Genetics of Colorectal Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Major Genetic Syndromes
Table 9. Practice Guidelines for Diagnosis and Colon Surveillance of Lynch Syndrome continued...
A common but unproven clinical practice is to initiate CRC screening 10 years before the age of the youngest CRC case in the family. There is neither direct evidence nor a strong rational argument for using aggressive screening methods simply because of a modest family history of CRC.
These issues were weighed by a panel of experts convened by the American Gastroenterological Association before publishing clinical guidelines for CRC screening, including those for persons with a positive family history of CRC. These guidelines have been endorsed by a number of other organizations.
The American Cancer Society and the United States Multi-Society Task Force on Colorectal Cancer have published guidelines for average-risk individuals.[130,393,394,395,396] These guidelines address screening issues related to modest family history of CRC or adenomas. Given the heterogeneity of this grouping, it is beyond the scope of this more targeted discussion of major gene conditions.
Rare Colon Cancer Syndromes
Peutz-Jeghers syndrome (PJS)
PJS is an early-onset autosomal dominant disorder characterized by melanocytic macules on the lips, and the perioral and buccal regions, and multiple gastrointestinal polyps, both hamartomatous and adenomatous.[397,398,399] Germline mutations in the STK11 gene at chromosome 19p13.3 have been identified in the vast majority of PJS families.[400,401,402,403,404] (Refer to the Peutz-Jeghers Gene(s) section in the PDQ summary on Genetics of Colorectal Cancer for more information.) The most common cancers in PJS are gastrointestinal. However, other organs are at increased risk of developing malignancy. A systematic review found a lifetime cumulative cancer risk, all sites combined, of up to 93% in patients with PJS.Table 10 shows the cumulative risk of these tumors. The high cumulative risk of cancers in PJS has led to the various screening recommendations summarized in the table of Clinical Practice Guidelines for the Diagnosis of Cancer in Peutz-Jeghers Syndrome in the PDQ summary on Genetics of Colorectal Cancer.
Although the risk of malignancy appears to be exceedingly high in individuals with PJS based on the published literature, the possibility that selection and referral biases have resulted in over-estimates of these risks should be considered.
Table 10. Cumulative Cancer Risks in Peutz-Jeghers Syndrome Up To Specified Agea
|Site||Age (y)||Cumulative Risk (%)b||Reference(s)|
|GI = Gastrointestinal.|
|a Reprinted with permission from Macmillan Publishers Ltd:Gastroenterology, copyright 2010.|
|b All cumulative risks were increased compared to the general population (P< .05) with the exception of cervix and testes.|
|c GI cancers include colorectal, small intestinal, gastric, esophageal, and pancreatic.|
|d Westerman et al.: GI cancer does not include pancreatic cancer.|
|e Did not include adenoma malignum of the cervix or Sertoli cell tumors of the testes.|
|Per origin|| || || |