| Much of the promise for cancer prevention | | | | Most forms of chemotherapy target all rapidly |
| comes from observational epidemiologic studies | | | | dividing cells and are not specific for cancer cells. |
| that show associations between modifiable life | | | | Hence, chemotherapy has the potential to harm |
| style factors or environmental exposures and | | | | healthy tissue, especially those tissues that have a |
| specific cancers. | | | | high replacement rate (e.g. intestinal lining). These |
| Cancer is a class of diseases or disorders | | | | cells usually repair themselves after |
| characterized by uncontrolled division of cells and | | | | chemotherapy. Treatment of some leukaemias |
| the ability of these to spread, either by direct | | | | and lymphomas requires the use of high-dose |
| growth into adjacent tissue through invasion, or | | | | chemotherapy, and total body irradiation (TBI). |
| by implantation into distant sites by metastasis | | | | This treatment ablates the bone marrow, and |
| (where cancer cells are transported through the | | | | hence the body's ability to recover and repopulate |
| bloodstream or lymphatic system). Cancer may | | | | the blood. |
| affect people at all ages, but risk tends to | | | | Radiation therapy (also called radiotherapy, X-ray |
| increase with age. There are many types of | | | | therapy, or irradiation) is the use of ionizing |
| cancer. Most cancers are named for where they | | | | radiation to kill cancer cells and shrink tumors. |
| start. For example, lung cancer starts in the lung, | | | | Radiation therapy can be administered externally |
| and breast cancer starts in the breast. The | | | | via external beam radiotherapy (EBRT) or |
| spread of cancer from one part of the body to | | | | internally via brachytherapy. The effects of |
| another is called metastasis. Severity of | | | | radiation therapy are localised and confined to the |
| symptoms depends on the site and character of | | | | region being treated. Radiation. Hormone-sensitive |
| the malignancy and whether there is metastasis. | | | | tumors include certain types of breast and |
| Cancer is caused by damage to DNA, resulting in | | | | prostate cancers. Removing or blocking estrogen |
| mutations to genes that encode for proteins | | | | or testosterone is often an important additional |
| controlling cell division. Many mutation events may | | | | treatment. Pain medication, such as morphine and |
| be required to transform a normal cell into a | | | | oxycodone, and antiemetics, drugs to suppress |
| malignant cell. This tissue is obtained by biopsy or | | | | nausea and vomiting, are very commonly used in |
| surgery.. These mutations can be caused by | | | | patients with cancer-related symptoms. Cancers |
| radiation, chemicals or physical agents that cause | | | | can be cured if entirely removed by surgery, but |
| cancer, which are called carcinogens, or by certain | | | | this is not always possible. When the cancer has |
| viruses that can insert their DNA into the human | | | | metastasized to other sites in the body prior to |
| genome. Mutations occur spontaneously, and may | | | | surgery, complete surgical excision is usually |
| be passed down from one cell generation to the | | | | impossible. |
| next as a result of mutations within germ lines. | | | | Prevention of Cancer |
| However, some carcinogens also appear to work | | | | Cancer prevention is defined as active measures |
| through non-mutagenic pathways that affect the | | | | to decrease the incidence of cancer. Use of |
| level of transcription of certain genes without | | | | exogenous hormones, exposure to ionizing |
| causing genetic mutation. | | | | radiation and ultraviolet radiation, certain |
| Treatment of Cancer | | | | occupational and chemical exposures, and |
| Cancer can be treated by surgery, | | | | infectious agents. Alcohol consumption, Smoking |
| chemotherapy, radiation therapy, immunotherapy, | | | | (although 20% of women with lung cancer have |
| monoclonal antibody therapy or other methods. | | | | never smoked, versus 10% of men. Cancer |
| Chemotherapy is the treatment of cancer with | | | | however, compared with tobacco exposure, the |
| drugs ("anticancer drugs") that can destroy cancer | | | | magnitude of effect is modest or small and the |
| cells. It interferes with cell division in various | | | | strength of evidence is often weaker. Do not |
| possible ways, e.g. with the duplication of DNA or | | | | take the Alcohol and No Smoking. |
| the separation of newly formed chromosomes. | | | | |