By Nicole Tanner

06 June 2017 - 01:07

'At least 70 per cent of colorectal cancers are preventable by changes in dietary and lifestyle habits.' Image (c) melati 411, licensed under CC0 and adapted from the original.
'At least 70 per cent of colorectal cancers are preventable by changes in dietary and lifestyle habits.' Image ©

melati 411, licensed under CC0 and adapted from the original.

Paying attention to your bathroom habits could save you from a life-threatening form of cancer. Nicole Phoebe Tanner, who won the FameLab Hong Kong final, explains.

Is colorectal cancer the same as bowel cancer?

Bowel cancer includes colon and rectal cancer. But technically, the bowel also includes the small intestines, so 'colorectal cancer' is the most accurate term.

What are the signs and symptoms of colorectal cancer?

The general rule of thumb for symptoms of colorectal cancer is 'changes in bowel habits'. Basically, this means changes in the way you normally poo! The poo may change in size or shape, because some colorectal cancers present with elongated or thinned poo, as the cancer creates an obstruction that the poo has to push through. Think of it like squishing icing on a cake. If the inside space of the tube is smaller, the icing comes out thinner. When the inside of the colon is narrowed, the poo becomes slimmer.

When should you call your doctor?

An important sign that definitely warrants a visit to your doctor is finding blood or mucus in your stool. Cancers bleed, and the blood can be found in any form in your poo. The nature of the bleeding can also give you some idea of where the cancer may be located. If the blood is coating the poo, there is a higher chance that the cancer is located near the end of the gut. If the blood is mixed into the poo, the source of bleeding will likely be higher up in the gut, since the blood has had more time with the poo, and the movements of the bowel will mix the two together.

It sounds disgusting, I know! But even if you do find blood in your stool, do not jump to conclusions yet. There are many conditions that cause blood to appear in stool, such as haemorrhoids.

Other changes in bowel habits may include changes in frequency, such as diarrhoea or constipation over an extended period of time, or abdominal pain during defecation. Some patients with rectal cancer may also experience tenesmus, which means feeling the need to poo even right after pooing. That is because the cancer sitting in the rectum tricks the body into believing that there is still poo there, creating a weird sensation.

How can you prevent colorectal cancer?

Colorectal cancer is one of the top killers in many countries – it sneaks up on its victims with little warning. Its symptoms are often subtle and left undetected, so that by the time the symptoms surface, patients are left with very few curative options.

Because of this, many researchers focus on prevention, to kill the killer before it strikes. They are searching for risk factors that make certain groups of people more likely to develop colorectal cancer. These people can then be monitored more closely.

Prevention is divided into two levels: primary and secondary.

Primary prevention targets general populations and aims to prevent diseases before it occurs.

Secondary prevention targets at-risk groups, and aims to prevent diseases in patients with predisposing disorders. These include a hereditary condition called Lynch syndrome, and familial adenomatous polyposis (FAP). Patients with FAP have hundreds of polyps in their colon, which increases the risk of those polyps becoming cancerous.

How can people lower their risk of colorectal cancer?

Primary prevention focuses mainly on lifestyle risk factors such as diet and exercise. Studies show that at least 70 per cent of colorectal cancers are preventable by changes in dietary and lifestyle habits. For instance, exercise has shown to decrease the risk, while obesity and consumption of red and processed meat increases the risk.

However, while dietary restrictions are now widely accepted recommendations, it's not yet clear whether adding dietary supplements or otherwise manipulating your diet makes a difference. Many researchers have tested dietary supplements, such as fibre, antioxidant vitamins, and minerals. But so far, results show that these supplements have little effect in decreasing the risk of colorectal cancer.

So for now, the recommendations remain unchanged: stay as lean as possible within the normal body weight range, and be as active as possible – common sense for many of us.

Who is at risk of colorectal cancer?

People older than 50, and particularly those with a family history of colorectal cancer, are considered to be at higher risk. They are often encouraged to take part in screening programmes.

What's the screening process?

There are different levels of screening, with some procedures more invasive than others.

The first screening involves stool sample collection, a procedure that is inconvenient, but non-invasive and has little to no risks to the patient. A faecal occult blood test is commonly used to examine the stool (occult meaning 'unseen' in this case). It tests for the presence of microscopic or invisible blood in the stool.

The second level of screening is much more invasive. It involves a flexible sigmoidoscopy and a colonoscopy.

A colonoscopy uses a thin flexible tube, about 150 cm long, to examine the inner lining of the large intestines. The scope is guided into the intestines through the anus.

A flexible sigmoidoscopy is a very similar procedure, except the tube is only 60cm long, and just looks at the left colon.

Both these procedures are more dangerous to the patient, as they present risks such as perforation of the intestinal wall, inflammation and the risks associated with anaesthesia.

However, any detected cancers or pre-cancerous masses like polyps can easily be removed during this procedure, so it is both diagnostic and therapeutic.

Why is it important for people to learn about colorectal cancer?

We need to talk about colorectal cancer openly. When it is caught early, there are effective curative treatments, such as surgical intervention.

But when the cancer reaches later stages, or even metastasises (meaning that it spreads to other parts of the body), it becomes much more difficult to treat.

If people know how to detect the symptoms of cancer, such as changes in bowel habits or blood in stool, they can ask for appropriate screening and make more informed decisions about their health.

In my clinical years of medical school, I have met a lot of patients with colorectal cancer. I hear their stories and their lives, and I hear about their sons and daughters, even grandchildren. It is heartbreaking to see that colorectal cancer takes so many lives, and takes so many people away from their families.

Encouraging more people to be more aware of changes in their bowel habits makes cancer easier to catch and treat. Preventing cancer is always better than treating it, so as medical professionals, we need to teach our communities about the warning signs.

Watch Nicole's winning presentation at the Hong Kong FameLab final.

Find out more about FameLab, the international science communication competition, and learn more about our work in science, including opportunities we can offer you.

Nicole will compete in the FameLab International Final. You can live stream the final through the FameLab International Facebook page on Thursday 8th June at 20:30 UK time.

You might also be interested in