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Cancer is a major cause of death all over the world. More than a million Indians suffer from cancer and a large number of them die from it annually. Cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth.
Cancerous cells just continue to divide giving rise to masses of cells called tumors. Tumors are of two types namely benign and malignant. Benign tumors normally remain confined to their original location and do not spread to other parts of the body.
The malignant tumors, cells grow very rapidly, invading and damaging the surrounding normal tissues. These cells reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there.
Causes of cancer:
Transformation of normal cells into cancerous cells may be induced by physical, chemical or biological agents. Ionizing radiations like X-rays and gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation.
The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer. Furthermore, several genes have been identified in normal cells which, when activated under certain conditions, could lead to monogenic transformation of the cells.
Cancer detection and diagnosis:
Early detection of cancers allows the disease to be treated successfully in many cases. Cancer detection is based on biopsy and histopathological studies of the tissue and blood and bone marrow tests for increased cell counts in the case of leukemia’s.
In biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under microscope by a pathologist. Techniques like radiography, CT and MRI are very useful to detect cancers of the internal organs. Antibodies against cancer-specific antigens are also used for detection of certain cancers. Techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers.
Treatment of cancer:
The common approaches for treatment of cancer are surgery, radiation therapy and immunotherapy. In radiotherapy, tumor cells are irradiated lethally, taking proper care of the normal tissues surrounding the tumor mass.
Several chemotherapeutic drugs are used to kill cancerous cells. Some of these are specific for particular tumors. Majority of drugs have side effects like hair loss, anemia, etc. Most cancers are treated by combination of surgery, radiotherapy and chemotherapy.
Cancer is now a general term for more than 100 diseases that are characterized by uncontrolled, abnormal growth of cells. Cancer cells can spread locally or through the bloodstream and lymphatic system to other parts of the body.