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CANCER MANAGEMENT

CANCER CONTROL 2014 69

occurred within 3 months from the bleeding episode.9 Given

the fact that rectal bleeding affects 8-20% of the population

the characteristics of the bleeding requires attention:

painless bleeding or dark blood mixed with faeces are

significantly associated with CRC diagnosis.9,10 Changes in

bowel habits towards increased looseness or increased stool

frequency is more predictive than constipation.8 Research

evidence indicates that a combination of rectal bleeding, with

change in bowel habits, or one of these symptoms in persons

aged 60 and above should prompt urgent referral.8,10 A recent

review indicated rectal bleeding and weight loss as symptoms

with high positive predictive value for CRC diagnosis.11 Other

concomitant symptoms and signs with rectal bleeding

doubles the likelihood of a CRC diagnosis and, in contrast,

other symptoms in isolation have very low predictive value

for CRC.12

Symptoms of CRC differ depending on the location of the

tumour, from proximal to distal bowel. Those presenting with

proximal cancers may present without changes in bowel

habits, as the highly liquid stool may pass easily around even

large masses. Patients with cancers of the sigmoid and

rectum may pass bright red blood in stools which might be

mistaken by the patient as bleeding from haemorrhoids.

Difficulty on defecation or constipation can result from the

mass effect of tumours in the distal colon where the

stool is more bulky and unable to pass.

Early detection tests for CRC

Early detection tests for CRC include the chemical

faecal occult blood test (cFOBT), the immunochemical

FOBT (iFOBT), a digital rectal examination (DRE), a

double contrast barium enema, sigmoidoscopy,

endoscopic colonoscopy and virtual colonoscopy.

FOBT and DRE are feasible in PC, whereas the other

procedures can only be done in specialized services at

secondary or tertiary care centres by highly trained

specialists.

In a DRE, the anal canal and rectum are examined

with a lubricated, gloved finger. Although a DRE is

often included as part of a routine physical

examination, when patients complain of rectal bleeding or

other abdominal symptoms, it is not recommended as a

stand-alone test for CRC. This simple test, which is not

usually painful, can detect masses in the anal canal or lower

rectum. By itself, however, it is not a good test for detecting

CRC because its reach is limited and negative DRE does not

exclude CRC. A small amount of stool in the rectum when

doing a DRE is used by some general practitioners for cFOBT

or iFOBT. However, simply checking the stool obtained in this

fashion for bleeding with an FOBT is not an acceptable

method of early detection of CRC as the stool collected has

not recently transited through the colon and, therefore, is not

a representative sample of faeces. Research has shown that

this type of FOBT will miss more than 90% of CRC and polyps.

All patients with bright red blood in the stool should undergo

a DRE to assess if haemorrhoids are present. Any blood in the

stool in the absence of haemorrhoids should prompt an

immediate referral for colonoscopy.

Early detection tests such as FOBT could help general

practitioners in the early diagnosis of CRC. Such tests,

especially the iFOBT, should be accessible for PC

practitioners. The iFOBT is an early detection test that

detects occult (hidden) blood in the faeces. This test reacts

with globin, which is part of the human haemoglobin protein

Table 2: Frequency of colorectal cancer (CRC) among people with rectal bleeding in a cohort study in the United Kingdom

Age group Number of people with a People with CRC, diagnosed within Positive predictive

first episode of rectal bleeding 3 years from rectal bleeding value (%) for CRC diagnosis

15-44 years 5,489 8 0.15%

45-64 years 5,314 109 2.1%

65+ 4,494 221 4.9%

Total 15,289 338 2.2%

Adapted from reference

9

Table 1: Symptoms of colorectal cancer

‰ Blood in stools, from bright red (more distal tumours) to dark and

tarry (more proximal cancers) or dark stools.

‰ A persistent change in bowel habits, such as diarrhoea, increased

frequency of stools, constipation or narrowing of the stool that lasts

for more than 10 days.

‰ A feeling that one needs to have a bowel movement that is not

relieved by doing so.

‰ Feeling of incomplete evacuation after defecation.

‰ Inability to pass stools for a prolonged period of time (e.g. 1 week).

‰ Abdominal pain, cramps or bloating.

‰ Vomiting, especially after prolonged constipation.

‰ General weakness and fatigue.

‰ Unintended weight loss and/or loss of appetite.

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