Cancer
- Cancer causes about 4 million deaths annually throughout the world.
- Cancer is an abnormal and uncontrolled division of cells that invade and destroy surrounding tissue forming a tumour or neoplasm (new growth).
- It is a heterogeneous group of cells that do not respond to normal cell division.
- The cancerous cells migrate to distant parts of the body and affect new tissues. This process is called metastasis.
- The frequent sites of metastasis are lungs, bones, liver, skin and brain.
Types of Cancers
- Cancers are classified on the basis of the tissues from which they are formed.
Carcinomas
- Carcinomas arise from epithelial and glandular tissues. They include cancers of the skin, lungs, stomach and brain. About 85% of the tumours are carcinomas
Sarcomas
- Sarcomas occur in the connective and muscular tissue.
- They include the cancer of bones, cartilage, tendons, adipose tissue and muscles.
- These form 1% of all tumours.
Carcinogenic Agents
- Cancer-causing agents are called carcinogens.
- They are physical, chemical agents, ionizing radiations and biological agents.
Physical Irritant:
- Heavy smoking causes lung cancer and cancers of oral cavity, pharynx (throat) and larynx.
- Betel and tobacco chewing causes oral cancer. Excessive exposure to sunlight may cause skin cancer.
Chemical agents:
- Nicotine, caffeine, products of combustion of coal and oil, pesticides, asbestos, nickel, certain dyes and artificial sweetners induce cancer.
Radiations:
- Ionizing radiations like X-rays, gamma-rays, radioactive substances and non-ionising radiations like UV rays cause DNA damage leading to cancer.
Biological agents:
- Cancer causing viruses are called oncogenic viruses.
Treatment of Cancer
- Surgery: Tumours are removed by surgery to prevent further spread of cancer cells.
- Radiation therapy: Tumour cells are irradiated by lethal doses of radiation while protecting the surrounding normal cells.
- Chemotherapy: It involves administration of anticancerous drugs which prevent cell division and are used to kill cancer cells.
- Immunotherapy: Biological response modifiers like interferons are used to activate the immune system and help in destroying the tumors.
Preventive measures for Cancer
- Cancer control programmes should focus on primary prevention and early detection.
- To prevent lung cancer tobacco smoking is to be avoided and protective measures to be taken against exposure to toxic pollutants of industries.
- Excessive exposure to radiation is to be avoided to prevent skin cancer.