screening is considered one of the best tests out there for both preventing and reducing death from the disease. Historical research has shown that colonoscopies can yield a 40–69% decrease in disease incidence and a 29–88% decrease in colon cancer-related deaths.
However, newer research shows those numbers may be overestimates. A 2022 study published in the New England Journal of Medicine found that colonoscopy screenings only cut the risk of colorectal cancer 18%—far lower than previous research had found. Colonoscopies also appeared to have little effect on reducing the risk of death from colon cancer.
The newest research also addresses the fact that screening tests do come with their own risks and possible side effects.
Though it's often under-reported, cancer screenings can cause radiation exposure that Brawley said may cause cancer, false-positive results that can lead to unnecessary treatments and complications, and other issues. The National Cancer Institute points out that few guidelines give a clear idea of how many people experience harm associated with a particular screening method.
“Some people are dying from surgery, some people are dying from chemotherapy, some people are dying from radiation—that’s well known,” said Bretthauer.
According to Brawley, this may explain why the study found what it did. If someone loses their life from a complication of cancer screening at age 50, for example, it numerically outweighs the five years added to someone’s life because their cancer was caught earlier.
But, trying to make these types of comparisons can quickly become complicated.
Though this study shows that cancer screenings may not be improving longevity, the takeaway isn't to avoid them.
For mammography, Brawley said, the fact that it doesn't prolong life “doesn’t mean that we shouldn’t be doing breast cancer screening. It means that we need to try to do breast cancer screening better.”
Reducing the harm that may come from screening is an important piece of the conversation, Bretthauer added. But he’s less optimistic.
“There may be something in the future with new therapies [that] are less harmful, that brings us to a positive sum,” he said. “We’re not there, and I don’t know if we’re going to get there.”
In the meantime, educating people on the benefits and risks associated with cancer screenings is important. Bretthauer suggests that doctors present patients with their risk of dying from certain cancers and how helpful screening is overall so that they can make an informed decision.
Brawaley emphasized that this is just one piece of research.
"People who are concerned about screening and concerned about cancer should rely upon the experts who read all of this literature, not just this one trial," said Brawley. "The U.S. Preventive Services Task Force is a wonderful group of experts. And I would rely upon their recommendations."
