What is Cancer? Cancer Causes
Unlike most other diseases cancer is not infectious and hence not communicable. Actual cause of cancer could not be identified despite serious effort by researchers. No organism has been found to be associated with the disease till to-day. Cancer is referred to as an ailment characterized by an unrestrained growth of abnormal cells which if untreated and unchecked eventually kills the patient. However, cancer is curable if detected and treated promptly.
Cancer constitutes the leading cause of mortality in India. About four lakhs of people are affected by cancer in India every year of which more than two lakhs people die. Lack of understanding about the disease is the main cause of late detection. Not enough people know about the early symptoms of the disease. People generally report only at the advanced stage of the disease. Lack of adequate detection centres and lack of proper treatment facilities in many states create problems for the patients.
Multicellular organisms grow due to addition of newer and newer cells. The new cells are created from the existing cells through mitotic cell division. This is an orderly process, controlled by the body functions. Sometime due to unknown reason some cells in some organs do not obey the general command and start dividing in abnormally fast rate causing formation of lump or ulceration. The affected area increases rapidly. The formation of lump causes obstruction in the alimentary canal, respiratory tract, urinary bladder which then lead to other serious complications causing disintegration of the system. The abnormal cells cause rapid and total degeneration of the affected organs. The cell degeneration is not restricted to a particular organ but spread rapidly to other organs through tissue fluid. The affected person continuously loses weight due to ever increasing demand of nutrition by the newly formed cancer cells.
Types of Cancer:
(1) Sarcoma: Cancer of muscle, bones, tendons, cartilage, fat, blood vessels, connective tissues are called sarcoma.
(2) Carcinoma: Cancer originating from surface cells of skin or cells which lines the internal organs is called carcinoma.
(3) Lymphoma: Cancer of lymph glands and lymph nodes is called lymphoma.
(4) Leukaemia: Cancer of blood forming organs principally bone marrow. No organ is immune to cancer and no species is free from cancer.
Causes of Cancer
Causes of cancer are not definitely known at present. It is expected that in near future actual causes ill be known. At present the following causes are thought to be associated with the incidence of cancer.
1. A high rate of lungs cancer has been found to be associated with excessive cigarette smoking. Excessive smoking is also believed to be implicated in cancer of the bladder, mouth, throat and larynx.
2. Chewing of tobacco, betel nut etc. is also believed to be the cause of cancer in mouth, throat, pharynx etc.
3. Certain dyes, chemicals, heavy metals, over exposure to X-rays or other kinds irradiation may cause cancer.
4. Alcoholism has been implicated in cancer of liver and gall-bladder.
5. Smoke, dust and chemical pollution may be responsible for cancer of industrial workers.
How all these substances and environmental factors induce cancer is not definitely known, but it is suspected that these substances may affect the genes and cause their mutation. The mutant genes cannot control the normal cell functions. There may be yet another reason for which genetical control of the cell function is adversely affected. It is suspected that sometime the genes of some cells are replaced by some viruses. The viruses in turn bring abnormal changes in cell function causing cancer or Causes of Cancer.
Sites of Cancer in body
Cancer can develop in any organ of the body, but it occurs frequently in some organs such as liver, lungs, alimentary canal, larynx, pharynx, tongue, lips, gall bladder, breast, uterus, urinary tract, lymph nodes, bones etc.
Primary Signs of Cancer
The following signs are also associated with many other diseases and therefore appearance of those signs should not be taken as signs of cancer unless these signs do not subside for a considerable period. If these persist after treatment of suspected ordinary disease then only one should approach an expert for detection of cancer if there is any.
Primary sings are :
1. Unusual bleeding or discharge.
2. A lump or thickening in the breast.
3. A sore that does not heal.
4. Change in bowel and urine habits.
5. Hoarseness and frequent cough.
6. Frequent indigestion.
7. Difficulty in swallowing.
8. Change in colour or position of mole.
9. Any outgrowth in the body.
10. Any wound that does not heal.
How Cancer Spread in the Body
Cancer spread through the following ways : 1. Cancer cell grow through the wall of the blood vessels. 2. Cancer cells are carried by the blood stream to other parts of the body. 3. The cancer cells enter the lymphatic stream and are carried to lymph glands. 4. They spread from one tissue to another tissue.
How Cancer Cells Behave
Normal cells have control machanism to direct when to divide and when not. The control is vested with DNA. It directs action according to necessity. In case of cancerous cells such control is lacking probably because of mutation of some genes. The mutant genes may fail to control normal cell function and hence controlled cell division may be replaced by uncontrolled cell division. It is believed that all cells carry certain cancer causing genes called oncogenes. Generally oncogenes remain inactive. Certain conditions trigger these genes to multiply which then take control of the cells replacing the normal functions.
Suspected involvement of viruses
It is now strongly suspected that some retroviruses that cause tumor may be involved in cancer. These viruses have RNA as genetic material. This kind of RNA has the capacity to integrate with the host DNA. With the help of ‘reverse transcriptase’ such RNA makes a copy of the double stranded DNA which then behave as viral oncogene. The viral oncogenes may interact with the oncogenes of the cell called proto-oncogene to take control of the cell function. The DNA which has been transcribed from viral RNA transcribe back the viral RNA through normal transcription process giving rise to more retroviruses.
Treatment of Cancer
If the cancer is detected in its early stages then it can be cured and the patient can ,live for many years without recurrence of the disease. Cancer can be treated in three different methods or the three methods can be combined.
(1) Surgery helps remove the affected organ or the site of occurrence.
(2) Radiotherapy helps in burning the affected site so that the cancer cannot spread further,
(3) Chemotherapy helps in isolating the affected site and thereby kills the cancer cells.