(ChemotherapyAdvisor) – First-, second- and third-degree relatives of patients with colorectal cancer (CRC) have an increased risk of developing CRC or adenomas themselves, with the strength of the association based on the degree of kinship, the first population-based assessment of such risk reported during the American College of Gastroenterology’s 77th Annual Scientific Meeting in Las Vegas, LV.

“This study has resolved many of the issues confounded in previous studies where reliance on patient recall regarding family history and lack of verification of reported colorectal cancer diagnoses have made it difficult to quantify the risk of CRC in the relatives of patients with colorectal cancer,” said Niloy Jewel Samadder, MD, of the University of Utah and Huntsman Cancer Institute, Salt Lake City, UT, noting that the “biggest strength” of the study is its design.

The retrospective case-control study included 126,936 Utah residents between 50 and 80 years of age who underwent colonoscopy between 1995 and 2009 at Intermountain Healthcare of University of Utah Health System. The case population was defined as the 3,804 patients diagnosed with CRC. Each case was age- and sex-matched with a randomly selected control who did not have CRC, by colonoscopy. The investigators confirmed family relationships through the Utah population database and CRC diagnosis through the Utah Cancer Registry.

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Results showed that first-degree relatives of individuals with CRC had a 79% increased risk for CRC (95% CI, 1.59–2.03); second-degree relatives an increased risk of 32% (95% CI, 1.19–1.47); and third-degree relatives, an increased risk of 15%.”(95% CI, 1.07–1.25). This risk was similar for first-degree relatives whether patients developed CRC below or above the age of 60 years. The prevalence of adenomas was also increased 82% in first-degree relatives, 19% in second-degree relatives, and 10% in third-degree relatives; again, risk was similar regardless of age. No elevated risk for CRC was found in spouses of those with CRC.

“Our data support the current CRC screening guidelines and raise the question of whether such screening should be extended to first-degree relatives of patients with CRC diagnosed at or above age 60,” said Dr. Samadder, adding that the results, “further support a genetic basis of inheritance for CRC over shared environmental factors.”

A key message from the study is that “the risk for colorectal cancer doesn’t stop at our first-degree relatives,” he added, urging patients to be aware of their extended family histories and encouraging physicians to look beyond a patient’s parents and grandparents when assessing colorectal cancer risk.

Abstract (select Oral & Posters, Browse by Number and select Abstract Number 9):