All relatives of patients with colorectal cancer are at increased risk for this cancer, regardless of the age at diagnosis of the index patient in the family, according to a study published in Clinical Gastroenterology and Hepatology (2015; doi:10.1016/j.cgh.2015.06.040). These findings may impact future guidance regarding colorectal cancer screening.

“Most surprising, we identified a more than two-fold increase in risk of colorectal cancer among young first-degree relatives (younger than 50 years) of patients with colorectal cancer at advanced ages (60 to 80 years),” said lead study author N. Jewel Samadder, MSc, MD, from Huntsman Cancer Institute at the University of Utah in Salt Lake City. “This risk is not currently appreciated. Increased awareness of this risk may serve as incentive to increase screening intensity for all patients with a first-degree family history of colorectal cancer.”

The researchers conducted a population-based case-control study in Utah identifying 18,208 index patients from the Utah Cancer Registry with colorectal cancer diagnosed between 1980 and 2010; age- and sex-matched cancer-free persons were selected to form the comparison group.

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Increased risk was observed in all relatives regardless of age at the family member’s cancer diagnosis, although the risk was greatest for young relatives (younger than 50 years) of people whose colorectal cancer was diagnosed before age 40 years. However, familial risk was increased in first-degree relatives even when the index case was a cancer diagnosis at an advanced age (older than 80 years).

These findings support the current screening guidelines for patients with a family history of colorectal cancer, primarily more aggressive screening for first-degree relatives of persons with colorectal cancer diagnosis at younger than 60 years. However, because diagnosis even in an older patient can be a predictor of higher risk for colorectal cancer in their relatives, relatives might benefit from knowing this moderate risk and thus avoid known modifiable risk factors and consider preventive measures.

Colorectal cancer is the fourth most common cancer in the United States and is the second leading cause of cancer-related mortality. Heritability is one of the strongest risk factors for colorectal cancer.