Video 2 - classification of risk in the general population with no symptoms.
This is the second in a series of four short videos designed to provide information to GPs regarding bowel cancer screening in Australia. So this video covers the importance of age, and family history and that's in relation to the national bowel cancer screening guidelines.
The two major factors underpinning advice regarding asymptomatic screening in the NHMRC guidelines are age, and family history. So assessment of family history of cancer is vital.
As a general rule all patients coming through your practice need assessment of their family history, but in relation to bowel cancer this is particularly important. And what you really need to know are:
- How many family members have been affected by either bowel cancer or polyps?
- At what age were they affected?
- How are they related to your patient, i.e. are they first or second degree relatives?
You also need to ask about cancers that may be closely related through autosomal dominant syndromes such as HNPCC or Lynch syndrome, now these cancers include uterine cancer, ovarian cancer, or cancers of the urinary system.
The NHMRC guidelines define 3 levels of risk for asymptomatic patients:
Category 1 of those patients with no family history or a single affected relative over the age of 55. This is the target group of the national bowel cancer screening program, and these patients should be advised to commence biennial screening via FOBT from the age of 50.
Category 2 are those patients with a first degree relative affected under the age of 55 or two first degree relatives or a first and a second degree relative affected at any age. These patients require either regular colonoscopy or specialist advice. FOB testing through the National Bowel Cancer Screening Program is NOT appropriate for these patients.
Category 3 patients are those in whom the family history seems to suggest a pattern of autosomal dominant inheritance, i.e. multiple affected relatives linked by generations, especially if affected before the age of 50. These patients require not just specialist referral and advice, but referral to a Family Cancer Clinic for advice regarding genetic assessment.
Whilst these categories and their implications may be self-explanatory, there are of course a number of exceptions and considerations that need to be highlighted in terms of providing advice to patients:
Firstly, some patients may already be participating in a colonoscopy program. If there appears to be no guideline-based indication for participating in a colonoscopy program, i.e. no significant family history or personal history of colorectal neoplasia, or other risk factors, then it's important to discuss the categories with that patient, so that they are fully informed of their options and aware that they can participate in FOB testing only.
However, there will of course be patients in this category who have watched a close relative, over the age of 55, suffer from bowel cancer and its predictable sequelae. A significant number of these patients will, regardless of the guidelines, have formed their own opinion about their desire for colonoscopic screening, and it is of course difficult to advise against such a course of action if the patient has been adequately informed, including discussion of the risk of colonoscopic perforation, estimated to be 1 in approximately 1500 diagnostic scopes.
Secondly, the guidelines indicate that patients in Category 2, i.e. that is those with young affected relatives or multiple relatives, should be offered colonoscopy.
Thirdly, regardless of family history, some patients will previously have had adenomatous polyps, and therefore be participating within a colonoscopic surveillance program. There is really no point in encouraging patients to participate in faecal occult blood testing if they are already undergoing regular surveillance for an appropriate indication relating to previous adenomatous polyps. These patients should be encouraged to continue participating in a screening program as they are at increased risk.
Fourthly, consideration needs to be given to encouraging patients to undertake primary prevention. There are now well accepted guidelines including:
- encouraging patients to normalise their body mass index
- limit alcohol intake
- quit smoking
- and minimise their intake of processed foods, particularly foods that are charred or have been smoked.
Finally, there will of course be a cohort of patients who simply refuse to engage with the screening process and the National Program. It's imperative that these patients should be targeted by GPs for further education and encouragement; research has shown that GP endorsement of FOBT based screening for bowel cancer can positively influence participation rates.
Often within this patient cohort, there can be a distinct lack of knowledge about the importance of primary screening, and patients will often shelter behind the notion that, if they have no symptoms or perceive themselves as being 'fit and healthy', then they are immune from bowel cancer, which of course is not the case.
It is important to emphasise to these patients both the significant incidence of bowel cancer within Australian society and the demonstrated Level 1 evidence of an approximately one third reduction in the risk of mortality associated with bowel cancer for patients who participate in a screening program.
There is growing evidence of the incidence of colorectal cancer in the under 50 age group is increasing, although this is not the focus of these videos. And even though population-based screening is not currently recommended for people aged under 50, it's still important to assess bowel cancer risk with your younger patients looking for symptoms, and or, category 2 family history.
Don't forget, more than 1500 patients under 50 will be diagnosed with bowel cancer every year.
The next presentation will provide general information regarding the National Bowel Cancer Screening Program, followed by a series of case studies.