Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. One defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs; the latter process is referred to as metastasis. Widespread metastases are the primary cause of death from cancer.

Cancer arises from the transformation of normal cells into tumour cells in a multi-stage process that generally progresses from a pre-cancerous lesion to a malignant tumour. These changes are the result of the interaction between a person’s genetic factors and three categories of external agents, including:

• physical carcinogens, such as ultraviolet and ionizing radiation;

• chemical carcinogens, such as asbestos, components of tobacco smoke, alcohol, aflatoxin (a food contaminant), and arsenic (a drinking water contaminant); and

• biological carcinogens, such as infections from certain viruses, bacteria, or parasites.

The incidence of cancer rises dramatically with age, most likely due to a build-up of risks for specific cancers that increase with age. The overall risk accumulation is combined with the tendency for cellular repair mechanisms to be less effective as a person grows older.

Cancer is a leading cause of death worldwide, accounting for nearly 10 million deaths in 2020, according to the International Agency for Research on Cancer which is the cancer research agency of WHO. The most common in 2020 (in terms of new cases of cancer) were:

• breast (2.26 million cases);

• lung (2.21 million cases);

• colon and rectum (1.93 million cases);

• prostate (1.41 million cases);

• skin (non-melanoma) (1.20 million cases); and

• stomach (1.09 million cases).

The most common causes of cancer death in 2020 were:

• lung (1.80 million deaths);

• colon and rectum (916 000 deaths);

• liver (830 000 deaths);

• stomach (769 000 deaths); and

• breast (685 000 deaths).

Apart from the above types of cancer, leukaemia is the most common cancer diagnosis in children and teens, accounting for almost 1 out of 3 cancers, according to the American Cancer Society.

Overall, however, childhood leukemia is a rare disease. Leukaemia is a cancer of the early blood-forming cells. Most often, leukaemia is a cancer of the white blood cells, but some leukaemias occur in other blood cell types.

Cancer Incidence in Singapore

Cancer cases have been rising over the years, and the number of people living with cancer will continue to increase.

During the period from 2015-2019, 78,204 cancer cases were reported in Singapore and 49% and 51% of those cases were reported in males and females respectively, according to the Singapore Cancer Registry Annual Report 2019.

Three most frequent incident cancers reported for males and females in this period are:

Males: colorectal (6,436 cases/16.9%), prostate (5,875 cases/15.4%) and lung (5,218 cases/13.7%)

Females: breast (11,805 cases/29.4%), colorectal (5,253 cases/13.1%) and lung (3,074 cases/7.7%).

According to the Singapore Cancer Society, only approximately 5 to 10 per cent of all cancers are directly caused by inherited genetic mutations. Certain cancers are preventable and many cancers are treatable and curable, especially with effective treatment in the early stages to curb the spread of cancer cells.

Screening helps to detect early signs of cancer or pre-cancerous conditions before any symptoms appear. By the time symptoms like tumours occur and cancer diagnosis is confirmed, the disease is often at an advanced stage.

Earlier detection and treatment of early stage cancer are typically less invasive as compared to more advanced cancers.

Receiving less cancer treatment also means less costs incurred and shorter recovery time.

The National Cancer Centre Singapore has advised that cancer screening needs to be appropriate, evidence based and recommended by accepted guidelines.

The Singapore Ministry of Health has published guidelines to help guide physicians and the public as to which cancers in what group of people are appropriate for screening. These guidelines are similar to the World Health Organization and majority of the developed world’s recommendations.

For the average risk person without symptoms (i.e. those without symptoms or family history of the cancer being screened for), the following cancer screening is recommended for early detection:

Colorectal Cancer

For those age 50 and above,

• Faecal occult blood testing once a year or

• Colonoscopy once every 10 years or

• CT colonography once every 5 years

Cervical Cancer

Cervical cancer is rare among females who have never been sexually active and routine screening in this group is not recommended.

In those who have ever been sexually active, the following is appropriate:

From age 25-29: Pap smear every 3 years

From age 30 and above: HPV DNA test every 5 years

The method of collection between Pap smear and HPV DNA test is the same (the difference is only in the way the test is performed in the laboratory).

Breast Cancer

The standard for breast cancer screening is mammography. However, no test is perfect and there are potential downsides as well as benefits to breast cancer screening. Speak to healthcare professionals about the pros and cons of mammography screening and if appropriate, the following is recommended:

From age 40-49: Mammography screening once a year

From age 50-69: Mammography screening once every 2 years

Cancer screening for other Types of tumours

The above recommendations only apply to those with average risks and no symptoms. If there are additional risk factors such as family history, it may be appropriate to undergo additional tests. However, for a person with average cancer risk in Singapore, having additional screening beyond the guidelines listed above is not appropriate or recommended.

Cancer treatments

The National Cancer Centre Singapore administers chemotherapy, radiation therapy and/or recommends surgery depending on which is the most effective cancer treatment for the patient.

Significant advances have been made in cancer management, and immunotherapy is now on the WHO Essential Medicines List. Only a minority of innovative therapies, however, have a clinically significant impact. Access, sustainability and system readiness must be evaluated before introducing new therapies.