Genetics of Colorectal Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Major Genetic Syndromes
Table 8. Clinical Practice Guidelines for Diagnosis and Colon Surveillance of Familial Adenomatous Polyposis (FAP) continued...
In most cases, the clinical polyp burden in the rectum at the time of surgery dictates the type of surgical intervention, namely restorative proctocolectomy with IPAA versus IRA. Patients with a mild phenotype (<1,000 colonic adenomas) and fewer than 20 rectal polyps may be candidates for IRA at the time of prophylactic surgery. In some cases, however, the polyp burden is equivocal, and in such cases, investigators have considered the role of genotype in predicting subsequent outcomes with respect to the rectum. Mutations reported to increase the rectal cancer risk and eventual completion proctectomy after IRA include mutations in exon 15 codon 1250, exon 15 codons 1309 and 1328, and exon 15 mutations between codons 1250 and 1464.[149,140,150,153] In patients who have undergone IPAA, it is important to continue annual surveillance of the ileal pouch because the cumulative risk of developing adenomas in the pouch has been reported to be up to 75% at 15 years.[154,155] Although they are rare, carcinomas have been reported in the ileal pouch and anal transition zone after restorative proctocolectomy in FAP patients. A meta-analysis of quality of life following restorative proctocolectomy and IPAA has suggested that FAP patients do marginally better than inflammatory bowel disease patients in terms of fistula formation, pouchitis, stool frequency, and seepage.
Specific cyclooxygenase II (COX-2) inhibitors such as celecoxib and rofecoxib, or nonspecific COX-2 inhibitors, such as sulindac, have been associated with a decrease in polyp size and number in FAP patients, suggesting a role for chemopreventive agents in the treatment of this disorder. Celecoxib is currently approved by the U.S. Food and Drug Administration as an adjunct to endoscopic surveillance following subtotal colectomy in patients with FAP.[158,159,160] Celecoxib reduced the number of polyps by 28% from baseline, and the sum of the polyp diameters by 30.7% in patients with FAP; however, it is unknown whether this will translate into reductions in CRC incidence or mortality, or improvements in quality of life. Rofecoxib has also been shown to modestly reduce the number of polyps in patients after subtotal colectomy. Rofecoxib (25 mg/day) reduced the number of polyps by 6.8% from baseline in 21 patients after 9 months of treatment.
A small, randomized, placebo-controlled, dose-escalation trial of celecoxib in a pediatric population (aged 10–14 years) demonstrated the safety of celecoxib at all dosing levels when administered over a 3-month period. This study found a dose-dependent reduction in adenomatous polyp burden. At a dose of 16 mg/kg/day (which approximates the approved dose of 400 mg twice daily in adults), the reduction in polyp burden paralleled that demonstrated with celecoxib in adults.