The reliance on colonoscopies for cancer diagnosis is unsustainable, and while exciting new and simpler techniques are coming, we need to better use our humble stool test.
The way we diagnose gastrointestinal cancers is about to be revolutionised over the next five to ten years. New non-invasive techniques and technologies are coming, ranging from DNA testing to biosensing the breath – all of which could be done by a visit to the GP. But it is a revolution that can’t come soon enough.
In response to rising public awareness of the need to diagnose these cancers early, and an understandable ‘better safe than sorry’ approach among primary care doctors, modern health systems across the world are now referring millions of people for expensive colonoscopies, when in around 95% of cases the patient won’t have cancer. It is a model that is fast becoming unsustainable.
In Australia the number of colonoscopies performed every year grew by over 20% in just five years to 700,000 in 2012-13, and is forecast to reach 1.1 million by 2020-21. And many of these procedures are unnecessary.
Of Australians whose family history and age put them at only average risk of gastrointestinal cancer, some 18% are being referred for colonoscopies even though they have no symptoms. At the same time, 7% of people at increased risk of bowel cancer, that is those with a risk at least three times the average, aren’t getting colonoscopies at all.
Getting smarter
In the UK the number of day-patient colonoscopies increased by 36% in the five years to 2015. The number of urgent referrals for suspected lower gastrointestinal cancer increased by a massive 78% over that time, but the proportion of those who were eventually diagnosed with cancer fell from 6.4% to 4.1%.
The overuse of colonoscopies isn’t just a problem of cost and waste of resources, it is also harmful. Based on meta-analysis of published rates of complications in Australia (here and here), every one million colonoscopies for people without symptoms would result in 80 deaths, 1,400 bleeds and 680 bowel perforations to diagnose 2,910 cancers.
We need to be smarter at selecting the higher risk patients that need to be referred for a definitive diagnostic test. On average, the life-time risk of colorectal cancer is around 5%, but the risk for many people will be substantially below that. For example, the 25% of the population most at risk are 20 times more likely to have cancer than the 25% who are among the lowest risk.
The best approach here is to boost the diagnostic capacity of general practitioners so they can make better use of existing effective non-invasive tests. The most obvious of these are stool tests to screen out people who aren’t at increased risk of bowel cancer.
The National Bowel Cancer Screening Program, in which people aged over 50 are regularly sent testing kits for submitting a stool sample, is a highly cost-effective form of screening, but it is hampered by a low uptake. Of the 2.6 million people sent kits in 2014-15, only 39% participated. If the response rate could be increased to 50%, the savings on colorectal cancer control would amount to $2 billion by 2030.
Involving primary care
One key reason the response rate is so low is a simple one – squeamishness – but it isn’t helped by the program largely bypassing primary care. A visit to the GP should be an ideal opportunity to discuss routine screening. And the benefits are huge. A bowel test and early diagnosis can reduce your risk of death from bowel cancer by 15% or more.
Beyond the short term, the way we screen and test for cancers like gastrointestinal cancer is set to change dramatically. These new techniques include screening for people when there are no symptoms and tests for those with symptoms.
Biomarkers
Ongoing research into identifying biomarkers for cancer, like individual proteins or cancer DNA, could allow us to diagnose cancer much earlier. Many biomarkers for different types of gastrointestinal cancer are in development. First, we need to know how accurately they diagnose cancer, either in people before they develop symptoms or with symptoms that might be due to cancer. Once we are sure these tests are accurate they could be used through stool or blood sampling, all of which could be administered through primary care.