Signs and symptoms predictive of colorectal cancer
Systematic review evidence[edit source]
In symptomatic patients without a colorectal cancer diagnosis, what signs or symptoms (persistent changed bowel movements, persistent diarrhoea or constipation, unexplained rectal bleeding, general or localised abdominal pain, unexplained palpable abdominal or rectal mass, unexplained weight loss, iron deficient anaemia, tiredness, fatigue, or any combination) correlate best with a diagnosis of colorectal cancer? (SPT1-2a)
A systematic review of the predictive value of signs and symptoms of colorectal cancer was recently undertaken to inform the UK National Institute for Health and Care Excellence (NICE) guidelines. We updated the NICE systematic review to 31 August 2016, identifying two new relevant papers. The systematic reviews and meta-analyses focused on the positive predictive values of individual symptoms, signs and combinations of symptoms and, where possible, stratified these by age and sex. Some studies also included levels of haemoglobin and markers of iron deficiency from a full blood count.
Due to the nature of the research question, the studies included used mainly case-control and cohort designs and are therefore subject to several biases, including patient selection, non-consecutive patient sampling and missing data, especially in relation to specification of symptoms. All studies were conducted on Western populations, with the majority based on European populations, particularly in the UK. Only one study was conducted in Australia. However, the evidence is likely to be generalisable to the Australian average risk population presenting in primary care.
The NICE guidelines aimed to identify symptoms associated with a positive predictive value of at least 3% to inform selection for urgent referral for investigation of colorectal cancer. This threshold should be compared against the current positive predictive value of 3.5% for a positive immunochemical faecal occult blood test (iFOBT) in the Australian National Bowel Cancer Screening Program. For those patients with symptoms associated with a positive predictive value of below 3%, NICE developed a health economic model to test different diagnostic strategies in primary care. Specifically, they modelled the following tests in people aged 40 years and over with a change in bowel habit:
- faecal occult blood test using guaiac test
- faecal occult blood test using the immunochemical faecal occult blood test (iFOBT)
- barium enema
- flexible sigmoidoscopy
- CT colonography.
At a threshold of GBP20,000 (approximately $40,000) per quality-adjusted life year (QALY), iFOBT was the most cost-effective test in people aged 40 years and over with a change in bowel habit.
For details about this systematic review, please see the Technical report.
Evidence summary and recommendations[edit source]
|Rectal bleeding presenting in primary care was associated with a PPV for colorectal cancer of up to 4.8% (95% CI 3.3 to 6.8). This PPV tended to increase with age in both men and women.||II, III-2, III-3||, , , , , , , , , , , , , , |
|Abdominal pain presenting in primary care was associated with a PPV for colorectal cancer of up to 2.0% (95% CI 0.5 to 7.6). This PPV tended to increase with age in both men and women.||III-2, III-3||, , , |
|Anaemia* presenting in primary care was associated with a PPV for colorectal cancer of up to 5.8% (95% CI 2.6 to 12.0). This PPV tended to increase with age in both men and women.
Two new studies since the meta-analysis estimated the PPV for anaemia in referred populations as 10.2% (95% CI 4.6 to 17.3) and 12.0% (95% CI 8.0 to 16.0).
|II, III-2, III-3, IV||, , , , , , |
|Weight loss presenting in primary care was associated with a PPV for colorectal cancer of up to 3% (95% CI 0.3 to 22.9). This PPV tended to increase with age in both men and women.
One new study since the meta-analysis estimated the PPV for weight loss in a referred population as 5.2% (95% CI 2.5 to 9.2).
|II, III-2, III-3||, , |
|Dyspepsia presenting in primary care was associated with a PPV for colorectal cancer of up to 0.6% (95% CI 0.3 to 1.4).||III-2||, , |
* The available data did not allow clear distinction between iron-deficiency and non-iron deficiency anaemia. PPV: positive predictive value; CI: confidence interval
Individual studies[edit source]
|Constipation presenting in primary care in two studies was associated with a PPV for colorectal cancer of 0.4–2.5%. In one further small study in selected patients the estimated PPV was 15.7% (95% CI 10.2 to 23.2).||II, III-2, III-3||, , |
|Change in bowel habit presenting in primary care in two studies was associated with a PPV for colorectal cancer of 2.8–2.9%. This PPV tended to increase with age in both men and women. In one further small study in selected patients the estimated PPV was 14% (95% CI 6.7 to 23.3).||III-2||, , |
PPV: positive predictive value; CI: confidence interval
Combination of symptoms[edit source]
|Nine studies that examined the PPVs for rectal bleeding in combination with other symptoms reported wide-ranging estimates. Some studies reported other combinations of symptoms.
Combinations associated with higher estimated PPVs included:
Several of the estimates from these studies are likely to be artificially inflated due to small numbers of participants with specific combinations of symptoms.
|III-2, III-3, IV||, , , , , , , , |
PPV: positive predictive value; CI: confidence interval
Combinations of symptoms and baseline risk factors predicting prevalent cancer[edit source]
The QCancer colorectal cancer risk prediction model incorporates the following variables for men and women to calculate positive predictive values for combinations of multiple symptoms and baseline risk factors:
- Women: age, family history of gastrointestinal cancer, abdominal pain, appetite loss, rectal bleeding, weight loss, anaemia (< 11 g/dL).
- Men: age, family history of gastrointestinal cancer, alcohol consumption, abdominal pain, appetite loss, rectal bleeding, weight loss, anaemia (< 11 g/dL), change in bowel habit.
On internal validation the QCancer model showed good discrimination; the area under receiver operating curve (ROC) statistics were 0.89 for women and 0.91 for men. In an independent external validation study the ROC statistics were 0.92 for women and 0.91, and the risk prediction model explained 68% and 66% of the variation in women and men, respectively.
Consensus-based colonoscopy triage categories[edit source]
Table 10.1 presents triage categories to determine urgency and need for colonoscopy based on symptom profile, patient age and results from investigations available in primary care.
The guideline development group applied evidence about the predictive value of individual and combinations of symptoms, including allowance for patient age, to inform the development of colonoscopy triage categories. They build on Victorian draft guidelines for colonoscopy triage. The guideline development group discussed the use of additional investigations in primary care to support triage which had been informed by the NICE guidelines and had undergone extensive expert consultation.
In addition to its traditional use as a screening test in asymptomatic patients, iFOBT is potentially useful for assessing risk in symptomatic patients, especially those who have not recently participated in the NBCSP. In addition to the NICEmodelling study (see Systematic review evidence), we considered new evidence about the use of iFOBT and calprotectin in patients with bowel symptoms referred from primary care. This demonstrated that a negative iFOBT can be useful in ruling out significant bowel disease, including colorectal cancer. The study also showed that faecal calprotectin is a useful test in distinguishing patients with inflammatory bowel disease (IBD) and irritable bowel syndrome, consistent with international guidance on using this test to rule out IBD.
The guideline development group also discussed the role of CT colonography as an alternative investigation. CT colonography has high sensitivity for colorectal cancer and could potentially be used therefore to rule out this diagnosis in patients with bowel symptoms. CT colonography may be considered as an alternative diagnostic test, particularly in the following scenarios:
- Individuals with symptoms of colorectal cancer below the 3% CRC risk threshold.
- Individuals in areas with limited access to colonoscopy services but where there is access to CT.
- Individuals who have contra-indications to colonoscopy.
The New Zealand Society of Gastroenterology recommends CT colonography as an alternative to colonoscopy in: symptomatic patients over 80 years, individuals with an abdominal mass, and in those at higher risk of complications from colonoscopy. It should be noted that in the NICE modelling study of alternative testing strategies in individuals with symptoms of colorectal cancer below the 3% risk threshold, iFOBT was the most cost-effective investigation to support triage of referrals for colonoscopy. This modelling was set in a UK healthcare context and did not consider issues of differential access to colonoscopy and CT colonography.
Under current Medicare eligibility rules, GPs can only request CT colonography if a patient has had an incomplete colonoscopy in the previous 3 months or there is a contraindication to colonoscopy. This creates a significant barrier to its use in Australian primary care as an alternative test to colonoscopy in symptomatic individuals. It can be requested by a specialist ‘for exclusion of colorectal neoplasia in a symptomatic or high risk patient’, and therefore may have a potential role in triage for a colonoscopy triage setting.
Table 10.1. Colonoscopy triage categories[edit source]
|Category 1||Category 2||Category 3||No colonoscopy indicated|
|Positive immunochemical faecal occult blood test (iFOBT) (asymptomatic)|
|Anaemia and any one of:
||Anaemia and all of:
||Anaemia and all of:
||Anaemia and all of:
|Rectal bleeding < 12 months and any one of:
||Rectal bleeding < 12 months and all of:
||Rectal bleeding ≥ 12 months and all of:
||Rectal bleeding ≥ 12 months and all of:
|Altered bowel habit > 6/52 and any one of:
||Altered bowel habit > 6/52 and all of:
||Altered bowel habit > 6/52 and either:
|Unexplained abdominal pain and any one of:
||Unexplained abdominal pain and all of:
||Unexplained abdominal pain and either:
|A resolved episode of acute abdominal pain**
or Diverticulitis with typical CT features and no other GI symptoms
|Unexplained weight loss and any one of:
||Unexplained weight loss and all of:
||Unexplained weight loss and all of:
|Mass palpable on abdominal or rectal examination or on rigid sigmoidoscopy|
Source: Victorian Colonoscopy Categorisation Guidelines
GI: gastrointestinal; > 6/52: symptom present for more than 6 weeks per episode; CT: computed tomography NB. Faecal calprotectin is a useful test in distinguishing patients with inflammatory bowel disease and irritable bowel syndrome, but has no role in detecting colorectal cancer. There is currently no Medicare Benefits Scheme (MBS) rebate for calprotectin.
**Abdominal pain present for less than 5 weeks should be assessed and treated, with consideration of colonoscopy if no response.
In people with symptoms other than overt rectal bleeding, immunochemical faecal occult blood testing (iFOBT) can be used as part of the diagnostic assessment in primary care.
Benefits and harms[edit source]
The recommendations aim to support a rational process to determine the urgency of colonoscopies, particularly in the context of long waiting lists for colonoscopy in the public hospital system. It should be noted that no symptoms are strongly predictive of colorectal cancer, nor are there any symptoms which rule out cancer. Thus it remains possible that even patients in Category 3, who have ‘low risk but not no risk’ symptoms, may eventually be diagnosed with colorectal cancer. Those patients who do not meet criteria for colonoscopy should be reviewed by their GP and reconsider the need for investigation if new symptoms or signs have developed.
Health system implications[edit source]
Clinical practice[edit source]
The triage categories, while moderately complex, are designed for use by endoscopy units to assess the urgency of referrals for colonoscopy. GPs should apply this evidence to inform their use of simple investigations in primary care (full blood count, iron studies and iFOBT) as part of their assessment of patients with symptoms suggestive of colorectal cancer. It should also be noted which patients are identified in this guideline as not requiring referral for colonoscopy.
Health services and endoscopy units should consider implementing specific GP referral proformas designed to capture the information needed to apply the triage criteria.
Endoscopy units may need dedicated staff to apply the triage criteria consistently.
Barriers to implementation[edit source]
Unresolved issues[edit source]
Timely diagnosis of colorectal cancer is important for improving survival. The triage criteria are designed to improve the efficiency of the referral and triage processes for people with symptoms suggestive of colorectal cancer, but further evidence is required on the impacts of their implementation.
Studies currently underway[edit source]
The Victorian colonoscopy guidelines are currently being piloted to assess their feasibility of implementation.
Future research priorities[edit source]
Further research is needed to determine how best to reduce missed opportunities for colorectal cancer diagnosis in primary care, applying the evidence about symptoms as predictors of colorectal cancer risk.
The colonoscopy triage criteria are based on current best evidence. The following further research is needed to evaluate their implementation:
- prospective, comparative validation studies measuring clinical outcomes
- studies assessing the impact on waiting times, diagnostic intervals and colorectal cancer outcomes.
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