Colorectal Cancer
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Colonoscopy screening intervals could be extended for people without a family history of colorectal cancer (CRC), research suggests, allowing them to avoid unnecessary invasive examinations.

The decade-long interval between screenings could potentially be extended to 15 years for those whose first colonoscopy is negative for the cancer, without resulting in major adverse consequences.

The study, published in JAMA Oncology, adds to an evolving body of evidence that supports extending the historical 10-year screening interval for individuals at average CRC risk.

‘This study provides evidence for recommending a longer colonoscopy screening interval than what is currently recommended in most guidelines for populations with no familial risk of CRC,” report Mahdi Fallah, PhD, from the German Cancer Research Center in Heidelberg, and colleagues.

CRC is the third most common cancer and second most common cause of cancer deaths in the world.

Most colorectal cancer screening guidelines currently endorse a 10-year interval a colonoscopy with no abnormal findings, based on a consensus on the time frame for a benign tumor to transform into carcinoma.

Noting that emerging evidence suggests this could be extended, the researchers studied the world’s largest complete nationwide family cancer dataset.

Specifically, the team studied information on more than 110,000 people in Sweden with no family history of CRC and negative results on their first colonoscopy at age 45 to 69 years.

A negative finding was defined as a first colonoscopy without a diagnosis of colorectal polyp, adenoma, carcinoma in situ, or colorectal cancer before or within 6 months after screening.

These participants were compared with nearly two million matched control individuals who either did not have a colonoscopy during the follow-up or underwent colonoscopy that resulted in a CRC diagnosis.

During a maximum of 29 years of follow-up, there were 484 incident cases of CRC and 112 CRC deaths among the group with negative colonoscopy findings, compared with figures of 21,778 CRC cases and 552 CRC deaths in the control group.

Up to 15 years after a first colonoscopy that had negative results, the risks of CRC and CRC death remained lower than among control individuals.

The 10-year cumulative risk of CRC by year 15 among participants with a first negative colonoscopy was 72% that of control individuals. For death from CRC, the 10-year cumulative risk was 55% that of the control group.

Extending the screening interval from 10 to 15 years would miss only an estimated 2.4 additional CRC cases and 1.4 additional CRC deaths per 1000 individuals would occur, while potentially avoiding one colonoscopy per lifetime for each individual.

Increasing the screening interval from 15 to 16 years, or even 20 years, did not avoid colonoscopies. In addition, it had the potential to increase harm, with missed invasive CRC cases rising from 2 to 4–12 cases per 1000 individuals, and CRC-specific deaths rising from 1 to 2–4 deaths per 1000 individuals.

In an accompanying Comment article, Rashid Lui and Andrew Chan, PhD, both from the Chinese University of Hong Kong, say the findings question the “magic number” of 10 years.

“Taken together, these data suggest that 15 years may be the optimal screening interval after a colonoscopy with negative results,” they write.

However, Lui and Chan note that the study based on data collected in European populations.

“Validation of these results in other settings is critical to generalize these findings globally, including parts of the world, such as Asia, in which widespread CRC screening has begun more recently,” they maintain.

“Not only is it possible that the timing of the adenoma-carcinoma sequence may differ in non-European populations, but variation in the background incidence of CRC will significantly impact the number of incident CRCs prevented associated with a given screening interval.”

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