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Cancer: Why is it so confusing?

It is one of the top killers in the world, but still widely misunderstood. Parkway Cancer Centre’s Dr Foo Kian Fong explains the basics of cancer.

Cancer is one of the top causes of death around the world. In 2015, it accounted for nearly nine million deaths – about one in six deaths. According to the World Health Organization, the top five cancers that result in death are lung, liver, colorectal, stomach and breast cancers.

In Singapore, it was the top cause of deaths – almost 30 per cent – in 2015. According to the Singapore Cancer Registry, between 2011 and 2015, the top three cancers diagnosed among men were colorectal, lung and prostate cancers. Among women, it was breast, colorectal and lung cancers.

By some estimates, one out of every four or five people is likely to get the disease in his or her lifetime. The risk increases with age, though constant improvements in medical technology, treatment and cancer care will also mean that people are more likely to survive.

A problem of division

Cells need to grow and divide to produce more cells to keep the body healthy. Sometimes, however, this process goes wrong.

The division of cells is controlled by genes, which are located in the cell nucleus. They give the cell instructions on how to divide and how long to live, but if these instructions contain errors, it can result in mutations.

For example, it may divide uncontrollably, producing unnecessary cells that form a tissue mass called a tumour. The abnormal cells can also invade nearby tissues or travel to other parts of the body, crowding out and destroying normal tissues. When this spread – called metastasis – happens, cancer results.

Not all tumours are cancerous. Some are benign, that is, the cells do not spread to other parts of the body. Such tumours can be removed, and in most cases, do not return. But some tumours may be malignant, that is, the cells do spread.

Causes of cancer

There are many factors that can cause or increase the risk of cancer occurring in each person. One is genetic make-up, which can pre-dispose an individual towards developing the disease.

Another is the action of external carcinogens, which are agents or substances that cause cancer. Interaction between these carcinogens and genes can result in cell damage and changes that lead to cancer.

Carcinogens include ultraviolet (UV) rays, radiation from X-rays, asbestos, infections caused by particular viruses, certain toxins found in chemical products – and tobacco.

Tobacco, however, is by far the most common cause of cancer. Smoking – including passive smoking – can lead to lung, throat, mouth, pancreas, bladder, kidney, stomach and liver cancers. Tobacco smoke is made up of thousands of chemicals, many of which are carcinogenic. More than 80 per cent of lung cancer cases worldwide are caused by tobacco.

Lifestyle and diet can also affect the risk of getting cancer. Insufficient intake of fruit and vegetables, or high intake of salt or alcohol, can increase the risk.

Lowering the risk

While there is no way to completely prevent cancer, there are many ways to reduce the risk of getting the cancer.

• Stop smoking: Do not start, or stop if you have been smoking. No matter what age you are at, quitting can lower the risk of getting lung cancer. Try to avoid breathing in second-hand smoke, as passive smoking can increase the risk of lung cancer, even for non-smokers.
• Eat healthily: Eat less meat and processed foods. Almost a third of cancers are related to nutrition and weight.
• Drink less alcohol: Do not have more than one to two drinks of alcohol a day.
• Stay active: Get at least 30 minutes of aerobic exercise a day.
• Keep out of the sun: Help lower the risk of skin cancer, which often affects exposed parts of the body, such as the face, hands, forearms and ears. Cover up with a cap and clothing, and use a strong sunscreen.
• Get immunised: Vaccination can help prevent cancers linked to viral infections, such as Hepatitis B, which can lead to liver cancer, and HPV (Human Papillomavirus), which can lead to cervical and other genital cancers.
• Get screened: Regular screening and self-examination raises the chances of discovering a cancer early, which in turn improves the chances of successful treatment.

Spotting the signs

On top of regular screening, looking out for unusual changes in your body can help in early detection of cancer. While the signs listed here do not always mean you have cancer, it is good to be prudent. If they persist, consult your doctor immediately. Even if they do not arise from cancer, they could indicate the presence of other diseases or issues.

• A sore on the skin, vagina, any oral cavity, or other part of the body that does not seem to get better.
• Unusual bleeding or discharge, such as blood in the phlegm or stool, abnormal vaginal bleeding, or bloody discharge from the nipple.
• A thickening lump in the breast, testicles, lymph nodes or soft tissues.
• Change in bowel habits or bladder function, such as chronic constipation or diarrhoea, pain when you urinate, urinating more or less frequently, blood in your urine, or a significant change in the size of your stool.
• Persistent cough or hoarseness.
• Indigestion or difficulty swallowing your food.
• Changes in a wart or mole, such as a sudden change in the colour, shape or size of a wart or mole on the skin.
• Unexplained weight loss, such as weight dropping by five kg or more even though you are not on a diet.
• Back pain, or tenderness or discomfort in your lower back or hip bones.
• Fever and extreme fatigue.

Screening: When to go

Go for regular screening of your skin, mouth, colon and rectum. Men should include screening of prostate and testes, while women should include cervix and breast cancer screening.

Breast cancer screening (women)

39 years and below: Monthly breast self-examination

40 to 49 years: Monthly breast self-examination, annual screening mammography

50 years and above: Monthly breast self-examination, two-yearly screening mammography

Cervical cancer screening (women)

Above the age of 25 and sexually active: A Pap smear test every three years.

Colorectal cancer screening (men & women)

50 years and above: Annual faecal immunochemical test (FIT) and a colonoscopy every 10 years.

Those with higher risk of colorectal cancer: Start screening earlier and get a colonoscopy once every three years.

Written by Kok Bee Eng