Screening for colorectal cancer (CRC) by colonoscopy has been in the news recently with the publication of studies highlighting the modest effect of the use of this method on mortality, but also awareness campaigns carried out by celebrities. , as actor Ryan Reynolds.
Modest Benefits of Colonoscopy
At the 2022 Congress of the European Federation of Gastroenterology (30th UEG week), researchers presented the results of the 10-year follow-up of the multicenter randomized trial NorthICC (Northern-European Initiative on Colorectal Cancer). The results showed that a single screening colonoscopy was beneficial, but perhaps not as much as expected (see infographic). 
The study was designed to be based on a real-life population and replicate national CRC screening programs. All people invited for a screening colonoscopy were compared to those who received usual care (i.e. without invitation or screening). The 10-year provisional risk of CRC was 0.98% in the “guest” group, compared to 1.20% in the group receiving usual care (RR 0.82; 95% CI, 0.70-0.93 ). This suggests that 455 people would need to be referred for colonoscopy to prevent 1 case of colorectal cancer (95% CI, 270-1429). The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the group receiving standard care (RR, 0.90; 95% CI, 0.64-1.16).
Experts have raised concerns about the study, including the fact that only 42% of those invited actually had a colonoscopy. A editorial accompanying the publication points out that cohort studies have shown a 40-69% decrease in the incidence of CRC and a 29-88% decrease in mortality risk.  However, the authors note that “cohort studies likely overestimate the true effectiveness of colonoscopy due to the inability to adjust for important factors, such as incomplete adherence to testing and the tendency of healthier people to seek preventive care. The editorialists also suggest that the benefits of colonoscopy screening take time “because the incidence of CRC is initially increased when pre-symptomatic cancers are identified.” They also note that “colonoscopy is very operator-dependent” and that the detection rate of adenomas varies and affects cancer risk and associated mortality.
Targeted screening by age
A another recent study showed that, in people who do not have an adenoma detected during a reference colonoscopy, the risk of developing advanced neoplasia and CRC is lower in individuals aged 40 to 49 years than in those of 50 to 59 years old.  However, no difference was found between the two age groups in the detection rates of non-advanced adenomas or advanced adenomas. The study involved 2396 people aged 40 to 49 and 8978 aged 50 to 59. A screening colonoscopy was performed in 40.2% of the youngest group versus 34.8% of the oldest group; it was triggered by a positive fecal immunoassay result in 3.3% of the youngest group versus 32% of the oldest group.
The authors found that “comparing the 40-49 year old group to the 50-59 year old group, index colonoscopy did not detect an adenoma in 62.9% of cases versus 40.1% ( P < 0.0001), non-advanced adenomas in 25.4% of cases versus 39.0% (P < 0.001) and advanced adenomas in 11.6% of cases versus 21.0% (P < 0.0001), respectively”. When the two age groups were compared for surveillance colonoscopy, no adenomas were detected in 67% of the younger group versus 54.7% of the older group (P < 0.0001), while non-advanced adenomas were detected in 25.4% versus 38.4%, respectively (P<0.0001), and advanced adenoma was detected in 3.5% versus 6.95% (P<0.0001) , respectively.
Advanced neoplasia was detected at surveillance colonoscopy after baseline colonoscopy in 2.2% of the youngest group and 4.4% of the oldest group (P = 0.0003). At surveillance colonoscopy, non-advanced adenomas were detected in 4.6% vs 7% (P = 0.03), respectively. And advanced adenomas were found in 7.9% in the youngest against 11.7% in the oldest (P = 0.06).
Film actors mobilize
To highlight the importance of colorectal cancer screening, actors Ryan Reynolds and Rob McElhenney recently raised awareness with humor. The two stars filmed their own colonoscopy for the campaign Lead From Behind “. Both actors are now 45, which is the age at which many organizations recommend men at average risk have their first colonoscopy. During the procedure with Ryan Reynolds, doctors identified and removed a polyp that could have seriously evolved over time. Rob McElhenny’s doctor meanwhile found three polyps and removed them as well. These results helped demonstrate the importance of CRC screening in younger men at average risk.
Patients prefer immunological screening test
The preference of young patients for certain types of CRC screening is “alarming” for some experts. Prof. David A. Johnson (Head of Gastroenterology, Eastern Virginia Medical School, Norfolk, USA) recently made part of his concern concerning a study made in California.  In an online survey, 1,000 people were asked about their preferences among the five CRC screening tests recommended by the US Multi-Society Task Force (US-MSTF). The results showed that the preference was consistent for the faecal immunoassay (FIT)/faecal multi-target DNA test in all patients. In a comparison of US-MSTF Level 1 screening tests, the annual FIT test was preferred by 68.9% of people aged 40 to 49 and 77.4% of those aged 50 or older, against only 31.1% and 22.6% for colonoscopy, respectively. Professor Johnson is concerned about this result because “FIT misses 95% of advanced lesions for sessile serrated polyps. When we talk about a detection rate of 5%, it falls under the element of chance. »
Adenoma detection rate among endoscopists
What happens after screening with the immunological test (FIT) would also be of concern. A new study showed that targets for adenoma detection rates by endoscopists performing colonoscopy after a positive immunoassay result should be significantly higher than targets used for primary colonoscopy. The adenoma detection rate is an essential quality indicator because it reflects the ability to detect lesions and is inversely associated with the risk of postcolonoscopy CRC (PCRC). Adults with a positive immunoassay result have a high prevalence of adenomas, resulting in high adenoma detection rates for endoscopists performing colonoscopies.
The study involved 362 accredited endoscopists who performed 116,360 colonoscopies. During a median follow-up of 52 months, 209 interval CCRPs were identified. Endoscopists’ adenoma detection rates ranged from 40% to 82%, with a median rate of 67%. A higher rate was strongly associated with a lower incidence of interval CCRPC, with an adjusted hazard ratio of 0.95 (95% CI, 0.92-0.97) per 1% increase in detection rate adenomas. For endoscopists with a rate of 60%, the cumulative incidence of interval CCRPC was almost twice as high as that of endoscopists with a rate of 7%. For every 1000 colonoscopies performed after a positive immunologic test, the expected number of patients diagnosed with interval CCRP in 5 years was approximately 2 for endoscopists with a rate of 70%, compared to nearly 3.5 for rates of 60% and more than 4.5 for rates of 55%.
Impact of AI on colonoscopy monitoring
Another concern: the use of artificial intelligence (AI) during colonoscopy could increase the burden on patients by increasing the frequency of colonoscopies and the resulting health costs. A new study  showed that the combination of colonoscopy and IA (compared to colonoscopy alone) increased the proportion of patients requiring intensive monitoring by colonoscopy after polypectomy by approximately 35% in the United States and Japan, and by approximately 20% in Europe. The study involved 5796 patients: 2894 underwent AI-assisted colonoscopy and 2902 underwent standard colonoscopy without AI assistance. In all trials, higher adenoma detection rates were observed in the AI-assisted colonoscopy groups.
When the US and Japanese recommendations were followed, the proportion of patients referred for intensive monitoring decreased from 8.4% (95% CI, 7.4%-9.5%) in the no-AI group to 11.% ( 95% CI, 10.2%-12.6%) in the group with IA. When European guidelines were followed, the increase went from 6.1% (95% CI, 5.3%-7.0%) to 7.4% (95% CI, 6.5%-8.4 %). The researchers suggest that these increases are mainly due to the reclassification of patients from the “low risk” category to that of “intermediate or high risk”. This change is likely due to the increased detections of adenomas by AI-related colonoscopy. This can lead to more effective cancer prevention, but also to a potential increase in care and costs.
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