Colorectal cancer patients should be screened for environmental and genetic factors, suggests a new study based on 9,748 colorectal cancer cases, both the factors were termed as E- factor and G- factor, respectively.

A new risk-prediction model, built by researchers at the University of Michigan and the Fred Hutchinson Cancer Research Center (Fred Hutch) in Seattle and colleagues, assesses the impact of environment and genetic factors on the development of colorectal cancer.

The researchers calculated the combined risk from 19 lifestyle and environmental factors and 63 genetic variants associated with colorectal cancer. Current guidelines recommended initial screening at age 50 unless someone has a history of colorectal cancer.

"Our model could provide a much wider range for the first colorectal cancer screening," said Jihyoun Jeon, an assistant research scientist in epidemiology at the UM School of Public Health and the first author of this article's Gastroenterology.

Jeon said when factoring in environmental (E-score), and genetic factors (G-score) with family history risk, the suggested starting ages for screening were different by the span of as many as 12 years for men and 14 for women, depending on where people landed in the risk profile.

For example, she said, among people with a family history of colorectal cancer, men in the highest 10% of risk were recommended for screening at age 40, while those in the lowest 10% could wait until age 51. For women, the ages were 46 and 59.

For those with no family history but with environmental risk exposure and genetic profile that put them in the highest risk the ages for the first screening were 44 for men and 50 for women; for the lowest risk, 56 and 64.

The researchers found that environmental factors and genetics impacted risk are equally important, showing that both aspects when making decisions about colorectal cancer screening is important.

The researchers say employing their model is a next step forward in the path to precision medicine, but they acknowledge that this information is not available for patients in clinical settings.

"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," Jeon said.

Her colleagues agreed, saying they hope their research prompts patients and doctors to discuss known lifestyle and environmental factors such as height, body mass index, education, history of type 2 diabetes, smoking, alcohol, diet, use of various pharmaceuticals and physical activity.

The team collected data from 9,748 colorectal cancer cases and 10,590 controls in the Genetics and Epidemiology and Colorectal Cancer Consortium and the Colorectal Transdisciplinary Study from 1992 to 2005.

Due to insufficient samples of other ancestry groups, only individuals of European descent were included in the study. The team plans to do additional research on more diverse subjects.

"As we are we are going to have all kinds of diseases," said Li Hsu, member of biostatistics at Fred Hutch. "The genetic information that has to be used for colorectal cancer but can be readily available for many other genetic bases. "