Report in English with a Dutch summary (KCE reports 45A)

KCE reports vol.45 Screening for Colorectal Cancer 37
variations) occurs in about 24% of patients at 20 years of follow up. The earliest
recorded is 10 years after ureterosigmoidostomy 99. The observation that the
mean latent period for the development of adenomas is 19,8 years and for
carcinomas is 25,8 years suggests that the adenoma-carcinoma sequence takes a
mean of six years 100-104. It is uncertain whether the neoplasms arise from the
intestinal or the ureteric epithelium or from the anastomosis itself.
3.2.7 Family history of colorectal cancer
Individuals with a family history of colorectal cancer are at increased risk of
developing colorectal cancer. This risk is greater when associated with early age
of onset or multiple affected relatives105-113. Furthermore, there is increasing
awareness among relatives of patients with colorectal cancer that they may be
at increased risk for this disease and consequently there is rising demand for
targeted screening29, 114.
Family history risk factors for CRC include:
3.2.8 Hereditary high risk
1. One first-degree relative (FDR = parents, siblings and children)
diagnosed before age 60.
2. Two FDR diagnosed at any age.
3. A single FDR diagnosed after age 60 may put patients at a very
slightly increased risk. The U.S. Multisociety Task Force on
Colorectal Cancer recommends starting routine screening at
age 40 for patients with a family history of colorectal cancer in a
single FDR diagnosed over the age of 6055, 56.
4. Individuals who have FDR with adenomatous polyps may be at
increased risk for the development of colorectal cancer115, 116.
When two family members have adenomatous polyps,
regardless of the age of diagnosis, targeted screening is
appropriate. As the age of diagnosis in the FDR decreases, the
risk to the individual compared to the average population
increases.
Certain patients are considered to be at high risk for development of colorectal
cancer. Relevant hereditary conditions include108, 117-119, 113, 47:
1. Familial polyposis coli / familial adenomatous polyposis (FAP) 120,
121, 117 and variants.
2. Non-polyposis hereditary colorectal cancer (NPHCC - Lynch
syndrome) 122-125.
Additional syndromes continue to be defined as new genes are linked to the
development of colonic polyps and cancer126, 119, 127-129.
3.3 ESTIMATIONS OF RELATIVE (RR) AND ABSOLUTE RISK
(AR)
3.3.1 The Fuchs study, 1994
Most recommendations on targeted screening of patients with a familial history
of CRC are based on the findings of the study by Fuchs 107 et al. that provided
relative risks for colorectal cancer according to number of affected relatives.
This study was conducted in 2 prospective cohort studies (Nurses Health