‘Inconsistent investigation’ of colorectal cancer symptoms

An Australian study has found ‘substantial variation’ in the way colorectal cancer-related symptoms are investigated and managed in general practice. 
 
And although some of that variation reflects ‘appropriate clinical judgement’, 
researchers say ‘inconsistent investigation, especially for non-specific symptoms, indicates potential missed diagnostic opportunities’. 
 
Published in the British Journal of General Practice, the retrospective study used data from 70,107 patients aged 40 and over presenting with symptoms between 2008–22. 
 
The proportion of patients receiving diagnostic actions was assessed, including medications, pathology, imaging, colonoscopy, or specialist referral. 
 
Abdominal pain (32%) and diarrhoea (21%) were the most frequent presentations to primary care. 
 
No investigation or treatment occurred in 50% of cases for those presenting with constipation and diarrhoea and in 20% of cases where there had been a change in bowel habits.  
 
Medication-only management, or ‘tests of treatment’, occurred more for diarrhoea and constipation,  whereas blood and imaging tests were common for abdominal pain and abdominal mass.  
 
Colonoscopy or specialist referral was highest for rectal bleeding (67%) and change in bowel habit (60%). 
 
Results also showed that within the study population, 378 patients (0.5%) were diagnosed with colorectal cancer within 12 months – anaemia had the highest positive predictive value (PPV) followed by rectal bleeding. 
 
Researchers say ‘the low anaemia investigation rate is concerning and warrants further study but raises broader concerns about managing abnormal test results in primary care.’ 
 
‘The overall colorectal cancer diagnosis rate was only 0.5%, with even “red flag” symptoms such as anaemia and rectal bleeding having PPV <2%, reflecting the diagnostic challenge faced by GPs in selecting patients for diagnostic colonoscopy,’ they wrote. 
 
Associate Professor Joel Rhee, RACGP Specific Interests Cancer and Palliative Care Chair, said this is a large and useful study, however it does not capture all the clinical context relevant to a GP consultation.  
 
‘For example, we don’t really know how long symptoms had been present, how severe they were, whether they were changing, or whether there was already a likely explanation,’ he told newsGP. 
 
‘As an example, three days of diarrhoea are very different from three months. The former is not a colorectal cancer symptom, while the latter is (and is less likely to be common), and that context matters clinically.  
 
‘We also don’t know whether patients had already had relevant investigations, diagnoses or are already under non-GP specialist care. For example, a known, episodic and self-limiting episode of a red flag symptom such as rectal bleeding may not require investigation if it is unchanged, the patient has already been appropriately investigated, and there is a known benign cause such as haemorrhoids. 
 
‘Because of these limitations, the study does not allow us to conclude whether GPs are generally under-investigating, over-investigating, or doing the right amount of investigation overall. We simply don’t know how many of the symptoms are concerning for colorectal cancer.’ 
 
Associate Professor Rhee said there are reassuring findings in the study, as well as some that signal concern. 
 
‘Red flag symptoms such as rectal bleeding were more likely to be investigated with colonoscopy. This is appropriate and reassuring,’ he said. 
 
‘The finding that people with multiple symptoms or repeat presentations were more likely to be investigated also fits with how GPs think clinically.’ 
 
Concerningly, however, was the finding that patients from disadvantaged areas received fewer investigations overall, ‘with more primary care tests than specialist referrals’. 
 
‘The socioeconomic gradient is highly concerning, and the rural gradient is also concerning, although the study suggests practice-level variation plays a significant role. This clearly needs further research,’ Associate Professor Rhee said. 
 
Patients aged over 80 and under 50 were also less likely to be investigated than those aged 50–79 years.  
 
According to Bowel Cancer Australia, the risk of being diagnosed before age 40 has more than doubled since 2000, and one in nine new bowel cancer cases now occur in people aged under 50. 
 
To increase early diagnosis, the authors suggested GPs need systematic, evidence-based approaches to investigate lower gastrointestinal symptoms that balance cancer detection with avoiding over-investigation. 
 
‘This includes developing structured diagnostic pathways, improving integration of decision support tools, and establishing mechanisms to enhance follow-up of abnormal results,’ they said.  
 
‘Further research is necessary to explore the effects of current investigation practices on diagnostic intervals, stage at diagnosis, and cancer outcomes.’ 
 
But Associate Professor Rhee notes ‘this is not just a GP issue’.  
 
‘Non-GP specialists and health services should examine these findings and consider what system-level changes are needed,’ he said.  
 
‘One urgent issue is the need for better access to publicly funded endoscopy services, particularly in rural and regional areas.  
 
‘It’s also important to remember that most bowel symptoms in general practice do not turn out to be cancer, even when they are symptoms we take seriously.  
 
‘The challenge is not simply “do more colonoscopies”, but making sure patients with concerning or persistent symptoms can access timely investigation.’ 

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