Colon cancer is the third most common cancer and the fourth most common cause of cancer-related death worldwide. It is a complex disease linked with both genetic and lifestyle factors.

To minimise suffering and death, most countries have screening programmes offering tests to prevent the disease or detect it as early as possible.

Luckily for us in Bermuda, we have sophisticated systems in place to ensure screening of the highest quality along with extensively trained experts to deliver it.

Still, when the patient’s GP says it is time for their first routine screening, there are naturally concerns. So, to calm any anxiety or fear, I am going to answer some of the most common questions I hear when the patient is passed on to us to begin the screening process.

Can I have cancer if I feel well and have no symptoms?

In short, yes. The majority of colon cancers grow from small lesions in the colon called polyps. Unless the polyps are very large and bleed, you will feel nothing. Visible changes may appear only after the cancer has already developed to an advanced stage, and that is obviously what we really should avoid. Signs of cancer may include rectal bleeding, blood in your stools, abdominal pain, unexpected weight loss, anaemia or a change in bowel movements.

Over the past few years, we have seen an increasing amount of young and apparently healthy people with colon cancer showing up on their first routine inspection of the colon. This troubling finding motivated the American Cancer Society to change its guidelines and recommend average-risk screening to begin at age 45 instead of 50.

Do I have a choice of screening techniques?

There are various options, each with pros and cons. When weighing them up, it’s important to give serious thought to the difference between prevention and detection. Prevention is possible only through a procedure called colonoscopy, which identifies precancerous lesions and removes them before they can grow into cancer. Detection identifies cancer that has already taken hold in your body.

Colonoscopy: it cannot be overemphasised that this remains the only method to prevent and treat colon cancer at the same time, and it’s the No 1 recommendation of all gastroenterological and cancer societies worldwide. Sadly, some countries — even including Britain, believe it or not — do not have the facilities and/or finances to make colonoscopy their universal first line of colon cancer defence, but Bermuda does.

But what’s the process?

Frst, there will be a thorough office consultation to build up a clear understanding of your individual situation. Normal-risk people should have a colonoscopy every ten years while those with a family history of colon cancer or advanced adenomas should be screened at shorter intervals, to be discussed at the office.

The endoscopist’s team will then book you in as an outpatient at King Edward VII Memorial Hospital to take a remarkably detailed look at your whole colon and rectum from inside your body — using a long, flexible tube with the outer diameter between 9.5mm and 12.5mm and a tiny camera at its tip to find and remove polyps or cancer. You are highly unlikely to feel a thing before, during or after the procedure as you will be given mild but sufficient sedation.

By the way, here in Bermuda, the endoscopy unit where the procedure is done is located inside the operating room, which gives the patient the luxury of a dedicated anaesthesiologist and the superb operation room nursing team, followed by a nice cup of tea when you wake up in the operating room’s pleasant recovery room!

Stool-based tests: perhaps best described as a better-than-nothing solution for people who decline colonoscopy, these at-home tests are pretty easy and inexpensive to use to find hidden blood in stools. They are sent for laboratory analysis and if the results aren’t normal, it will require further investigation by your healthcare provider — and you will probably end up seeing me or a colleague anyway.

If selected, these tests — fecal immunochemical and fecal occult blood, to give them their full titles — must be done every year by normal-risk people.

Cologuard®: this finds abnormal cell parts and DNA from colon cancers and polyps as well as testing for blood in stools. This combination helps because colorectal cancer or polyp cells often have DNA changes in certain genes, and cells with these mutations can get into stools, where they may be spotted.

Cologuard is the only such combined test available at present and may seem appealing because you can do it at home then send it to a lab. However, stool tests detect only a minority of cancers or advanced adenomas, with a detection rate of 42 per cent for Cologuard and up to 24 per cent for a fecal immunochemical test. Other question marks about Cologuard include an arguable cost-benefit ratio and lack of scientific information on long-term outcomes.

Flexible sigmoidoscopy: countries with financial limitations for preventive medicine offer this method instead of colonoscopy for average-risk patients.

The endoscopist uses a shorter tube with a tiny camera on the end to check the rectum and the lower end of the colon — actually, only the final two feet of the colon’s six feet — for polyps and cancer. If a polyp or abnormality is found, a colonoscopy may have to be performed. If annual stool tests are negative for blood, normal-risk people can have a sigmoidoscopy every five years.

Computed tomographic colonography: the CTC takes pictures of your colon and rectum using a special machine. Some patients may be interested because it doesn’t require sedation. It is an acceptable alternative to colonoscopy for evaluating the colon proximal to an obstructing lesion, or following a failed colonoscopy with continued need to evaluate the colon. It can also be considered in patients who cannot undergo colonoscopy, or choose not to for one reason or another. However, the CTC will not detect flat lesions or polyps under 6mm. Also, if a polyp is found, you will need a colonoscopy anyway. But if the CTC route is chosen, normal-risk people should undergo it every five years.

Can I have colon cancer if there is no family history of it?

Although people with a family history of colon cancer or polyps have a higher risk, the vast majority of colon cancers develop in people who have no family history. These are called sporadic cancers.

Roughly one in five young adult-onset colorectal cancers is caused by a genetic abnormality and, among those with a detectable hereditary condition, half the young adult-onset patients will have Lynch Syndrome, which carries an increased risk of endometrial, gastric, ovarian, small bowel, renal pelvis and ureteral cancers.

Other genetic abnormalities include Familial Adenomatous Polyposis, the second-most common hereditary cause for young-onset colorectal cancer. Patients with that condition develop literally hundreds to thousands of colorectal polyps and have an almost 100 per cent risk of developing cancer by the age of 40.

Another genetic condition is MYH-associated Polyposis, whose typical age of polyp onset is in the patient’s forties. MAP’s polyp burden is generally under 50 polyps, but the cancer risk is increased significantly, with most cancers arising under the age of 60.

Naturally, these patients will be managed with extreme individualised care and will have increased screenings.

Should some people not be screened? And when should screening be stopped?

Most international guidelines recommend against routine screening from 76 to 85 years old, and advise not to screen beyond 85 for early detection of adenomatous polyps and colorectal cancer in average-risk patients. This is based on modelling data that takes into consideration a lifetime of screening, polyp growth time and expected longevity. Moreover, the highest rate of serious complications during and after colonoscopy occurs at these advanced ages.

It may sound a bit blunt, but the use of screening colonoscopy is inappropriate in people who are not expected to live longer than ten years. The presumed benefits of early cancer detection, in terms of improved survival and quality of life, must be balanced against possible negative consequences, such as no improvement of disease-specific mortality, and also against underlying life-expectancy concerns.

Decisions about screening need accurate estimation of individual benefits and risks. General health and functional status as well as comorbidity are better indicators of expected life span than chronological age alone.

How can I decrease my risk of developing colon cancer?

Our Western lifestyle — higher calorie, lower fruit and vegetable-based, meat-predominant diet, higher body mass index and decreased physical activity — may contribute to the rise of young-onset colorectal cancer. And excessive sedentary time — measured in hours of watching television or surfing the web or gaming — is also associated with an increased risk of young-onset cancer, particularly rectal.

On there other hand, no smoking and limited drinking combined with eating well and exercising to achieve a healthy weight are associated with lower risk.

Although people may perceive that having an increased genetic risk means they are powerless against this predisposition, a healthy lifestyle can still reduce colorectal risk.

On top of this, substantial evidence has shown that the risk of colorectal cancer can be greatly reduced through colonoscopy to remove precancerous lesions, which in turn may reduce the influences of lifestyle and genetics.

And best of all is a combination. Data from the large population-based DACHS study in Germany, which began in 2003, proved that adherence to a healthy lifestyle along with colonoscopy in the preceding ten years led to a reduced relative risk in both men and women.

So, be active, eat healthily and get screened. While any screening is better than no screening at all, we should feel very fortunate here that in colonoscopy we have the best possible screening — and it is generally covered on your insurance.

• Suraia Boaventura Barclay, MD, is a Fellow of the American Gastroenterological Association, and is on its International Education sub-committee. She got her MD from the Federal University of Bahia, Brazil. After postgraduate study at the University Hospital Eppendorf, Hamburg, under the world-renowned professor Nib Soehendra, she was awarded her Doctorate in Clinical Gastroenterology