MIT Study Reveals Colonoscopies Twice as Effective as Previously Thought in Preventing Cancer

New findings from the Massachusetts Institute of Technology (MIT) suggest that the life-saving potential of preventive screening colonoscopies is significantly greater than previously thought. MIT researchers discovered that colonoscopy and sigmoidoscopy, the two primary tests for detecting colon cancers and polyps, offer double the protective benefits identified in earlier studies.

In various colon cancer screening trials, it’s typically projected that 1% of participants will develop the disease within the following decade. Past studies have shown that regular colonoscopy or sigmoidoscopy reduces this risk by 25%, bringing the rate down to 0.75%. However, the latest analysis from MIT accounts for those participants who choose not to undergo screening. When these individuals were removed from the statistical analysis, the actual percentage of people who developed colon cancer over a 10-year period dropped to just 0.5%.

Josh Angrist, an econometrician at MIT, emphasizes that the actual act of undergoing screening has a far more substantial impact than previously reported. The results double the benefits highlighted in past research, which mainly focused on the benefits of simply being invited to screen. This reinforces the importance of following through with screening recommendations for colon cancer.

The American Cancer Society currently advises that individuals at average risk for colorectal cancer begin regular screenings at 45 years of age. This can be conducted via a stool-based test, which searches for cancer indicators in feces and should be done annually, or through a visual exam that inspects the colon and rectum, recommended every 10 years. In cases where the noninvasive stool test yields suspicious results, a follow-up colonoscopy is advised.

Angrist and his team analyzed data from five major clinical trials on colon cancer screening. These trials varied in their use of sigmoidoscopy or colonoscopy and showed a wide range of adherence, with 42% to 87% of participants actually undergoing the offered procedures. The MIT group’s adjusted findings for non-adherence showed more than a doubling in the benefit of regular colon cancer screening, smoothing out inconsistencies in the results of the five trials and confirming that screening reduces the odds of developing colon cancer from 1% to 0.5% over the next decade.

Angrist hopes this new data will encourage higher screening rates. He advises that when talking to someone hesitant about colonoscopy, it’s more persuasive to discuss the actual effects of screening rather than the mere invitation to screen. The impact of screening, he points out, is a much more compelling argument. This new evidence holds the potential to save more lives and could be a crucial step in bolstering public health initiatives aimed at preventing colon cancer.


Instrumental variables methods reconcile intention-to-screen effects across pragmatic cancer screening trials. Joshua D. Angrist and Peter Hull