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What you need to know about bowel cancer

Colorectal surgeon Mr Ian Daniels answers GP Dr Sabby Kant's questions on red flag symptoms, the usefulness of faecal occult blood tests and differentiating IBS from cancer.

Colorectal surgeon Mr Ian Daniels answers GP Dr Sabby Kant's questions on red flag symptoms, the usefulness of faecal occult blood tests and differentiating IBS from cancer.

1 Can you summarise the environmental factors in the development of bowel cancer?

41237153There are around 36,000 cases of colorectal cancer in the UK each year, with around 15,000 deaths from the disease. About two-thirds of cancers are colonic and one-third rectal. The male-to-female ratio is 3:2 and this gender bias is most pronounced in rectal cancer.

Multiple dietary and environmental factors influence the aetiology and, although the highest incidence is in Caucasians, the incidence in other ethnic groups is rising.

EPIC – the largest study of diet and disease with more than half a million European participants – concluded that diets low in fibre and vegetables but rich in processed and red meats and animal fats predisposed to bowel cancer1.

2 And what about the genetic factors?

Most bowel cancers are sporadic, with the incidence increasing with age. Colorectal cancer is rare in the under 40s but increases from age 45 (25 cases per 100,000) to the over-75s (300 per 100,000).

But there is also a genetic component. Many of us are aware of familial polyposis coli – although this causes fewer than 1% of colorectal cancers. In this condition the development of polyps through the teens and twenties leads to colorectal cancer in almost all by age 40 but these patients are usually part of recognised families and screened early.

Those affected are offered prophylactic proctocolectomy and reconstruction with an ileoanal pouch.

About 8% of colorectal cancers are the hereditary non-polyposis type, characterised by DNA-mismatch repair gene abnormalities. The Amsterdam criteria are used to identify these families for screening, that is: three family members affected, in two generations, and one case must be aged under 50 at diagnosis2.

Patients with colitis – either ulcerative colitis or Crohn's disease – also need close surveillance and should be part of a local follow-up policy with regular colonoscopic surveillance.

Referral to a geneticist is usually made after a careful family history is taken, including non-GI cancers (breast, ovarian and endometrial).

If the individual is the first-degree relative of a patient with bowel cancer – or is from a family that meets the Amsterdam criteria – then referral to a geneticist should be considered2. There is no strict policy, nor guidelines, for patients who do not fit the criteria.

My own practice is to discuss the family history and the options for assessing the bowel – faecal occult blood test (FOBT) or colonoscopy – as well as discussing the risks and benefits of each and to let the patient make an informed choice.

3 How can GPs decide whether they should be excluding bowel cancer in patients with IBS-type symptoms?

The classical symptoms of IBS – bloating, erratic bowel habit, constipation and diarrhoea – can all be seen in undiagnosed malignancy.

As mentioned above, the incidence of bowel cancer is low in the under-40s. Older patients with a new presentation of symptoms should probably have a trial of therapy or given advice for their symptoms, but if they do not resolve should be investigated to exclude another condition.

The difficulty is that many IBS symptoms overlap with those of malignancy and many patients have been diagnosed with IBS over the years and therefore often relate any new symptoms to it.

But bleeding is not associated with IBS and should be considered significant.

4 What's the rationale for the national bowel cancer screening programme and is it proving useful?

The accepted theory for bowel cancer development is the adenoma carcinoma sequence – a step-wise progression through the development of a small adenomatous polyp that develops in the bowel mucosa.

This may increase in size and then changes from mild to severe dysplasia before invading the basement membrane of the bowel wall and becoming a cancer.

This process may take seven to 10 years, so there is a lead-time during which a polyp forms before becoming a cancer. Similarly, once the cancer has developed there is a further lead time before symptoms arise.

The current screening programme was developed to try to identify patients earlier in this process through the use of FOBT. Both polyps and cancer have unstable mucosa and are likely to bleed because of neo-angiogenesis.

There have been a number of screening pilot studies and projects over the past 20 years3. All people aged 60-69 are invited to take part and this is to be extended to those aged 50-69. But we will only be able to assess the benefits if we see a reduction in bowel cancers through high-risk polyp excision and earlier cancer diagnoses.

There are a number of other research initiatives currently assessing other ways of screening patients, but at present it's important to advise patients to accept the invitation for screening.

5 What's the role of FOBT in primary care, outside of the screening programme?

For patients concerned about symptoms, FOBT is a useful procedure with relatively low risk. Three samples need to be assessed and two positives out of three should prompt a referral. A single or weak positive could be repeated after a short time.

But if symptoms persist, despite negative FOBT, then referral may still be considered.

There is an increasing use of carcino-embryonic antigen testing (CEA) in primary care. But CEA may be raised in a number of conditions and can be up to twice the normal limit in smokers and hypoxic patients. So it is best used for monitoring disease recurrence and has no role in screening or diagnosing colorectal cancer.

6 What lifestyle measures can I confidently recommend to patients anxious to reduce their risk of bowel cancer?

Although a reduction in weight, increased fibre and vegetable intake, reduced red meat consumption and smoking cessation may reduce the risk for bowel cancer, many of these patients are already at an age where the incidence of the disease is increasing.

It may be better to encourage the earlier recognition of symptoms and tell patients not to be embarrassed about discussing a change of bowel habit or anal symptoms. Similarly encouraging patients to look at their faeces can lead to earlier recognition of change or the presence of blood.

There are a number of current research projects looking into ways to reduce polyp formation and these include work on short- and long-chain fatty acids, salicylates, probiotics and faecal DNA analysis4.

7 What are the key red-flag clinical features for bowel cancer? How frequently, and in what combinations, do they present in general practice?

The key red-flag symptoms are:

• rectal bleeding without anal symptoms in patients over 60

• change of bowel habit to looser and/or increased frequency of stools without rectal bleeding for more than six weeks in patients over 60

• rectal bleeding with persistent change of bowel habit to looser stools and/or increased frequency of defaecation

• a definite right-sided abdominal mass

• a definite palpable rectal mass

• iron-deficiency anaemia without an obvious cause.

The difficulty with these criteria is the patients' assessment of time, the heterogeneity of the symptoms and the fact that patients with a bowel cancer may also have constipation, tenesmus, abdominal pain, bloating and weight loss.

In our hospital, the cancer detection rate is 9% for patients referred through the two-week rule. Other patients will present with colitis, polyps and so on, although the symptoms are neither very specific nor sensitive.

8 Could you summarise the main investigations required for suspected bowel cancer?

Colonoscopy is the current ‘gold standard' for assessing a patient's large bowel. But it is an invasive procedure and the bowel preparation is not risk-free.

Some patients are not well enough for colonoscopy so CT scanning may be used to exclude a gross malignancy and virtual colonoscopy has an increasing role, but still requires bowel preparation.

Other diagnostic tests are currently in development, based upon faecal tagging, colonocyte capture and stool DNA profiling.

Barium enemas are still used and can be useful when diverticulosis is suspected.

In those patients diagnosed with colon cancer, a CT scan of thorax/abdomen and pelvis is arranged prior to review at the multidisciplinary team (MDT) meeting.

Any other investigations, such as PET scans, are arranged and for suspected rectal cancer, an MRI scan is also performed to assess the relationship of the tumour invasion (T-stage) to surgical resection margin.

Radiological staging of the disease will lead treatment selection. In fact, MRI staging of rectal cancer has dramatically cut recurrence rates.

9 What's the GP's role in monitoring patients after treatment?

Following treatment for bowel cancer, patients should be discussed at the post-operative MDT meeting. Depending upon local policy, a plan will be made depending on their histopathology, but also on other factors such as comorbidity, age and so on.

For some patients, annual CT scanning may be enough and some may even be discharged from further investigation. But rather than arrange routine outpatient follow-up, local policies for bowel cancer follow-up could be initiated between primary and secondary care.

10 What are the main treatments?

Surgery is the principal treatment in bowel cancer. For colonic cancer, primary surgery for curative intent (no evidence of metastases on pre-operative imaging) or for symptom control (obstructed/bleeding tumours) is used.

After surgery, histopathological assessment of the specimen will allow staging of the tumour and then MDT discussion will lead to a postoperative plan. This may involve adjuvant chemotherapy (in the presence of nodal disease, extra-mural vascular invasion, poor differentiation or tumour perforation) and therefore referral to an oncologist. However, a new clinical trial, FOxTroT, is currently recruiting patients to assess the role of preoperative chemotherapy5.

In rectal cancer, MRI will inform the MDT's discussion. In patients with locally advanced disease, preoperative chemo-radiotherapy is offered to down-size/down-stage the tumour before surgery. This is usually five weeks of daily radiotherapy and concurrent chemotherapy. These patients are then restaged before a further MDT discussion and surgery.

MRI has had a huge impact on the outcome for patients with rectal cancer as it is used to select those for primary surgery. Similarly, the development of specialist rectal cancer surgeons with low rates of incomplete resections has had an impact.

11 What support is there for patients with colorectal cancer?

With the development of MDTs, there has been an increase in the number of specialist nurses that are involved in patient care. Each MDT has a number of colorectal nurse specialists who may counsel patients, discuss diagnosis and treatment, co-ordinate investigations and treatments as well as following up patients after treatment as part of the continuity of care. They can also be a useful link with primary care in planning treatment for patients when social care, comorbidities, and so, may influence these decisions.

Improved stoma care and the development of specialist stoma clinics has led to improved outcomes for those patients for whom appliance security and stoma management can increase dramatically quality of life.

For many patients access to the internet can lead to confusing information and recommended sites include Cancer BACUP, Cancer Research UK, Macmillan and DiPEX in the UK.

Mr Ian Daniels is consultant general and colorectal surgeon at the Royal Devon and Exeter NHS Foundation Trust

Competing interests: none declared

Precancerous polyp in colon Precancerous polyp in colon What I will do now What I will do now

Dr Sabby Kant considers the responses to his questions

We've all heard of patients wrongly labelled as having IBS and ending up with an often delayed diagnosis of colon cancer. So the author's emphasis of the significant overlap of symptoms in both these conditions is useful. More crucially he highlights that rectal bleeding is not associated with irritable bowel and should be considered significant.
Although our GP training has honed us into being aware of familial polyposis coli, these cases make up less than 1% of colon cancers, whereas 8% are the hereditary non-polyposis type.
Practical advice regarding faecal occult blood testing in primary care is welcome, too, as is the advice that tumour markers such as CEA are useful for disease monitoring but have no role in screening, partly because of their high false-positive rate.
The EPIC study adds robust evidence for the role of the GP in preventing bowel cancer by urging patients to increase their fibre and vegetable intake and reduce processed food and red meats.
The red-flag bullet list will help us decide which patients to fast-track. The usefulness and practical validity of referring suspected cases is confirmed by the fact that almost one in 10 of those referred via the two-week fast track end up with a cancer diagnosis.

Dr Sabby Kant is a GP in Hillingdon, Middlesex

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