Colorectal Cancer Screening Should Consider Environmental, Genetic Factors

Standard colorectal cancer screening guidelines may not accurately assess risks in certain patients.

Standardized cancer screening guidelines were created to ensure that individuals of similar risk levels are receiving proper preventive care.

For colorectal cancer (CRC), individuals may benefit from personalized screening recommendations opposed to standardized guidelines, a study published by Gastroenterology suggests. Current recommendations advise screening to start at age 50 years unless there is a family history of CRC.

A recently created risk prediction model developed by the study authors may be able to better account for the effect of environmental and genetic factors on colorectal cancer risk.

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The model calculates risk based on 19 lifestyle and environmental factors and 63 genetic factors linked to CRC. When developing the model, the researchers collected data from 9748 cases of CRC and 10,590 controls from 1992 to 2005.

"Our model could provide a much wider age range for the first colorectal cancer screening," said first author Jihyoun Jeon, PhD, MS.

By accounting for environmental (E-score) and genetic (G-score) factors, in addition to family history, the authors found that the starting age for CRC screening differed from current recommendations up to 12 years for men and 14 years for women. The variations were dependent upon a patient’s individual risk, according to the authors.

For patients with a family history of CRC, men in the highest 10% category were recommended to start screening at age 40 years, while those in the lowest 10% were recommended to wait until age 51 years, according to the study. The model suggested that women in the highest cohort should start screening at age 46 years and those in the lowest should wait until age 59 years.

For patients with no family history and E-score and G-score risks, those with the highest risk were advised to start screening at age 44 years for men and age 50 years for women. Men and women with the lowest risk were advised to start CRC screening at age 56 years and age 44 years, respectively, according to the study.

The novel tool showed that both E- and G-scores affected CRC risk equally, which stresses the importance of considering both factors when developing screening recommendations, the authors stated.

The researchers said that this model could be useful in the push towards precision medicine; however, such information is not widely available in a clinical setting, according to the study.

"Much more work needs to be done but we hope our research provides good evidence that risk prediction models can be used to pinpoint individual risk more precisely," Dr Jeon said.

Since lifestyle and environmental factors—such as height, weight, education, type 2 diabetes, smoking, alcohol use, diet, prescription drugs, and exercise—can significantly impact CRC risk, the authors hope physicians discuss these risks with their patients.

"As we age we are going to have all kinds of diseases," said researcher Li Hsu, PhD. "The genetic information can not only be used for colorectal cancer but can be readily available for many other complex diseases that have a genetic basis."