Oral Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2018

Management of Familial Adenomatous Polyposis (FAP) (#6)

Marina H Wallace 1
  1. Fiona Stanley Hospital and UWA, Murdoch, WA, Australia

Familial Adenomatous Polyposis (FAP) is an autosomal dominant inherited disorder of the APC gene. It results in hundreds or thousands of adenomatous polyps in the colon which left untreated inevitably develop into colorectal cancer. Patients also have extra colonic manifestations of FAP which include: desmoid disease, non metastasising myofibroblastic tumours that can occur intra or extra abdominally; duodenal polyposis; gastric fundic gland polyps; dermoid cysts, benign bone cysts; and congenital hypertrophy of retinal pigment epithelium (CHRPE) 

Treatment depends on whether the patient is from a known FAP family, or has a new diagnosis as a result of symptomatic presentation. The talk will concentrate on how to manage both these groups.

If there is a known mutation in the family, children of patients with FAP can undergo genetic testing in their early teens. Those found to have the mutation are offered prophylactic colectomy at an appropriate time with respect to their schooling. If a mutation has not been detected in the family, children should undergo yearly flexible sigmoidoscopy screening from the age of 12 to 19. Beyond this if no polyps have been found they should have five yearly colonoscopies by an experienced endoscopist. 

As patients with FAP age, they are at risk of developing duodenal polyposis, which in a small percentage of patients can develop into malignancy. They need surveillance of the duodenum with side viewing endoscopy. The frequency of surveillance is tailored to the number of duodenal polyps found and is calculated using Spigelman's Stage Calculator. Patients are also at risk of developing desmoid disease, which if intrabdominal can lead to small bowel, vascular or ureteric obstruction.  

The management of patients and families with FAP should ideally be coordinated by Polyposis or Family Cancer Registries. These patients have complex emotional and physical needs which are not always appropriately managed by conventional pathways.

Patients who are not known to come from an established FAP family can present in a variety of ways. Commonly they present with malignancy and are found to have multiple polyps at time of preoperative investigation, or even at surgery. These patients should have the appropriate cancer management, but consideration should be made for them to be referred to a cancer geneticist and family members should be offered colonoscopic screening early. 

Asymptomatic patients can be diagnosed by optometrists or ophthalmologists during routine eye examinations where CHRPEs are discovered during fundal examination. These patients should be referred for colonoscopy by an experienced colonoscopist.

Although rare, FAP is an important inherited colorectal cancer condition, and these patients need careful coordinated care by clinicians experienced in their management.