if a relative has colon cancer, you may be at risk

researchers recommend staying updated on the medical history of extended family to increase the likelihood of proper diagnosis.

by dave yasvinski

published sep 15, 2021

last updated sep 14, 2022

3 minute read

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3 minute read

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people with relatives who have colon cancer are at increased risk

extended family may hold clues to your risk of developing cancer. getty

people who have second or third-degree relatives with colorectal cancer are at increased risk of developing the disease themselves, according to researchers who say this group would likely benefit from the type of early screening usually reserved for those with a closer connection. the study, published in the journal cancer epidemiology, found that second-degree relatives of early-onset colorectal cancer patients (such as grandparents, aunts, uncles, nieces and nephews) are three times more likely to be diagnosed with the cancer before the age of 50. third-degree relatives (first cousins, great grandparents, great grandchildren) are 1.56 times likelier to develop the disease.

screening for colorectal cancer before the age of 50 has typically been recommended for first-degree relatives (parents, children and siblings), a group the study found to be six times more likely to be affected by the same diagnosis. “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,” said heather ochs-balcom, first author of the study and an associate professor of epidemiology and environmental health at the university of buffalo’s school of public health and health professions. “this work is important given the rising rates of early-onset colorectal cancer.”

colorectal cancer is the third-most diagnosed cancer in canada, with just under 27,000 new cases arising in 2020, according to cancer.ca. it is the second leading cause of death from cancer in men and third in women. with approximately 73 canadians receiving the dire diagnosis — and another 27 dying from the disease — every day, identifying new causes and interventions have become a priority among researchers.

the team from ub and the university of utah arrived at their conclusions after studying data from more than 1,500 cases of early-onset colon cancers included in the utah cancer registry. “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,” said 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.

the study also found that people with a first-degree relative who have been diagnosed with early-onset colorectal cancer were found to face a 2.6-fold higher risk of developing the disease at any age. the risk is 1.96 and 1.3 times greater, respectively, when dealing with second and third degree relatives. the risk to all degrees of relatives was found to be higher than the typical risk of colon cancer at any age.

previous research in the u.s. has recommended lowering the age of colorectal cancer screening among individuals of average risk from 50 to 45 to account for rising rates of the disease in younger adults. the task force that made the recommendation settled on the age of 45 based on research that showed the five-year head start will prevent more deaths while introducing minimal increases to potential colonoscopy complications. the task force still recommends selectively screening people between the ages of 76 and 85 because more rigorous testing produces relatively small increases to the lifespan of this age group.

the authors of the current study said early screenings would likely be beneficial for second and third-degree relatives. they also recommend that people try to stay updated on the medical history of their extended family and share this information with their family doctor to increase the likelihood of proper diagnosis and treatment of the cancer and any other disease or condition that might require prompt attention.

dave yasvinski is a writer with healthing.ca

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