Screening Tests to Prevent Cancer - Colonoscopy & Pap Smear

Contributed by: Dr Zee Ying Kiat

Screen & protect

Early detection of cancer is important. If a cancer is found in its early stages, it can greatly increase the chances of successful treatment. There is a wide range of tests that can be done to check for cancer cells in a patient’s body. People of a certain age, especially those who are at high risk of getting cancer, are advised to go for regular screenings.

But screening tests can sometimes also help in preventing cancer from developing in the first place.

Parkway Cancer Centre’s Dr Zee Ying Kiat looks at two screening tests that can help you prevent cancer.


Large intestinal or colorectal cancer is the most common cancer in Singapore, with about 1,200 new cases diagnosed each year. At the same time, it is also one of the most treatable and preventable forms of cancer if it is detected early.

A large majority of colorectal cancers arise due to adenomatous polyps, gland-like growths which develop on the mucous membrane lining the large intestine.

Adenomatous polyps generally do not display any symptoms and they are present in as many as one in four men by the time they turn 50. The prevalence increases with age.

The time taken for these polyps to become malignant is usually between five to 10 years. This means that colorectal cancer has a significant period of detectable premalignant phase before the polyps become cancerous.

One of the most common screening tests for colorectal cancer is a colonoscopy. This is when a thin, flexible tube known as a colonoscope is inserted through the rectum to allow doctors to look at the inner lining of the patient’s large intestine.

A colonoscopy can be done within 15 minutes. Before the procedure, the patient’s bowel must first be thoroughly cleaned. This is usually done the day before or the same morning as the colonoscopy. The patient will be given medication to induce diarrhoea.

Patients usually feel only a little pain although mild sedation is typically given to relieve the patient’s discomfort or anxiety. Most patients can resume their regular diet later in the day and there is hardly any down time.

Most polyps can be removed during colonoscopy, avoiding the need for surgery to remove the growths.

Pap test

A Pap test, also called a Pap smear, is a simple procedure to test for cervical cancer where the doctor gently brushes cells from the narrow neck of the cervix and sends the sample to the laboratory to examine for any changes in the cervix, which is the opening of the uterus or womb.

Two days before the Pap smear, avoid sexual intercourse, douching, or using any vaginal medicines or spermicidal foams, creams or jellies as these may wash away or obscure abnormal cells. Avoid scheduling a Pap test if you are menstruating.

The test takes only a few minutes and is usually not painful although it can be a bit uncomfortable as an instrument is inserted into the vagina to hold it open so that the cervix can be seen clearly. A plastic spatula and small brush are used to collect cells from the cervix.

The cells are then tested and results are usually out in a few days up to a couple of weeks.

The Pap smear detects pre-cancers before they become invasive cancer. Pre-cancers can be treated, preventing cervical cancer before it begins. Experts say that cervical cancer is one of the most easily preventable cancers and the best way to do this is to get a Pap test done regularly.

Go get tested!

While colonoscopy and Pap smear can help prevent cancer, other tests for cancer such as mammograms, blood tests and CT scans are equally important in the fight against cancer.

Very often, cancer which is detected early can be nipped in the bud and patients go on to live normal lives after that.

Many studies over the years have consistently shown that a patient’s chance of survival greatly increases when cancer is detected early. With late detection, cancer cells may have a higher chance of spreading to other parts of the body, complicating the treatment process.

For example, studies on bowel, breast and ovarian cancers have all shown that more than nine in 10 patients with an early diagnosis of these cancers survive beyond five years, compared with only about one in 10 for those diagnosed with the most advanced stage of the cancer. 

Screening: Who and when


  • If you have no high-risk factors, start screenings from the age of 50 and do a colonoscopy every 10 years.
  • Those who are at high risk of getting colon or colorectal cancer should start screenings at an earlier age and get a colonoscopy done once every three years.
  • People who are at a very high risk may need to do a colonoscopy every year from as young as their teens.
  • Can be fully paid for using Medisave.

Pap test (Pap smear)

  • Women above the age of 25 who have been sexually active even once should do a Pap test every three years.
  • The Singapore Cancer Society offers free Pap tests; polyclinics and certain general practitioners (GPs) offer it at a subsidised rate or even for free for those who are eligible.

Written by Ben Tan

POSTED IN Cancer Prevention
TAGS cancer screening, cancerous polyps, colonoscopy, common cancer, mammogram, pap smears, prevent cancer
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