Cancer is a disease in which the cells in part of a person’s body grow uncontrollably. Although there a many different types of cancer, they all develop as a result of uncontrolled growth of abnormal malignant cells.

Normally, cells grow, divide and die in an orderly way. The rates of new cell growth and old cell death are kept in balance. In a healthy person, the cells divide at a rate to repair injuries and to replace depleted or dying cells, while the old and damaged cells self-destruct in a process known as apoptosis.

This normal balance is disrupted during the development of cancer. Cancer cells continue to grow and divide uncontrollably, outliving normal cells and continuing to form new abnormal cells. This increase in cell division generates a growing mass of tissue known as a tumor or neoplasm. As new cells are being produced in greater numbers than needed by the body, the tumor will increase in size. The growth rate of a tumor depends on the rate of cell division. When cells divide rapidly, the tumor will grow quickly and vice versa.

Typically, cancer forms as a tumor. However, not all tumors are malignant. Noncancerous or benign tumors do not spread and are normally not life threatening. Some types of cancer do not involve tumor masses in one place, but are diffused throughout the body. An example is the leukemias, which involve the blood and blood-forming organs.

Frequently, cancer cells travel from the initial tumor to other areas of the body where they begin to grow and replace healthy tissue. There are two main terms used to describe the spread of cancer from its original location:

Invasion. Cancer cells invade neighboring tissues. For example, invasive cancer cells in the breast may penetrate into tissues within or near the breast.
Metastasis. Cancer spreads beyond the immediate neighboring area to other body areas. It may penetrate the lymph vessels and blood vessels, enter the bloodstream and invade normal tissue in adjacent and distant areas of the body. The likelihood that cancer will metastasize depends on the type of cancer and its stage. Although each patient’s case is unique, some types of cancer have a tendency to spread to certain areas, including the lungs, bones and brain.

Cancer can develop almost anywhere in the body. Although it may spread to other parts of the body, it is always named for the area where it originated. For example, melanoma (cancer of the cells that produce skin coloring) that spreads to the liver is classified as metastatic melanoma, not liver cancer

Surgery:
Surgery can be used to prevent, treat, stage, and diagnose cancer. In relation to cancer treatment, surgery is done to remove tumors or as much of the cancerous tissue as possible. It is often performed in conjunction with chemotherapy or radiation therapy.
For those whose cancer is not treatable, palliative surgery may be an option to relieve pain that may be caused by the cancer. Palliative surgery is not intended to treat cure the cancer, or even to prolong life, but to lessen discomfort.

Chemotherapy:
Chemotherapy involves the use of drugs to elimate cancer cells. Unlike surgery, chemotherapy is a type of treatment that affects the entire bosy, not just a specific part. it works by targeting rapidly multiplying cancer cells. Unfortunately, other types of cells in our bodies multiply at high rates, like hair follicle cells and the cells that line our stomachs. This is the cause for side effects like hair loss and stomach upset.

Chemotherapy is most commonly given by pill or intraveiniously (IV), but can be given in other ways. A single type of chemotherapy or drug or a combination of drugs may be prescribed for a sepcific length of time. Like surgery, chemotherapy can be prescribed alone, in conjunction with radiation therapy or biologic therapy.

Radiation Therapy:
Radiation therapy uses certain types of energy to shrink tumors or eliminate cancer cells. It works by damaging a cancer cell's DNA, making it unable to multiply. Cancer cells are highly sensitive to radiation and typically die when treated. Nearby healthy cells can be damaged as well, but are resilient and are able to fully recover.

Radiation therapy may be given alone, along with chemotherapy, and/or with surgery. The decision to combine radiation therapy with other types of treatment depends on the stage of cancer and other factors.

Immunotherapy:
Immunotherapy is treatment that uses the body's own immune system to fight cancer. The immune system is stimulated by an outside source, such as an antibody, or synthetic immune system proteins. Immunotherapy is used in select types of cancer and is not available for everyone. Immunotherapy is given in conjunction with other cancer treatments.

Tobacco the chief culprit
Tobacco is the single largest preventable cause of cancer in the world today. It causes 80-90% of all lung cancer deaths, and about 30% of all cancer deaths in developing countries, including deaths from cancer of the oral cavity, larynx, oesophagus and stomach.

Dietary Factors
Dietary modification is another important approach to cancer control. There is a link between overweight and obesity to many types of cancer such as oesophagus, colorectum, breast, endometrium and kidney. Diets high in fruits and vegetables may have a protective effect against many cancers. Conversely, excess consumption of red and preserved meat may be associated with an increased risk of colorectal cancer

Role of Exercise
Regular physical activity and the maintenance of a healthy body weight, along with a healthy diet, will considerably reduce cancer risk.

Infections as a risk for Cancers
Infectious agents are responsible for almost 22% of cancer deaths in the developing world and 6% in industrialized countries. Viral hepatitis B and C cause cancer of the liver; human papilloma virus infection causes cervical cancer; the bacterium Helicobacter pylori increases the risk of stomach cancer. In some countries the parasitic infection schistosomiasis increases the risk of bladder cancer and in other countries the liver fluke increases the risk of cholangiocarcinoma of the bile ducts. Preventive measures include vaccination and prevention of infection and infestation

Radiation Exposure
Exposure to ionizing radiation is also known to cause to certain cancers. Excessive solar ultraviolet radiation increases the risk of all types of cancer of the skin. Avoiding excessive exposure, use of sunscreen and protective clothing are effective preventive measures.

Occupational Exposure

Asbestos can cause lung cancer; aniline dyes have been linked to bladder cancer; and benzene can lead to leukaemia. The prevention of certain occupational and environmental exposure to these and other chemicals is another important element in preventing cancer