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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...

Most data relate to PJS with double-balloon enteroscopy as the preferred method for endoscopy of the small bowel.[369] This may involve only peroral enteroscopy, although subsequent retrograde enteroscopy has been described for more complete evaluation of the total small bowel. Because these procedures are time-consuming and involve some risk of complication, deep enteroscopy is usually preceded by more noninvasive imaging, including traditional barium exams, capsule endoscopy, and CT or magnetic resonance enterography.[72]

In FAP, data from capsule endoscopy [72] show a 50% to 100% prevalence of jejunal and/or ileal polyps in patients with Spigelman stage III or stage IV duodenal involvement, but virtually no such polyps in Spigelman stage I or stage II disease. All polyps were smaller than 10 mm and were not biopsied or removed. Consequently, their clinical significance remains uncertain but is likely limited, given the infrequency of jejunoileal cancer reports in FAP.

Capsule endoscopy in the small series of PJS patients described above [72] showed the presence of a similar frequency (50%–100%) of polyps, but the prevalent polyps were much larger than in FAP, were more likely to become symptomatic, and warranted endoscopic or surgical excision. Capsule studies were suggested as an appropriate replacement for radiographic studies because of the sensitivity of capsule.

Familial CRC

An estimated 7% to 10% of people have a first-degree relative with CRC,[370,371] and approximately twice that many have either a first-degree or a second-degree relative with CRC.[371,372] A simple family history of CRC (defined as one or more close relatives with CRC in the absence of a known hereditary colon cancer) confers a twofold to sixfold increase in risk. The risk associated with family history varies greatly according to the age of onset of CRC in the family members, the number of affected relatives, the closeness of the genetic relationship (e.g., first-degree relatives), and whether cancers have occurred across generations.[370,373] A positive family history of CRC appears to increase the risk of CRC earlier in life such that at age 45 years, the annual incidence is more than three times higher than that in average-risk people; at age 70 years, the risk is similar to that in average-risk individuals.[370] The incidence in a 35- to 40-year-old is about the same as that of an average-risk person at age 50 years. There is no evidence to suggest that CRC in people with one affected first-degree relative is more likely to be proximal or is more rapidly progressive.

A personal history of adenomatous polyps confers a 15% to 20% risk of subsequently developing polyps [374] and increases the risk of CRC in relatives.[375] The RR of CRC, adjusted for the year of birth and sex, was 1.78 (95% CI, 1.18–2.67) for the parents and siblings of the patients with adenomas as compared with the spouse controls. The RR for siblings of patients in whom adenomas were diagnosed before age 60 years was 2.59 (95% CI, 1.46–4.58), compared with the siblings of patients who were 60 years or older at the time of diagnosis and after adjustment for the sibling's year of birth and sex, with a parental history of CRC.


WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
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