Major Genetic Syndromes
Table 8. Clinical Practice Guidelines for Diagnosis and Colon Surveillance of Familial Adenomatous Polyposis (FAP) continued...
In other series, the risk of developing adenomas in an MMR gene mutation carrier has been reported to be 3.6 times higher than the risk in noncarriers. By age 60 years, 70% of the carriers developed adenomas, compared with 20% of noncarriers. As previously mentioned, these mutation carriers developed adenomas at an earlier age than noncarriers. Most of the adenomas in carriers had absence of MMR protein expression and were more likely to have dysplastic features, compared with adenomas from control subjects. Given that colonoscopy is the accepted measure for colon cancer surveillance, preliminary data suggest that the use of chromoendoscopy, such as with indigo carmine, may increase the detection of diminutive, histologically advanced adenomas.[327,328]
Although screening the intact colon is usually recommended for at-risk LS family members, some patients, faced with the high risk of CRC and the fallibility of screening, elect to undergo risk-reducing colectomy. However, there is a risk of developing cancer in the remaining rectum.
Level of evidence: 3a
Table 9 summarizes the clinical practice guidelines from different professional societies regarding diagnosis and surveillance for LS.
Table 9. Practice Guidelines for Diagnosis and Colon Surveillance of Lynch Syndrome
|Organization ||Tumor MSI||Tumor IHC||MMR Mutation Testing||Age Screening Initiated||Frequency||Method||Comments|
|C = colonoscopy; GI = gastrointestinal; IHC = immunohistochemistry; MMR = mismatch repair; MSI = microsatellite instability; NA = not addressed; NCCN = National Comprehensive Cancer Network.|
|a GI Societies – American Academy of Family Practice, American College of Gastroenterology, American College of Physicians-American Society of Internal Medicine, American College of Radiology, American Gastroenterological Association, American Society of Colorectal Surgeons, and American Society for Gastrointestinal Endoscopy.|
|American Cancer Society||NA||NA||Counseling to consider genetic testing||21 y||1–2 y until age 40 y, then annually||C|| |
|American Society of Colon and Rectal Surgeons[134,135,136]||Yes||Yes||Yes||NA||NA||NA|| |
|Europe Mallorca Group||Yes||Yes||Yes||20–25 y; consider stopping at age 80 y||1–2 y||C||Despite acknowledging that existing data support a 3 y screening interval, this group elected to recommend a shorter screening interval.|
|GI Societiesa ||NA||NA||NA||20–25 y||1–2 y||C|| |
|NCCN||Yes||Yes||Yes||20–25 y OR 2–5 y prior to the youngest age at diagnosis in the family if it is before age 25 y; whichever comes first||1–2 y||C||Families in whom a tumor has shown informative IHC and MSI, but no germline mutation found, should have at-risk relatives screened as if they were mutation carriers.|