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Understanding Cancer

Cancer develops when cells begin to grow and spread uncontrollably throughout the body, as is often referred to as a malignant tumour. After invading surrounding tissues, cancerous tumours spread to different parts of the body and other organs with almost every part of the body as susceptible to cancer. According to the latest cancer statistics in Hong Kong, colorectal cancer has already surpassed lung cancer as the most common type of cancer, accounting for 17.3% of all cancer cases, pushing breast cancer back to the third most common cancer. In 2016, 31,468 new cancer cases had been recorded in Hong Kong, representing an increase of 3.8% and 1,150 cases from 2015[1].


As cancer has become increasingly prevalent, great strides have been made in cancer treatment, thanks to the advances in medical technology. Early detection of cancerous tumours now enables more timely treatment through medical surgery, radiotherapy or chemotherapy that destroys cancer cells and facilitates full recovery. Taking lung cancer as an example, early-stage lung cancer, with appropriate treatment, can now achieve a survival rate of around 90%[2]. For patients diagnosed with late-stage cancers, the increase in innovative treatments such as targeted therapy and immunotherapy have proven to effectively prolong their lives.

Cancer Grading and Staging System [3]

Before cancer treatment begins, doctors will classify the tumour into one of five stages of cancer from Stage 0 to Stage IV, based on the extent to which cancer has developed and spread. However, there are those cases where staging is not possible. In Hong Kong, cancer staging primarily refers to the TNM staging system established by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC). T describes the size of the tumour; N describes the spread of cancer to nearby lymph nodes; M describes metastasis (spread of cancer to other parts of the body).

Stage 0

Abnormal cells have been detected with the potential to become cancer and spread to surrounding normal-functioning tissues[4].

Stage I

Early-stage cancer has developed, where cancerous cells or tumour have been detected but they remain localised and have not spread to different parts of the body such as the lymph nodes.

Stage II

The primary tumour has advanced and grown larger into the nearby tissues, and has possibly spread into the lymph nodes, but not as yet to other parts of the body.

Stage III

The primary tumour has advanced and grown into the surrounding tissues and has spread into the lymph nodes and beyond to other parts of the body.

Stage IV

Late-stage cancer has been identified, with the tumour having metastasised and spread to the furthest reaches of the body.

Types of Cancer

Cancer can spread to almost all organs and parts of the body. Treatment combinations and options pivot on the extent to which a cancer has developed, which is determined by a range of factors, from the location of cancer, to the cancer stage, to the nature of cancer. Complemented by advanced medical technologies such as genetic testing that can improve clinical outcomes, the emergence of personalised cancer treatments has brought new hope to cancer patients.


Many cancers are difficult to detect in the early stages. If you have noticed abnormal changes in your body such as sudden weight loss, loss of appetite and unusual fatigue for an extended period, you should see your doctor immediately for a thorough check-up. Leading healthier lifestyles will help reduce the risk of cancer, which includes refraining from tobacco and alcohol use.

Click on the types of cancer below for more information.

Colorectal Cancer

Breast Cancer

Liver Cancer

Cervical Cancer

Lung Cancer

Prostate Cancer

Stomach/Gastric Cancer

Pancreatic Cancer

Ovarian Cancer

Nasopharyngeal Carcinoma


1. http://www3.ha.org.hk/cancereg/pdf/overview/Summary%20of%20CanStat%202016.pdf
2. American Cancer Society 2017
3. http://www3.ha.org.hk/cancereg/tc/glossary.html
4. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/carcinoma-in-situ