Risk of rectal cancer in patients after colectomy and ileorectal anastomosis for familial adenomatous polyposis: a function of available surgical options.
PURPOSE: One of the concerns with colectomy and ileorectal anastomosis as a prophylactic procedure for patients with familial adenomatous polyposis is the risk of metachronous rectal cancer, estimated at from 12 to 43 percent. These estimates are based largely on surgeries performed at a time when the only alternative option to ileorectal anastomosis for patients with severe familial adenomatous polyposis was proctocolectomy and ileostomy. This study was designed to test the hypothesis that in the pouch era severe polyposis is now treated by proctocolectomy and ileal pouch-anal anastomosis. Ileorectal anastomosis is performed mostly in mildly affected patients and will therefore carry a very low risk of metachronous rectal cancer. METHODS: Patients undergoing primary prophylactic surgery for familial adenomatous polyposis between 1950 and 1999 were categorized according to the year of their surgery: prepouch era (before 1983) or pouch era (after 1983). Patients undergoing colectomy and ileorectal anastomosis were the focus of the study, and rate of proctectomy and the incidence of rectal cancer were recorded for each group. Data on the severity of the polyposis for each group were abstracted. RESULTS: A total of 197 patients underwent ileorectal anastomosis, 62 in the prepouch era (median follow-up, 212 months; interquartile range, 148 months) and 135 in the pouch era (median follow-up, 60 months; interquartile range, 80 months). Patients in the prepouch era came to surgery at the same median age as those in the pouch era (median age 23.0 years, interquartile ranges 15.5 years for prepouch and 17 years for pouch). Similar proportions of patients in the prepouch era had severe polyposis (49 percent) as in the pouch era (44 percent), although all severely affected patients had an ileorectal anastomosis in the prepouch era vs. 39 percent in the pouch era. Twenty (32 percent) prepouch-era patients underwent proctectomy compared with three (2 percent) pouch-era patients. No pouch-era patient had rectal cancer on follow-up; eight (12.9 percent) prepouch-era patients did. CONCLUSION: Although follow-up is shorter, ileorectal anastomosis for familial adenomatous polyposis performed since 1983 carries a much lower rate of rectal cancer and proctectomy than ileorectal anastomosis performed before this time, when restorative proctocolectomy was not an option. This is related, at least in part, to a greater number of patients with severe polyposis having their rectum initially spared.