Colorectal cancer among top cancers globally

Text and pix by Fathima Riznaz Hafi

Colorectal cancer is one of the top cancers worldwide along with lung cancer and breast cancer. Originating in the large intestine (colon) or the rectum (end of colon), most colorectal cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids). Its exact causes are unknown but people with certain risk factors are more likely than others to develop colorectal cancer.

During a press interview held at Parkway Cancer Centre (PCC) Singapore recently, Senior Consultant Medical Oncology Dr. Zee Ying Kiat shared some facts about this particular cancer; including risk factors, symptoms to look out for as well as precautions on possible relapse.

“The cause of cancer is a genetic mutation takes place which then leads the cells to start dividing in an abnormal fashion and attack normal, healthy tissues and spread. We don’t know what actually causes the genetic mutation; we do however know what can increase the risk of the cancer developing,” says Dr. Zee. 

“In the case of colorectal cancer the main risk factors include age (the risk of colorectal cancer increases from the age of 45 years onwards); gender (men are slightly more at risk than women but women do get colorectal cancer); colorectal polyps, personal history and family history of cancer.”

Modifiable risk factors

There are however ‘modifiable risk factors’ and this is something that is very important to know, he says, explaining that certain lifestyle choices increase the risk of colorectal cancer but fortunately these can be modified to lower the risk. Some of the modifiable risk factors are:

• Smoking: It is not widely known that smoking is actually a risk factor for colorectal cancer; we know that smoking increases risk of heart disease, stroke, lung cancer and oral cancer, but smoking increases the chances of developing colorectal cancer too; therefore one way to prevent colorectal cancer and many other cancers is to stop smoking.
• Alcohol: Consumption of alcohol is another risk. Limiting alcohol intake can help to reduce the risk of colorectal cancer developing. 
• Obesity: It is well-linked to colorectal cancer as well and should be taken very seriously.
• Lack of exercise: If we exercise and maintain a healthy weight it will lessen our chance of developing cancer. 
• Diet: Red meat is linked to development of colorectal cancer; that doesn’t mean that we should avoid red meat altogether but it’s important to lessen the intake of red meat. The key word here is ‘moderation’. Consumption of processed food is an enormous factor for the development of colorectal cancer as well. A diet low in fibre also places us at an increased risk – taking more vegetables and fruits and therefore a higher intake of fibre is known to lessen the risk of developing colorectal cancer.

“Screening for colorectal cancer is a form of prevention as well because if we detect the polyp and it is removed, we prevent the polyp from ever turning into cancer in the future. Obviously there are many things we can do to lessen our chance of developing colorectal cancer; and these are things that are not just helpful for colorectal cancer but for general health as well,” he added. 

Symptoms

“Half the patients with colorectal cancer don’t present symptoms. They are diagnosed because they went for screening – which emphasises the importance of screening! It is known to help save lives and it is predominantly so because it helps to detect cancer at the earlier stage – when treatment is more effective and therefore the outcome is far better,” says Dr. Zee.

If colorectal cancer does cause symptoms, some of them are pain in the stomach, change in bowel habits (constipation or diarrhoea), passage of blood in the stool, nausea, vomiting and tiredness but these are also symptoms that can be the result of non-cancerous illnesses; therefore the best advice for patients with any symptoms is to get themselves checked by their doctor to find out what the cause of those symptoms are, and if indeed a cancer is found, to then have the appropriate treatment for it. 

Screening and treatment

For an individual who does not have a personal or family history of colorectal cancer, the guideline called for screening is to start from the age of 50. There are different methods for colorectal cancer screening; one of them is to look for hidden blood in the stool – this is called a ‘faecal occult blood test’. If taken as a form of colorectal cancer screening it is usually done once every year at the age of 50 onwards.

The alternative method is by colonoscopy which is a method of inserting a lighted instrument with a camera.If the result comes out normal, this is repeated every 10 years but if an abnormality like a polyp is detected then the frequency of screening becomes closer. 

Another form of screening is the ‘CT colonography’ which is a non-invasive form of screening because it involves the use of a CT scanner which can be put through a software package which generates a three-dimensional picture of the inside of the intestine. Whilst this is non-invasive it does have limitations; it is less accurate than a colonoscopy and therefore if pursued and found to be normal CT colonographies have to be repeated every five years. Another limitation of a CT colonography is if a polyp is found the CT scanner cannot remove the polyp so a patient will still have to go through the colonoscopy procedure to get that done.

“If detected in its early stage colorectal cancer is certainly treatable and the rates of cure are high; in stage 1 of the cancer 85-95% of patients are cured by surgery. Even in situations where we are not able to cure the patient from the cancer, the treatment often can make a meaningful difference in their lives; we can prolong their life but prolongation of life on its own is not good enough; it has to be meaningful prolongation – when we prolong their life we must relieve and lessen their symptoms so they go through less suffering related to the cancer,” he said. 

Relapse precautions

“After treatment, there is still a chance that the cancer can relapse; therefore patients are advised to return for follow up on a regular basis with the intention to detect the cancer if it comes back; such that if it relapses we detect it an early level and are then still be able to offer treatment for it,” he said.

When asked if the patients are given a particular time to come back for follow-up, Dr. Zee said, “That really depends on the situation but for colorectal cancer for example, after curative treatment is completed we ask the patient to come back regularly, often every three months for up to about five years. After the five years if there is no cancer we offer the patients the option of not seeing us anymore. Some patients still like to come in, have a chat with us every six months or a year after. Often we use five years but this is very arbitrary.”