At what age is a second-degree relative's (family member) diagnosis of colon cancer considered a significant risk factor for earlier screening?

From the Guidelines

A second-degree relative's diagnosis of colon cancer at any age is considered a significant risk factor, and screening should begin at age 45 or 10 years before the youngest diagnosis in the family, whichever comes first, according to the most recent guidelines 1. When considering the risk of colon cancer based on family history, it's essential to understand the degree of relationship and the age at diagnosis.

• A second-degree relative, such as a grandparent, aunt, uncle, niece, nephew, or half-sibling, diagnosed with colon cancer at any age increases the risk.
• The National Comprehensive Cancer Network guidelines from 2022 recommend colonoscopy every 10 years or per colonoscopy findings beginning at age 45 for individuals with a second-degree relative diagnosed with colon cancer at any age 1.
• The American Gastroenterological Association's clinical practice update on risk stratification for colorectal cancer screening also supports earlier screening for individuals with a family history of colon cancer, including second-degree relatives 2.
• The key factor is the increased genetic risk associated with a family history of colon cancer, particularly when the relative is diagnosed at a younger age.
• Early screening allows for the detection and removal of precancerous polyps, significantly reducing the risk of developing colorectal cancer.
• It's crucial to note that the guidelines may vary, but the most recent and highest-quality studies support earlier screening for individuals with a family history of colon cancer, including second-degree relatives 1, 2.

From the Research

Second-Degree Relatives and Colorectal Cancer Screening

• A second-degree relative's diagnosis of colon cancer is considered a significant risk factor for earlier screening, although the exact age is not explicitly stated in the provided studies 3, 4, 5, 6, 7.
• The studies primarily focus on the risk associated with first-degree relatives, with recommendations for screening starting at age 40 or 10 years before the age of diagnosis of the youngest affected relative, whichever is earlier 3, 4.
• For individuals with a family history of nonhereditary colorectal cancer or adenoma, the Canadian Association of Gastroenterology Banff Consensus suggests that those with an first-degree relative with CRC or documented advanced adenoma should initiate screening at a younger age (e.g., 40-50 years or 10 years younger than age of diagnosis of first-degree relative) 7.
• However, for second-degree relatives, it is suggested that individuals with a family history of ≥1 second-degree relatives only, or of nonadvanced adenoma or polyp of unknown histology, be screened according to average-risk guidelines, which typically start at age 50 7.
• There is limited information on the specific age for screening in second-degree relatives, and more research is needed to provide definitive evidence-based recommendations 6, 7.