___________________________________________________________________________ Colorectal Cancer
brain tumors (particularly medulloblastoma) [91; 97; 104]. The lifetime risk of extracolonic tumor development in FAP is [90]: • Desmoid: 15% • Duodenum: 5% to 12% • Thyroid: 2% • Brain: 2%
cancer is eventual colectomy. In patients with early-stage classic FAP, the surgeon, endoscopist, and patient/family may opt to delay surgery for several years in the interest of achieving social milestones [90]. Carefully selected patients with attenuated FAP who show minimal polyp burden and are of advanced age may also defer decision-making about colectomy [112]. The timing of risk-reducing surgery is based on symptomatol- ogy and the number, size, and histology of polyps. Surveil- lance colonoscopy is not useful after numerous polyps have developed, because it is no longer possible to remove and biopsy all of them. It is appropriate for patients at this time to consult with a surgeon experienced with available options, including total colectomy and postcolectomy reconstruction techniques. Rectum-sparing surgery followed by sigmoido- scopic surveillance of the remaining rectum is an option for patients who wish to avoid total colectomy, provided they are able to understand the risks and consequences and to follow through with surveillance recommendations [112]. Familial Colorectal Cancer Many families exhibit aggregation of colorectal cancer and/ or adenomas in the absence of known or identifiable genetic susceptibility factors; this is termed familial colorectal cancer [114]. The presence of colorectal cancer in more than one family member may be caused by hereditary factors, shared environmental risk factors, or even chance. Familial colorectal cancer accounts for 20% of all colorectal cancer cases [115]. In the general population, 7% to 10% of individuals have a first-degree relative with colorectal cancer and 14% to 20% have either a first-degree or a second-degree relative with colorectal cancer [91; 97; 104]. A simple family history of colorectal cancer (i.e., colorectal cancer in one or more close relatives, known hereditary colon cancer absent) confers a two- to six-fold increase in risk, with degree of risk influenced by family member’s age of colorectal cancer onset, the number of affected relatives, closeness of the genetic relationship, and whether colorectal cancer has occurred across generations. A positive family history of colorectal cancer appears to increase the risk of colorectal cancer earlier in life such that at 45 years of age, the annual incidence is more than three times higher than in average-risk people; at age 70 years, the risk is similar to that in average-risk individuals [116]. The incidence in individuals 35 to 40 years of age is about the same as that of an average-risk person at 50 years of age. There is no evidence to suggest that colorectal cancer in people with one affected first-degree relative is more likely to be proximal or more rapidly progressive [91; 97; 104]. Although controlled comparisons have not been performed of genetic screening in persons with modest family history of colorectal cancer, expert opinion is fairly consistent that colorectal cancer screening should begin earlier in life (35 to 40 years of age, when risk magnitude approximates that of an individual 50 years of age) [116]. Screening in persons with average risk of colorectal cancer should begin at 50 years of
• Ampullary: 1.7% • Pancreas: 1.7% • Hepatoblastoma: 1.6% • Gastric: 0.6%
Diagnosis . The clinical diagnostic criteria of FAP is a patient with 10 to 99 adenomatous colon polyps diagnosed by 40 years of age, or more than 100 polyps diagnosed at an older age than expected [90]. Surveillance . The recommended age at which surveillance for polyposis should begin involves a trade-off. On one hand, a patient who waits until the late teens to begin surveillance faces a remote possibility that a cancer will have developed at an earlier age. Although it is rare, colorectal cancer can develop in a teenager who carries an APC mutation. On the other hand, it is preferable to allow people at risk to develop emotionally before they are faced with a major surgical decision regarding the timing of colectomy. Therefore, surveillance is usually begun in the early teenage years (10 to 15 years of age) [112]. Surveillance has consisted of either flexible sigmoidoscopy or colonoscopy (preferred) every year. If flexible sigmoidoscopy is utilized and polyps are found, colonoscopy should be per- formed. Historically, sigmoidoscopy may have been a reason- able approach at the time in identifying early adenomas in a majority of the patients [113]. However, colonoscopy should be considered the tool of choice in light of improved instru- mentation for full colonoscopy, safer and deeper sedation (with propofol), recognition that malignancy is more common in the right colon with attenuated FAP, and the growing tendency to defer surgery for a number of years [90]. Individuals test- ing negative for an otherwise known family mutation do not need FAP-oriented surveillance and can undergo average-risk population screening. In the case of families where no family mutation has been identified in an affected person, clinical surveillance is warranted [90; 91; 97; 104]. Colon surveillance should not be stopped in carriers of an APC mutation who do not yet manifest polyps, because adenomas occasionally do not appear before the fourth and fifth decades of life. In some circumstances, full colonoscopy is preferred over the more limited sigmoidoscopy. Tolerability of endo- scopic procedures among pediatric patients has improved with the use of deeper intravenous sedation [91; 97; 104]. Interventions . After an APC mutation is identified in a patient or member of their family, evaluation for polyposis by flexible sigmoidoscopy or colonoscopy begins promptly. In those show- ing polyps, the only effective management to prevent colorectal
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