Objective: This study aims to examine colonic polyp phenotype, the surgical outcomes, and the reasons for colectomy in individuals with attenuated familial adenomatous polyposis (AFAP).
Methods: Colonoscopy and colectomy medical records were obtained for 197 individuals with a known genetic mutation in the region of the APC gene causative of AFAP.
Results: The number of adenomas was highly variable for both individuals being screened by colonoscopy and those having had a colectomy. The probability of an AFAP patient in this cohort having a colectomy is only 20% at age 40, however, after this age, the probability climbs dramatically. The average age of colectomy is 52 years. By age 70, the cumulative probability of having a colectomy is approximately 80% in this AFAP population. When the population was broken into 5 equal sized birth cohorts (Figure1), we see a trend whereby colectomies are being performed at younger ages in the most recent cohorts (p=0.0001). The major reason for colectomy is a high number or polyps (Figure 1).
Discussion: Colectomy appears to becoming more common in patients with AFAP and is being recommended at younger ages. A greater number of colectomies were performed in the 1990s which coincided with the identification of the APC gene mutation in this family. Subtotal colectomy with ileorectal anastomosis (IRA) is the most common type of colectomy, though 23% still had proctocolectomies with ileoanal anastomosis. Cancer risk did not necessarily correlate with polyp number as 7 individuals with fewer than 20 polyps developed cancer. In the end several factors should be considered in developing a management plan for individuals with AFAP, including lifestyle, polyp number, comorbidities, adherence to screening and patient attitudes.