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CRC risk extends to second- and third-degree relatives

Tue, 09/14/2021 - 14:04
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Having second- or third-degree relatives with colorectal cancer (CRC) increases a person's risk of developing the disease, according to the findings of a study led by researchers from the University at Buffalo and the University of Utah.

The study researchers, ‘Early-onset colorectal cancer risk extends to second- and third-degree relatives’, published in Cancer Epidemiology, reviewed more than 1,500 early-onset colon cancer cases in the Utah Cancer Registry, part of the Utah Population Data Base. They found that first-degree relatives of someone diagnosed with early-onset colorectal cancer are six times more likely to be diagnosed with colorectal cancer before age 50, while second-degree relatives are three times likelier and third-degree relatives 1.56 times likelier.

First-degree relatives are defined as parents, children and siblings, and second-degree relatives aunts, uncles, grandparents, grandchildren, nieces and nephews. First cousins, great-grandparents and great-grandchildren are examples of third-degree relatives.

"Unique Utah resources, including a decades-old National Cancer Institute statewide cancer registry and computerized genealogy data for the majority of the population, made this important collaboration possible," explained Dr Lisa Cannon-Albright, professor and leader of the genetic epidemiology program in the Department of Internal Medicine at the University of Utah School of Medicine. She is also a Huntsman Cancer Institute investigator.

"Our study provides new insight into the magnitude of risk for more distant relatives of colorectal cancer cases, and in particular, for relatives of cases who were diagnosed before age 50," says first author, Dr Heather Ochs-Balcom, associate professor of epidemiology and environmental health in UB's School of Public Health and Health Professions. "This work is important given the rising rates of early-onset colorectal cancer."

The study also found that individuals are at a 2.6-fold higher risk of colorectal cancer at any age if they have a first-degree relative with early-onset colon cancer. The risk is 1.96 and 1.3 times greater for second- and third-degree relatives, respectively. In addition, the risk for all degrees of relatives for early-onset colon cancer is higher than the risk for colon cancer at any age.

The findings suggest that early colonoscopy screening may be beneficial for second-degree relatives and possibly third-degree relatives, in addition to first-degree relatives of individuals diagnosed with colorectal cancer before age 50.

The researchers also point out that relatives may benefit from being more aware of their extended family history and sharing this information with their physician when making cancer screening decisions.