Interview with A/Prof Tan Ker Kan: Tackling Colorectal Cancer, the Top Silent Killer in Singapore

Tuesday, February 21, 2023
Interview with A/Prof Tan Ker Kan:
Tackling Colorectal Cancer, the Top Silent Killer in Singapore

Cancer statistics in Singapore have shown that colorectal cancer tops the list of reported cancer for men and comes in second for women, after breast cancer.

Often termed as a “silent killer”, the symptoms for colorectal cancer usually only appear when the cancer has advanced to a later stage.

We speak to Assoc Prof TAN Ker Kan, NUS Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, to understand more about this silent disease, as well as his thoughts on tackling this prevalent cancer.

Prof Tan-Ker-Kan
More about A/Prof Tan Ker Kan
As both surgeon and health services researcher, A/Prof Tan’s primary research interests span the entire spectrum of colorectal cancer journey. On top of his academic appointments in NUS, A/Prof Tan is the Head and Senior Consultant in the Division of Colorectal Surgery, Department of Surgery, at National University Hospital. He also holds several administrative leadership roles, which includes Vice Chairman of the NUH Medical Board, Assistant Dean of the Yong Loo Lin School of Medicine and Head of the Division of Surgical Oncology (Colorectal Surgery), at National University Cancer Institute, Singapore (NCIS), and more.

Colorectal cancer – the top reported cancer

Has colorectal cancer always been this prevalent? What are your views of the recent trends of colorectal cancer in Singapore?

A/Prof Tan: “Based on the data from the National Registry of Diseases Office (NRDO) from the Ministry of Health, the incidence of colorectal cancer has been rising over the past few decades but has rather plateaued in recent years. It is likely that the number of patients with colorectal cancer will increase with a greying population.”

Are there any behavioural / thought patterns or contributing factors you have noticed, which could have given rise to the trend(s) observed?

“Some have purported that the rising incidence of colorectal cancer over the past few decades has been due to the “Westernisation” of our diet” with higher consumption of processed food, red meat, and also rising incidence of obesity.

However, I think the plateauing of colorectal cancer is a good sign and I attribute this to the enhanced awareness of this disease through the Ministry of Health/Health Promotion Board’s screening effort as well as the increased adoption of screening tools such as the faecal immunochemistry test kits and colonoscopy.”

Development of colorectal cancer and its symptoms

We understand that in most cases, colorectal cancer starts as a growth (called polyps) on the inner lining of the colon. Depending on the type of polyps, some polyps can become cancerous over time – a process estimated to take five to ten years. Asymptomatic polyps are present in up to 25% of individuals at age 50 and the prevalence increases with age.

As the cancer develops through the stages, it penetrates the lining and grows into the inner wall and thereafter through the wall of the colon. At a later stage, it spreads to the lymph nodes and eventually to the other parts of the body.

What are the symptoms and at what stage of the cancer does the patient usually exhibit these symptoms?

4. pain image
“In the early stages, minimal symptoms are present. It is not uncommon for anyone of us to have occasional tummy upset or change of bowel habit. As the cancer enlarges, it then results in more obvious symptoms. These include persistent abdominal pain, passage of bloody stools, constipation, decrease in caliber of stool or symptoms of anaemia (due to persistent blood loss). As the cancer is bigger then, it is likely that the cancer is of more advanced stage.

However, it is difficult to correlate symptoms to the stage of cancer upon diagnosis as different patients have varying threshold of seeking medical advice and the “biology” of the cancer also plays a role in the stage of the cancer when it is diagnosed.”

Is there an estimate on the duration taken for the advancement of each cancer stage?

“Unfortunately, it is difficult to predict or estimate the duration taken for the advancement of each cancer stage.”

Individuals recommended for screening and the screening methods

Who should screen for colorectal cancer and when should screening start?

“Screening is recommended for individuals at the age of 50 without notable risk factors. 

For those who have increased risks, screening should start earlier depending on the risk category one is in. Contributing factors to one’s risk levels include having a family history of colorectal cancer, as well as a personal history of colon polyps or ulcerative colitis (inflammation of the bowel).”

What are some ways we can screen for colorectal cancer?

5. Colonoscopy
“The gold standard for the detection of colorectal cancer is through colonoscopy. In the event abnormal growths or polyps are found during the procedure, they are often removed at the same setting. If tumours are detected, tissue samples will be extracted to confirm the underlying diagnosis. The procedure takes around 20 to 30 minutes.

While effective, it is shunned by many for reasons such as being a hassle due to the need for bowel preparation, the inconvenience of undergoing the procedure, its invasiveness, and cost.

There are also other screening methods which are non-invasive and do not require bowel preparation, such as the Fecal Immunochemical Test (FIT). This detects the presence of blood in the stool which may not be visible to the human eye. The reason in doing so is because as stool passes through the colon, it may come into contact and damage the larger colorectal polyps, causing them to bleed into the colon or rectum.

Considered a non-invasive test, the FIT is performed by the individual themselves at their own convenience and in the comfort of their own homes.”

How effective is the FIT as a screening method?

“If the individual is compliant to performing the yearly test for stool occult blood by using 2 FIT kits, it has been shown to improve the outcomes for patients with colorectal cancer than those who did not screen. However, many individuals are not compliant to perform the tests annually after receiving an index negative test result.

This is because there is the chance of a false negative result from individuals using the FIT kits when they sample the stool.

Any individual with a positive FIT will be advised to undergo a colonoscopy for further evaluation. In Singapore, the probability of anyone with a positive FIT that is subsequently diagnosed with colorectal cancer is around 4%, whilst around 40-50% of these individuals will have colonic polyp(s).”
6. FITkit

Curbing of colorectal cancer through lifestyle choices

What are some lifestyle choices we should avoid, in order to curb colorectal cancer?

“I personally think that smoking and obesity are clear factors that everyone of us should avoid. Not only does it reduce the risk of developing colorectal cancer, it reduces the risks of many other serious diseases such as heart attack, stroke and developing other cancers. 

Other factors that one should avoid include excessive alcohol use, excessive red meat and processed meat diet, and lack of exercise.”

What is one fact, message or advice about colorectal cancer that we should pass on to our friends and loved ones?

“Colorectal cancer is a preventable cancer and screening in colorectal cancer has been shown to be beneficial to the individual and to our loved ones. Many patients who are diagnosed with colorectal cancer lamented on the numerous missed prior opportunities that they could have acted earlier.”

FIT kits made accessible for the NUS community from 27th March 2023

Recognising the prevalence of colorectal cancer in Singapore, UHC has partnered the Singapore Cancer Society (SCS) to be one of the FIT kit collection centres for eligible NUS staff and their dependents.

More details about the collection may be found here.

  • Home
  • Resources
  • Articles