Key clinical points

NICE cancer referral guidelines for colorectal cancer suggest the following:


Refer adults using a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer if:
  • they are aged 40 and over with unexplained weight loss and abdominal pain or
  • they are aged 50 and over with unexplained rectal bleeding or
  • they are aged 60 and over with:
    • iron‑deficiency anaemia or
    • changes in their bowel habit, or
  • tests show occult blood in their faeces.

Consider a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer in adults with a rectal or abdominal mass.

Consider a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer in adults aged under 50 with rectal bleeding and any of the following unexplained symptoms or findings:

Introduction

Colorectal cancer is the third most common type of cancer in the UK and the second most cause of cancer deaths. Annually there are about 150,000 new cases diagnosed and 50,000 deaths from the disease.

Epidemiology

  • Incidence: 64.00 cases per 100,000 person-years
  • Peak incidence: 70+ years
  • Sex ratio: more common in males 1.3:1
Condition Relative
incidence
Diverticulitis3.91
Colorectal cancer1
Crohn's disease0.17
Ulcerative colitis0.16
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Pathophysiology

Location

Location of cancer (averages)
  • rectal: 40%
  • sigmoid: 30%
  • descending colon: 5%
  • transverse colon: 10%
  • ascending colon and caecum: 15%

Genetics

It is currently thought there are three types of colon cancer:
  • sporadic (95%)
  • hereditary non-polyposis colorectal carcinoma (HNPCC, 5%)
  • familial adenomatous polyposis (FAP, <1%)

Studies have shown that sporadic colon cancer may be due to a series of genetic mutations. For example, more than half of colon cancers show allelic loss of the APC gene. It is believed a further series of gene abnormalities e.g. activation of the K-ras oncogene, deletion of p53 and DCC tumour suppressor genes lead to invasive carcinoma

HNPCC, an autosomal dominant condition, is the most common form of inherited colon cancer. Around 90% of patients develop cancers, often of the proximal colon, which are usually poorly differentiated and highly aggressive. Currently seven mutations have been identified, which affect genes involved in DNA mismatch repair leading to microsatellite instability. The most common genes involved are:
  • MSH2 (60% of cases)
  • MLH1 (30%)

Patients with HNPCC are also at a higher risk of other cancers, with endometrial cancer being the next most common association, after colon cancer.

The Amsterdam criteria are sometimes used to aid diagnosis:
  • at least 3 family members with colon cancer
  • the cases span at least two generations
  • at least one case diagnosed before the age of 50 years

FAP is a rare autosomal dominant condition which leads to the formation of hundreds of polyps by the age of 30-40 years. Patients inevitably develop carcinoma. It is due to a mutation in a tumour suppressor gene called adenomatous polyposis coli gene (APC), located on chromosome 5. Genetic testing can be done by analysing DNA from a patient's white blood cells. Patients generally have a total colectomy with ileo-anal pouch formation in their twenties.

Patients with FAP are also at risk from duodenal tumours. A variant of FAP called Gardner's syndrome can also feature osteomas of the skull and mandible, retinal pigmentation, thyroid carcinoma and epidermoid cysts on the skin

Clinical features

Symptoms
Signs
  • Abdominal swelling (13%): An abdominal mass is found in around 13% of patients on presentation, with a rectal mass being found in around 25% of patients with rectal cancer.
Investigations

Referral criteria

NICE cancer referral guidelines for colorectal cancer suggest the following:


Refer adults using a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer if:
  • they are aged 40 and over with unexplained weight loss and abdominal pain or
  • they are aged 50 and over with unexplained rectal bleeding or
  • they are aged 60 and over with:
    • iron‑deficiency anaemia or
    • changes in their bowel habit, or
  • tests show occult blood in their faeces.

Consider a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer in adults with a rectal or abdominal mass.

Consider a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer in adults aged under 50 with rectal bleeding and any of the following unexplained symptoms or findings:
  • abdominal pain
  • change in bowel habit
  • weight loss
  • iron‑deficiency anaemia.


Faecal Occult Blood Testing (FOBT)

This was one of the main changes in 2015. Remember that the NHS now has a national screening programme offering screening every 2 years to all men and women aged 60 to 74 years. Patients aged over 74 years may request screening.

In addition FOBT should be offered to:
  • patients >= 50 years with unexplained abdominal pain OR weight loss
  • patients < 60 years with changes in their bowel habit OR iron deficiency anaemia
  • patients >= 60 years who have anaemia even in the absence of iron deficiency

Management

All patients with newly diagnosed colorectal cancer should have the following for staging:

Their entire colon should have been evaluated with colonoscopy or CT colonography. Patients whose tumours lie below the peritoneal reflection should have their mesorectum evaluated with MRI.

Once their staging is complete patients should be discussed within a dedicated colorectal MDT meeting and a treatment plan formulated.


Treatment of colonic cancer

Cancer of the colon is nearly always treated with surgery. Stents, surgical bypass and diversion stomas may all be used as palliative adjuncts. Resectional surgery is the only option for cure in patients with colon cancer. The procedure is tailored to the patient and the tumour location. The lymphatic drainage of the colon follows the arterial supply and therefore most resections are tailored around the resection of particular lymphatic chains (e.g. ileo-colic pedicle for right sided tumours). Some patients may have confounding factors that will govern the choice of procedure, for example a tumour in a patient from a HNPCC family may be better served with a panproctocolectomy rather than segmental resection.

Following resection the decision has to be made regarding restoration of continuity. For an anastomosis to heal the key technical factors include; adequate blood supply, mucosal apposition and no tissue tension. Surrounding sepsis, unstable patients and inexperienced surgeons may compromise these key principles and in such circumstances it may be safer to construct an end stoma rather than attempting an anastomosis.

When a colonic cancer presents with an obstructing lesion; the options are to either stent it or resect. In modern practice it is unusual to simply defunction a colonic tumour with a proximal loop stoma. This differs from the situation in the rectum (see below).

Following resection patients with risk factors for disease recurrence are usually offered chemotherapy, a combination of 5FU and oxaliplatin is common.


Treatment of rectal cancer

The management of rectal cancer is slightly different to that of colonic cancer. This reflects the rectum's anatomical location and the challenges posed as a result. Tumours located in the rectum can be surgically resected with either an anterior resection or an abdomino-perineal excision of rectum (APER). The technical aspects governing the choice between these two procedures can be complex to appreciate and the main point to appreciate for the exam is that involvement of the sphincter complex or very low tumours require APER. In the rectum a 2cm distal clearance margin is required and this may also impact on the procedure chosen. In addition to excision of the rectal tube an integral part of the procedure is a meticulous dissection of the mesorectal fat and lymph nodes (total mesorectal excision/ TME).

In rectal cancer surgery involvement of the cirumferential resection margin carries a high risk of disease recurrence. Because the rectum is an extraperitoneal structure (until you remove it that is!) it is possible to irradiate it, something which cannot be offered for colonic tumours. This has a major impact in rectal cancer treatment and many patients will be offered neoadjuvent radiotherapy (both long and short course) prior to resectional surgery. Patients with T1 and 2 /N0 disease on imaging do not require irradiation and should proceed straight to surgery. Patients with T4 disease will typically have long course chemo radiotherapy. Those with T3 , N0 tumours may be offered short course radiotherapy prior to surgery. Patients presenting with large bowel obstruction from rectal cancer should not undergo resectional surgery without staging as primary treatment (very different from colonic cancer). This is because rectal surgery is more technically demanding, the anastomotic leak rate is higher and the danger of a positive resection margin in an unstaged patient is high. Therefore patients with obstructing rectal cancer should have a defunctioning loop colostomy.


Summary of procedures

The operations for cancer are segmental resections based on blood supply and lymphatic drainage.

Site of cancer Type of resection Anastomosis
Caecal, ascending or proximal transverse colon Right hemicolectomy Ileo-colic
Distal transverse, descending colon Left hemicolectomy Colo-colon
Sigmoid colon High anterior resection Colo-rectal
Upper rectum Anterior resection (TME) Colo-rectal
Low rectum Anterior resection (Low TME) Colo-rectal
(+/- Defunctioning stoma)
Anal verge Abdomino-perineal excision of rectum None

In the emergency setting where the bowel has perforated the risk of an anastomosis is much greater, particularly when the anastomosis is colon-colon. In this situation an end colostomy is often safer and can be reversed later. When resection of the sigmoid colon is performed and an end colostomy is fashioned the operation is referred to as a Hartmans procedure. Whilst left-sided resections are more risky, ileo-colic anastomoses are relatively safe even in the emergency setting and do not need to be defunctioned.

Screening and prevention

Overview
  • most cancers develop from adenomatous polyps. Screening for colorectal cancer has been shown to reduce mortality by 16%
  • the NHS offers home-based, Faecal Immunochemical Test (FIT) screening to older adults
  • another type of screening is also being rolled out - a one-off flexible sigmoidoscopy


Faecal Immunochemical Test (FIT) screening

Key points
  • the NHS now has a national screening programme offering screening every 2 years to all men and women aged 60 to 74 years in England, 50 to 74 years in Scotland. Patients aged over 74 years may request screening
  • eligible patients are sent Faecal Immunochemical Test (FIT) tests through the post
  • a type of faecal occult blood (FOB) test which uses antibodies that specifically recognise human haemoglobin (Hb)
  • used to detect, and can quantify, the amount of human blood in a single stool sample
  • advantages over conventional FOB tests is that it only detects human haemoglobin, as opposed to animal haemoglobin ingested through diet
  • only one faecal sample is needed compared to the 2-3 for conventional FOB tests
  • whilst a numerical value is generated, this is not reported to the patient or GP, who will instead be informed if the test is normal or abnormal
  • patients with abnormal results are offered a colonoscopy

At colonoscopy, approximately:
  • 5 out of 10 patients will have a normal exam
  • 4 out of 10 patients will be found to have polyps which may be removed due to their premalignant potential
  • 1 out of 10 patients will be found to have cancer


Flexible sigmoidoscopy screening

Key points
  • screening for bowel cancer using sigmoidoscopy is being rolled out as part of the NHS screening program
  • the aim (other than to detect asymptomatic cancers) is to allow the detection and treatment of polyps, reducing the future risk of colorectal cancer
  • this is being offered to people who are 55-years-old
  • NHS patient information leaflets refer to this as 'bowel scope screening'
  • patients can self-refer for bowel screening with sigmoidoscopy up to the age of 60, if the offer of routine one-off screening at age 55 had not been taken up