The aim of the NZFGCS is to reduce the number of cancers occurring in families by facilitating the required bowel screening
New Zealand has a high incidence of bowel cancer, with approximately 6% of New Zealanders (1 in every 16) developing bowel cancer by the age of 75 years. Most bowel cancer (90%) is diagnosed in people over the age of 50 years and, in most individuals, it develops over a 5-10 year period from a particular type of bowel polyp called an adenoma. A polyp is an outgrowth from the bowel and there can be various types of polyps. The most common types are adenomas and serrated polyps.
Hyperplastic or serrated polyps have been recognised for many years. Often a few small (less than 5mm) hyperplastic polyps are seen in the distal bowel; the rectum or back-passage. These are considered to be of no concern. However, it is now recognised that some serrated polyps may progress to bowel cancer and this risk is increased if hyperplastic or serrated polyps are present throughout the whole large bowel (colon). Based on how they look under the microscope, serrated polyps can be sub-categorised to identify which may be more likely to progress to bowel cancer. These ‘advanced’ serrated polyps tend to occur in the proximal large bowel (right side of the colon) and may be quite flat and difficult to find during colonoscopy.
A diagnosis of SPS is made when an individual is identified to have over 20 serrated polyps throughout the colon or where there are at least five such polyps but two are large (10 mm or more in size). Sometimes during a colonoscopy for another reason, there may be a suspicion that a diagnosis of SPS is likely, but not quite enough polyps to be sure. For this reason, when making a diagnosis of SPS, all serrated polyps removed at any previous colonoscopy are counted together.
It has been recognised that approximately 30-50% of patients with SPS present with bowel cancer. Unfortunately, we do not actually know the true risk for developing bowel cancer. It is estimated that 1 in 3,000 people in the population have SPS, but we do not know how many of those people will go on to develop a bowel cancer in their lifetime. It is clear however that it is more likely than people in the general population.
SPS is not consistently associated with development of other types of cancer. There may be a slight increase in risk of pancreatic cancer in SPS patients or their first-degree relatives.
Smoking increases the number of both adenomatous and hyperplastic or serrated polyps but it appears to particularly increase the number of serrated polyps. We recommend avoiding smoking for this reason.
There are no known means by which we can reduce the development of the serrated polyps, but we do recommend a standard healthy diet, maintenance of ideal body weight and regular exercise. Health NZ has very helpful eating and activity guidelines available on their website.
A number of studies have now documented the importance of frequent colonoscopy with removal of polyps in individuals identified to have SPS. Taking off larger polyps is done carefully, so initially your specialist may perform quite frequent colonoscopies to safely remove all the larger polyps present. Colonoscopy is usually offered one to two-yearly once the number of polyps growing has been brought under control (in other words if there are not too many polyps developing in between inspections).
Serrated polyps can be very hard to detect during colonoscopy because, even when large, they are very flat and often have a mucous cap hiding them. It is therefore very important that your bowel is as clean as possible from the bowel preparation to give the endoscopist the best chance of finding them. Ensure you follow completely the preparation instructions provided before your colonoscopy and, if you notice that you are still passing brown or murky stool before you are due to arrive at the endoscopy unit, call ahead to see if an enema or more preparation can be offered to help clear your bowel completely.
If SPS patients develop new bowel symptoms, like bleeding from the back passage, or their bowel pattern becomes more frequent, or the stool becomes consistently looser, or unexplained abdominal pain develops, they should see their doctor promptly to discussed these changes.
In rare occasions, it is just not possible to safely remove all polyps present by colonoscopy, either because they are too large, or too numerous, or because they prove to have very advanced features when examined under the microscope. In this small percentage of patients with SPS, surgery to remove the bowel with all the polyps may be advised. This does not usually involve a stoma (colostomy/ileostomy).
For the majority of patients, we do not know why they develop SPS. A genetic predisposition to developing SPS is suspected because up to 50% of individuals with SPS may have a family history of bowel cancer. It is possible that SPS may be “weakly inherited” requiring a number of minor genetic predispositions, from both parents, to be inherited together. SPS is certainly much more common in individuals of European or Celtic descent.
Genetic spelling mistakes, or mutations, have been reported in the RNF43 gene in several SPS patients, although these reported RNF43 variants do not account for the majority of people with SPS. Serrated polyps can also be seen in patients with other polyposis syndromes. Multi-gene panel testing in people with confirmed SPS is unfortunately not helpful because it is so rare that a mutation is found that will help us manage you or your family.
We are involved in a research study seeking to identify the genes associated with this condition. If you were diagnosed with the SPS before age 70 years, especially if you have lots of polyps, you may be eligible to participate in the study. We invite eligible SPS patients to participate by sending them a specific information sheet.
First-degree relatives (FDRs) are those people most closely related to you with a shared gene profile; your mother, father, brothers, sisters or children.
Your FDRs are more likely to develop serrated polyps, or SPS themselves, when compared to the general population. Not all do however.
FDRs of SPS individuals also have a five-fold increase in their risk of developing bowel cancer over their lifetime. For this reason, it is recommended that FDRs be offered screening by colonoscopy every five years. Usually this starts when they turn 40 years, but should start when they are 10 years younger than the earliest age at which SPS was diagnosed in the family.
If your FDRs develop new bowel symptoms, they should discuss them with their doctor promptly. Specifically, symptoms to look out for include bleeding from the back passage, persistent diarrhoea or unexplained persistent abdominal pain.