Colorectal cancer, which includes cancer of the colon and rectum, is one of the most common cancers in the world.
It often develops slowly over many years and may not cause clear symptoms in the early stages.
Because of this, many people are diagnosed only after the disease has already advanced, when treatment becomes more difficult.
Doctors have long believed that screening—testing people before symptoms appear—can help find cancer earlier and save lives.
A large new study now provides strong evidence that screening really does detect more cases at an early and more treatable stage.
The research involved more than 278,000 people who were all 60 years old. Scientists from Uppsala University and Karolinska Institutet in Sweden randomly divided these participants into three groups.
One group was invited to have a colonoscopy, a medical procedure in which doctors use a thin tube with a camera to look inside the colon.
Another group was asked to take a simple home test called a fecal immunochemical test, or FIT. This test checks for tiny amounts of blood in stool samples, which can be an early sign of cancer. If the FIT test showed a positive result, those participants were then offered a colonoscopy. The third group received usual care and did not undergo special screening.
The results showed that both screening methods found more cancers at an early stage, especially during the first two years when most of the tests were performed. This is important because early-stage colorectal cancer can often be treated successfully, sometimes even cured.
In addition to finding cancer early, screening can also detect small growths called adenomas. These growths are not yet cancer, but they can turn into cancer over time. Removing them during a colonoscopy can prevent cancer from developing in the first place.
The study is part of a long-term project that began in 2014 to examine whether screening reduces deaths from colorectal cancer. Participants who took the FIT test were asked to repeat it twice over several years.
If blood was detected in their samples, doctors performed further examinations. People who had colonoscopies also received treatment if any abnormal tissue was found. Researchers tracked all participants using national health records until 2020.
By the end of the follow-up period, fewer people in the screening groups developed advanced colorectal cancer compared to those who did not receive screening. The strongest effect was seen in the FIT group.
About 0.61 percent of people in this group developed colorectal cancer, compared with 0.73 percent in the group that had no screening. Although the difference may seem small, it represents many lives when applied to large populations.
Scientists believe the reduction in advanced cancer cases may be due to the removal of precancerous growths before they had time to turn into cancer.
This shows that screening not only detects cancer early but may also prevent it altogether. The findings are especially encouraging because colorectal cancer often grows slowly, giving doctors a valuable window of time to intervene.
The researchers also looked for possible harms from screening, since procedures like colonoscopy can sometimes cause complications. They found a slight increase in issues such as minor bleeding or blood clots, mainly during the first year when most colonoscopies were performed.
However, these complications were uncommon, and the overall death rate from all causes was the same in all groups. This suggests that the benefits of screening likely outweigh the risks for most people.
The study will continue until 2030 to determine whether screening ultimately reduces deaths from colorectal cancer over the long term. If the trend continues, it could support expanding screening programs in many countries. Early detection could become one of the most powerful tools for preventing this disease.
In reviewing the findings, this research provides strong evidence that both colonoscopy and stool-based tests are effective ways to find colorectal cancer early. The large number of participants and the careful design of the study strengthen its conclusions. However, longer follow-up is needed to confirm whether screening significantly lowers death rates.
The study also highlights the importance of encouraging people to participate in screening programs, since the benefits depend on high participation. Overall, the results offer hope that simple tests could prevent suffering and save many lives by catching cancer before it becomes deadly.
If you care about cancer, please read studies that a low-carb diet could increase overall cancer risk, and vitamin D supplements could strongly reduce cancer death.
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