What is cancer?
Cancer is a disease, with which cells divide and grow uncontrollably, potentially spread and affect different parts of body.

How is cancer formed & spread?
Cancer can occur in any part of our body. Normally cell division in our body is closely controlled; however when a number of genetically mutated cells divide uncontrollably, they form a mass called tumor. Dislodge from tumor, cancer cells can enter blood circulation and lymphatic system, metastasizing to other organs or tissues.

Tumors may be benign or malignant. Benign tumors are localized, with a slow paste of growth without tendency of invading other tissues and organs; in the contrary malignant tumors possess ability of growing fast and the potential of invading other parts of the body via metastasis.



What are the causes of cancer?
Further investigation needs to be done to understand the risks and causes of cancer fully. On top of heredity factors, strong evidences of causing cancer have been observed in some physical, chemical or biological agents, which are referred to as carcinogens. According to International Agency for Research on Cancer (IARC) under World Health Organization (WHO), the classification of carcinogens is as follows:

AGENTS CLASSIFIED BY THE IARC MONOGRAPHS,
Group Definition
1 Carcinogenic to humans
2A Probably carcinogenic to humans
2B Possibly carcinogenic to humans
3 Not classifiable as to its carcinogenicity to humans

Group 1 Carcinogens
1.Tobacco smoking (including second-hand smoking)
2. Alcoholic beverages
3. Aflatoxin
4. Helicobacter pylori
5. Hepatitis B virus
6. Hepatitis C virus
7. Human Immunodeficiency Virus
8. Human Papillomavirus types 16, 18, 31,33,35,39 etc.
9. Epstein-Barr Virus
10. Ultraviolet radiation
11. Benzene,
12. Salted fish (Chinese style)
13. Radon
14. Some metals like Cadmium, Radium, Beryllium
15. Soot
16. Mineral oil (Untreated or mildly treated)
17. Oral contraceptives, combined estrogen-progestogen
18. Some drugs like Tamoxifen
19. Areca palm seed
20. Wood dust
21. Asbestos
22. Occupation exposure to rubber manufacturing
23. Ingestion of processed meat
24. Diesel exhaust
25. Polychlorinated biphenyl
26. Welding fume
27.Occupation exposure to aluminum/iron/steel manufacture
28. Occupation exposure to coke production
29. All forms of ionizing radiation

Group 2A & 2B Carcinogens:
1. Ingestion of red meat (2A)
2. Malaria (2A)
3. Night shift work (2A)
4. Drinking beverage >65oC (2A)
5. Emissions from high-temperature oil frying
6. DDT pesticide
7. Human Papillomavirus type 68 (2A)
8. Occupation exposure as hairdresser (2A)
9. Petroleum refining (2A)
10. Gasoline exhaust (2B)
11. Gasoline (2B)
12. Surgical implants (2B)
13. Pickled vegetable (2B)
14. Coconut oil diethanolamine condensate (2B)
15. Perineal use of Talc-based body powder (2B)
16. Lead (2B)
17. Caffeic acid (2B)
18. Occupation exposure to textile industry (2B)
19. Occupation exposure to printing processes (2B)

For more details, please refer to the website of IARC:
http://monographs.iarc.fr/ENG/Classification/


How significant is cancer in Hong Kong?
Cancer is a top killer in Hong Kong. According to the Hong Kong Cancer Registry, there were approximately 34,000 cancer incidence and approximately 14,000 cancer mortality recorded in 2018 alone. The median age of incidence for male is 68, whereas 62 for female. It is projected from statistics of the Government, that cancer incidence will reach 42,000 per annum before 2030.

Which cancer types are the most common in Hong Kong?
Top ten cancers in terms of incidence are as follows:
1. Colorectal Cancer
2. Lung Cancer
3. Breast Cancer
4. Prostate Cancer
5. Liver Cancer
6. Stomach Cancer
7. Corpus uteri Cancer
8. Non-Melanoma Skin Cancer
9. Thyroid Cancer
10. Non-Hodgkin Lymphoma


Top five common cancers in men:
1. Colorectal Cancer
2. Lung Cancer
3. Prostate Cancer
4. Liver Cancer
5. Stomach Cancer


Top five common cancers in female:
1. Breast Cancer
2. Colorectal Cancer
3. Lung Cancer
4. Corpus uteri Cancer
5. Thyroid Cancer


Which cancer types are the most deadly in Hong Kong?
It is worth mentioning that incidence of cancers does not necessarily correlates with mortality of cancers. Lung cancer for instance, was ranked second in cancer incidence, but at the same time lung cancer is the top killer among all types of cancers; liver cancer was ranked fifth in incidence, but third in cancer mortality. Top three cancers by mortality for men and women are as follows:

Men:
1. Lung Cancer
2. Colorectal Cancer
3. Liver Cancer

Women:
1. Lung Cancer
2. Colorectal Cancer
3. Breast Cancer



Last update: 22 Oct 2020


Source:
  • Agents Classified by the IARC Monographs, Volumes 1–127 ... (2020, June 26). Retrieved September 30, 2020, from https://monographs.iarc.fr/agents-classified-by-the-iarc/
  • CP, W., E, W., & BW, S. (2020). World Cancer Report: Cancer Research for Cancer Prevention. Retrieved September 29, 2020, from http://publications.iarc.fr/586
  • Hong Kong Cancer Strategy 2019 - Food and Health Bureau. (2019, July). Retrieved September 29, 2020, from https://www.fhb.gov.hk/download/press_and_publications/otherinfo/190700_hkcs/e_hkcs_fully.pdf
  • Overview of Hong Kong Cancer Statistics of 2017. (2019, October). Retrieved September 29, 2020, from https://www3.ha.org.hk/cancereg/pdf/overview/Summary%20of%20CanStat%202017_tc.pdf