Increased Colon and Rectal Cancer Risk Extends to Third-Degree Relatives

For early detection, cancer screening recommendations may be affected by new research finding that even third-degree relatives of people with early-onset colorectal cancer (before age 50) have an elevated risk of the disease.

Patients with early-onset colorectal cancer were found to have first-degree relatives whose risk of developing cancer before age 50 was 6 times higher than in the general population. This risk increase among second- and third-degree relatives was 1.5 times greater.

Family history is a known risk factor for colon and rectal cancer

Colorectal cancer is the 3rd most common cancer both worldwide and in Turkey, and according to Global Cancer Statistics, 1.93 million people were diagnosed with colorectal cancer in 2020. One in every 10 colorectal cancers occurs before age 50, corresponding to approximately 200 thousand people annually.

Before this study, it was unclear how much having relatives with early-onset colorectal cancer contributed to risk beyond familial cancer syndromes, or whether the risk extended beyond first-degree relatives.

The researchers suggest that the new findings mean "taking an extended family history should be part of the discussion when making cancer screening decisions". Their study appeared in the journal Cancer Epidemiology in the August issue.

The authors used the Utah Population Database to examine genealogies linked to the Utah Cancer Registry over more than three generations. The analysis included all colorectal cancer cases with linked genealogical data.

Among 1510 early-onset colorectal cancer cases identified, the team found colorectal cancer risk in first-, second- and third-degree relatives to be respectively 6, 3.1 and 1.6 times higher than expected based on disease rates. All results were statistically significant.

Currently, unless Lynch syndrome or another genetic condition is identified, no screening guidelines exist for second- or third-degree relatives of people with early-onset colorectal cancer.

The authors suggested that early colonoscopy screening could be considered not only for first-degree relatives but also for second- and possibly third-degree relatives of people with early-onset colorectal cancer, and that their findings "may affect future colorectal cancer screening strategy."

Relatives may benefit from genetic counseling to assess underlying inherited conditions. However, this study provides an important resource for introducing earlier population-based colorectal cancer screening.