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Risk-adapted starting ages proposed for colorectal cancer screening in diabetics

PLoS Medicine
Reuters Health - 13/11/2020 – New evidence based on registry data suggests that in diabetic patients, colorectal cancer (CRC) screening should be initiated based on age, sex and family history.

"Our study shows that diabetic patients should undergo colorectal cancer screening about five years earlier than the general population, as the incidence of colorectal cancer in young adults is increasing," Dr. Mahdi Fallah of the National Center for Tumor Diseases in Heidelberg told Reuters Health by email.

Although more research is definitely warranted, he said "one may not (want to) wait until more lengthy (studies) are completed. We would recommend taking advantage of this available information right now, especially in the context that some cancer societies, like the American Cancer Society, have issued a qualified recommendation for the general population to start colorectal cancer screening at age 45." (https://bit.ly/38Epa21)

Individuals with diabetes and a family history of colorectal cancer "should start screening 12 to 21 years earlier than the general population, depending on sex and the benchmark starting age of mass screening in the general population," he suggested. "For example, in countries where mass screening starts at age 50, men with both diabetes and family history should start screening at age 32 and women, at age 38."

When starting ages differ for those with diabetes and those with a family history of colorectal cancer regardless of diabetes (https://bit.ly/2MORKSq), "whichever is earlier should be followed," he said.

As reported in PLoS Medicine, for each single age, the team calculated the risk of developing CRC in the next 10 years. For example, at age 50, which is the most common age for starting CRC screening, the risk in the Swedish population was 0.44% in men and 0.41% in women.

Diabetic patients reached the screening level of CRC risk earlier than the general population – i.e., men with diabetes reached 0.44% risk at age 45 (five years earlier than the recommended starting age), whereas for women with diabetes, the risk advancement was four years.

As Dr. Fallah noted, risk was more pronounced for those who also had a family history of CRC (12–21 years earlier depending on sex and benchmark starting age of screening).

Study limitations include lack of detailed information on diabetes type, lifestyle factors, and colonoscopy data.

Dr. Fallah added, "A particular finding of this study, which is prone to be ignored, is that screening in those without diabetes and without family history of colorectal cancer, who are the majority of population, can be delayed one year – e.g., starting from age 51 instead of 50 - which would compensate the cost and burden of earlier screening in the high-risk minority with early-onset diabetes and/or family history of colorectal cancer."

Dr Ajay Rao, Associate Professor in the Center for Metabolic Disease Research at the Lewis Katz School of Medicine at Temple University in Philadelphia, called the findings "very interesting." However, he told Reuters Health by email, "there is a need for (additional) studies to investigate these results further. It would be most important to determine whether this signal is present in other populations outside of Sweden."

"There are some major limitations, including lack of robust detailed data on lifestyle factors, which may be important information for both diabetes and colorectal cancer risk," he noted. For example, "obesity may be a common risk factor for both diabetes and cancer that must be also brought into the discussion in any study connecting cancer risk with diabetes."

"I would be concerned about adoption by clinicians before there are studies done in other populations outside of Sweden to replicate the findings and without major organizations reappraising guideline recommendations in light of these findings," he said.

"If these results (can) be replicated in other populations, it would be crucial for major organizations to reconsider colorectal cancer screening practices to determine if individuals living with diabetes should be screened earlier than others," he concluded.

By Marilynn Larkin

SOURCE: https://bit.ly/2IAkaRj PLoS Medicine, online November 13, 2020.

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