Colorectal cancer is the third most commonly diagnosed cancer. — 123rf.com
Colorectal cancer (CRC) is a serious disease of the colon or rectum – the main parts of the large intestine – and affects millions worldwide.
Closely linked to diet and lifestyle, CRC holds a grim distinction: it is the third most commonly diagnosed cancer and the second leading cause of cancer deaths globally.
In 2020, there were 1.93 million new cases and 935,000 deaths. By 2040, this number is projected to rise to more than 3.2 million new cases a year, with the disease increasingly affecting younger people. Yet CRC develops slowly – often over 10–15 years – as normal cells gradually transform into invasive tumours.
Understanding this slow, insidious development is not merely academic; it is the key to prevention and early detection, offering tangible hope to informed people in the fight against this stealthy, prevalent disease.
My involvement with CRC started when I became aware of the seriousness of the disease, which eventually claimed the life of a very dear old friend.
His situation prompted me to take a faecal immunochemical test (FIT) in France, which then led to a colonoscopy, during which a 25 mm pre-cancerous pedunculated (stalk-like) polyp was removed.
This type of abnormal growth is also known as an advanced adenoma. The large size of the polyp meant that it had a statistical 26%-30% chance of becoming cancerous, and this high probability was confirmed by the subsequent biopsy. You would not cross a road if the chances of getting killed are as high.
Statistics
Despite the seriousness of the disease, CRC statistics are a minefield to unravel.
At first glance, the average global incidence rate looks small: about 19.5 cases per 100,000 people (23.4 for men, 16.2 for women) – or just 0.0195%.
That rate is similar to tuberculosis or food poisoning from Campylobacter infections. Figures like this may seem too small to worry about.
By comparison, dengue fever in 2021 had an average incidence of 752 per 100,000 people (0.75%) — almost 40 times higher than CRC. Malaria in 2023 was even greater, at 6,040 per 100,000 (6.04%), more than 300 times higher than CRC.
Diagnostics change the stats
However, the CRC statistical picture changes dramatically with age and diagnostics.
After 50, incidence rates triple to more than 60 per 100,000 (0.06%) in many developed countries. Between ages 60 and 69, it more than doubles again to about 160 per 100,000 (0.16%). Above 70, rates exceed 200 per 100,000 (0.2+%). And that is where the statistics stop, at least for age groups above 50.
Excessive alcohol consumption is one of the lifestyle choices that can put people at higher risk of getting colorectal cancer. Photo: ELINA SAZONOVA/Pexels
The next logical step is to look at incidence among people with positive FIT results. These figures cover only those who took the test and tested positive.
Importantly, this includes detection of pre-cancerous growths such as adenomas — the origin of more than 75% of CRCs. Rates vary greatly with age, and test results also depend on the cut-off sensitivity used, as discussed later.
Among FIT-positive individuals, on average, 47.8% have adenomas, 25.3% have advanced adenomas, and 5.1% already have CRC.
These averages mask strong age effects, since the stats from older people drive much of the data. Across all ages, however, men are more affected: 58.1% of FIT-positive men have adenomas, compared with 41.9% of women.
Breaking down FIT-positive statistics by age, the statistics are a little disparate as they are gathered from various countries with different methods of reporting data.
But as far as I can determine, for people between the ages of 50 to 59 with a positive FIT, 28%-45% have adenomas, 10%-20% have advanced adenomas, and 1.5%-6% have CRC.
For ages 60–69, a positive FIT result means 40%–50% have adenomas, 25%–30% have advanced adenomas, and 4.5%–9.5% have CRC. Above 70, adenomas occur in more than half of FIT-positive people, advanced adenomas in over 30%, and 7.5%–11% have CRC.
These FIT-positive figures are alarmingly higher – by many orders of magnitude – than the 0.0195% incidence rate seen in the general population.
This stark contrast is a powerful, irrefutable warning that the risks of individuals with positive FIT results are very significantly worse compared to the general population. In short, any positive FIT result warrants urgent and serious medical investigation.
Cut-offs
Another thought-provoking and probably important point is the cut-off sensitivity of FIT analyses. In France, the cut-off is 30 micrograms of blood in a single gram of stool material.
This is pretty sensitive and will detect relatively tiny amounts of blood in the colon. Other countries may use much higher cut-offs; for example, parts of the UK use a cut-off of 80 mcg.
A higher cut-off means that a positive FIT is more certain to be indicative of significant colon problems or CRC (as more blood has been detected), but it may also mean detection can be late.
Diets high in processed food can cause an increased risk of developing colorectal cancer. Photo: TIM SAMUEL/Pexels
Ultimately, it comes down to costs. A well-funded health system will want to use a low cut-off, even though there may be more false positives.
A high cut-off will certainly miss early colon issues but result in less post-test interventions and may be more cost-effective.
In my case, I had submitted FIT samples in the UK every two years and the latest test was done in April last year. As always, the result was negative, with a letter stating that the next FIT will only be required in 2026.
This means that all the UK FIT samples had missed the large pedunculated polyp for several years, as such polyps tend to grow at a rate of well under 1.3 mm a year. In fact, the polyp would already have been considerably larger than 10 mm many years ago, a size where removal is considered medically prudent.
So taking a FIT does not necessarily mean that all is fine. In my case, I had no symptoms at all, and was somewhat shocked and initially irritated by the French FIT result.
However, seeing the condition of my friend made me decide to follow through with all the proper procedures, with the outcome as described earlier.
Therefore, if you take a FIT, it may make sense to check that it uses a low cut-off. That detail may be crucial.
What causes CRC?
Apart from age, and the possible consequences of age-related wear and tear in the intestines, the main causes which can provoke CRC are well-known. They include the following:
Lifestyle and environmental factors:
> Diets high in processed food and red meats and low in fibre, fruits, and vegetables.
> Obesity and being overweight increase CRC risk.
> Physical inactivity contributes to higher risk.
> Smoking and excessive alcohol consumption are also established risk factors.
Medical conditions:
> Inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis raise the risk.
> Insulin resistance and diabetes also contribute to CRC.
> Genetic conditions such as Lynch syndrome, familial adenomatous polyposis, MUTYH-Associated Polyposis, Peutz-Jeghers syndrome, etc, are causes of CRC
Microbiome influence:
> Certain bacteria, like “Streptococcus gallolyticus” and some strains of “Escherichia coli”, have been associated with colorectal cancer, suggesting that gut microbiome plays a role in carcinogenesis.
CRC incidence is rising worldwide, most sharply among younger people not traditionally considered at high risk. Possible culprits include ultra-processed foods, pesticides, red and processed meats, food contamination from pollution, forever chemicals, microplastics, synthetic additives, etc. All may play a role, yet governments and industry show little urgency in identifying or eliminating these causes. Whatever the precise triggers, diet is central: CRC is a disease majorly influenced by what we ingest.
As a comment, if governments and institutions are slow to take action, the responsibility falls on us to make sure that what we and our families eat is truly wholesome and healthy – not just well-marketed or attractively packaged foods packed with synthetic additives and processed gunk that could increase the risk of CRC later in life.
However, in all cases, the ultimate underlying cause is genetics. Evidence of this is that inherited syndromes such as those described earlier all sharply increase CRC risk, as does any strong family history of the disease.
To be crystal clear, colorectal cancer is always the outcome of major genetic damage in the cells of the colon. And these cancer causing mutations are strongly influenced by our diet, lifestyle, and/or pre-existing genetic traits.
One misconception some people may have is that although CRC is common, it is also an easily “curable” cancer. Nothing is further from the truth. CRC is the third most common cancer worldwide but the second biggest cause of cancer deaths, after lung cancer. It is true that CRC is more treatable in its earlier stages (like most cancers), but once the disease has progressed past Stage 3, the mortality rate is over 85%.
The next part explores the sobering, cautionary factors involved in the biological progression towards the development of CRC.
The views expressed here are entirely the author’s own
