Using cancer registry data, researchers in France estimated the lifetime risk of colorectal cancer among the general population, over a five-year period. They also calculated the risk among first-degree relatives of patients with sporadic colorectal cancer or pre-cancerous lesions.
They found that 1 in 23 men and 1 in 40 women will develop a colorectal cancer during their lifetime.
Lifetime risk of colorectal cancer in France:
Men 1 in 23
Women 1 in 40.
This risk rapidly increased with age and degree of family history of colorectal cancer. At age 74, the risk varied between 8% (with one family member affected) and 26% (with two affected) in men, and 4% and 14% respectively in women.
These findings, alongside results from previous studies, suggest that screening in the general population should start at 50 or 55, say the authors.
For relatives of patients with a colorectal cancer before the age of 45, or for those with at least two affected family members, the lifetime risk is high enough (over 10%) to recommend screening after age 40, they conclude.