New Australian data reveals large gaps in testing, with age and socioeconomic status influencing care.
A significant proportion of patients presenting to general practice with symptoms linked to colorectal cancer receive no diagnostic investigation, according to researchers from the University of Melbourne and University of Sydney.
They performed a retrospective cohort study of 70,107 patients aged 40 years and older presenting with colorectal cancer-related symptoms between 2008 and 2022, with the findings raising concerns about missed opportunities for early detection.
Abdominal pain (32%) and diarrhoea (21%) were the most common presenting symptoms, and no investigation or treatment occurred in half of patients. Only 20% of those presenting with change in bowel habit received treatment or investigation.
Instead, a “test of treatment” approach was frequently used. Medication-only management was most common for diarrhoea (11%) and constipation (23%), with opioid antidiarrhoeals prescribed in 98% of diarrhoea cases and 60% of those with changes in bowel habit. Constipation was predominantly managed with osmotic laxatives (44%) and stool softeners (36-44%), while anorectal preparations were used mainly for rectal bleeding (14%).
Colorectal cancer was diagnosed in 378 of the patients within 12 months of presentation. Anaemia had the highest positive predictive value (PPV) at 1.8%, followed by rectal bleeding (1.3%). Despite it being common, abdominal pain had a low PPV (0.3%). Median time to diagnosis was 46 days, shortest for abdominal mass (11 days) and change in bowel habit (23 days), and longest for constipation (71 days) and diarrhoea (51 days). Combined abdominal pain and constipation showed a PPV of 1.1%.
“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,” authors wrote.
When investigations were performed, patterns varied widely by symptom. Blood tests were the most common overall, particularly for weight loss (58%), abdominal pain (37%), and diarrhoea (38%). Stool testing was most frequently used for diarrhoea (33%) and change in bowel habit (17%), with nearly one-third including an immunochemical faecal occult blood test.
Imaging was most often used for abdominal mass and abdominal pain. Ultrasound was the most common modality, followed by CT and X-ray, with CT scans used in around 17% of abdominal mass and abdominal pain or constipation presentations.
More definitive investigations were less common and tended to be symptom-driven. Specialist referrals occurred in 60% of rectal bleeding cases and 48% of those with anaemia, while just 16% were referred for abdominal pain and constipation.
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The likelihood of investigation increased substantially when patients had multiple symptoms or repeat visits (OR 3.40). However, disparities were evident: patients aged 80 years and older were significantly less likely to be investigated or referred (OR 0.53), while those from more advantaged areas were more likely to undergo investigation (OR 1.45).
In Australia, colorectal cancer is the fourth most commonly diagnosed cancer and the second leading cause of cancer death, with more than 15,000 new cases and 5000 deaths each year. While incidence has declined in people over 50, rates are increasing in younger populations. Survival exceeds 98% for stage one disease but falls below 15% for stage four, underscoring the importance of early detection.
Although the National Bowel Cancer Screening Program offers free biennial screening for people aged 50 to 74, participation remains low at 41.7% and most cancers are still detected after symptomatic presentation in primary care.
“Although some variation reflects appropriate clinical judgement, inconsistent investigation, especially for non-specific symptoms, indicates potential missed diagnostic opportunities. The low anaemia investigation rate is concerning,” authors concluded.
