Malignant And Immune Disease

There are many different types of cancer. Some are more deadly than others. Cancer can originate in any tissue or organ of the body. Although medical science cannot identify a single "cause" of cancer, it is known that many noxious outside influences, collectively known as "carcinogens," can provoke the formation of abnormal cells. Tobacco smoke is such a factor in lung cancer. Long-term overexposure to sunlight induces skin cancer. Some forms of cancer are provoked by the malfunctioning of certain genes inherited from parents. In old age, cancer is a common disease.

Failure of the immune system can lead to increased susceptibility to infections and the development of some kinds of cancer. Such failure can result from infection by human immunodeficiency virus (HIV), the virus that causes AIDS. The functions of the immune system may be deliberately decreased in order to treat certain disorders, while in other instances decreased immune system function may occur as an unfortunate side effect or consequence of a necessary medicament treatment.

In some cases, the immune system can trigger an inappropriate attack on the body's own tissues, leading to what are known collectively as autoimmune disorders. Some common disorders of this type are rheumatoid arthritis, inflammatory skin conditions (lupus erythematosus), inflammation of blood vessels, and some forms of hypothyroidism. The immune system is responsible for the rejection of organ transplants (kidney, heart, liver, etc.), and because of this may have to be partially "turned off" by special medications.

Anticancer medicaments

The body's cells normally grow and divide in an organized way; cells that are old or damaged are regularly replaced by new, healthy cells. Sometimes, however, a single cell becomes free from the controls that regulate cell division, and it multiplies at an unchecked rate. Such excessive growth usually leads to the production of a tumor, which may be either benign or malignant (cancerous).

A benign tumor grows slowly and is restricted to a particular area; it produces harmful effects only when it causes pressure on surrounding tissues. A malignant tumor tends to spread to other parts of the body; this occurs when the original tumor invades neighboring tissues or when cells break off and are carried to other parts of the body, where they start to grow. The secondary growths that result are known as metastases. Cancerous cells are frequently unable to perform their usual functions, and this leads to progressively impaired function of the organ or area concerned.

There are many different factors that can provoke cancerous changes in cells. A combination of factors may be involved, notably an individual's genetic background, immune system failure, and over-exposure to cancer-causing substances (carcinogens). Known carcinogens include strong sunlight (for those who are fair-skinned), viruses, dietary factors, certain chemicals, radiation, and tobacco smoke.

Treating cancer is a complicated process that depends on the type of cancer, its stage of development, and the patient's condition and wishes. Any of the following treatments may be used on its own or in combination: surgical removal of the cancer, radiation treatment, and chemotherapy (that is, the use of anti-cancer medicaments).

Anticancer medicaments that kill cancer cells are sometimes referred to as cytotoxic medicaments. They fall into several classes, according to their chemical composition and principal mode of action: alkylating agents, antimetabolites, and cytotoxic antibiotics are among the most widely used classes. In addition to these medicaments, sex hormones and related substances are also used to treat some types of cancer.

All cytotoxic anticancer medicaments kill cancer cells by preventing them from growing or dividing. Cells grow and divide in several stages. Most anticancer medicaments act on one specific stage. During treatment, several medicaments may be given in sequence in order to eliminate abnormal cells at all stages of development.

Hormone treatments work by opposing the effects of the hormone that encourages the growth of the cancer. For example, some breast cancers are stimulated by the female sex hormone estrogen. Spread of the cancer may thus be limited by a medicament, such as tamoxifen that opposes the effects of estrogen. Other hormone-sensitive cancers are damaged by high doses of a particular sex hormone. Medroxyprogesterone, a progesterone, often halts the spread of endometrial cancer.

At the start of treatment adverse effects of cytotoxic anticancer medicaments are likely to be more noticeable than benefits. The most common side effect is nausea and vomiting, for which an anti-emetic medicament may be prescribed. Diarrhea is also a common side effect. Many anticancer medicaments cause hair loss because of the effect of their activity on the cells of the hair follicles, but the hair usually starts to regrow after chemotherapy has been completed. Individual medicaments may produce other side effects which physicians monitor.

Anticancer medicaments are usually administered in the highest doses that can be tolerated in order to kill as many cancer cells as quickly as possible, and therefore to reduce the risk of the cancer spreading to other parts of the body and forming metastases.

Beneficial effects on the underlying disease may not be apparent for several weeks. The unpleasant side effects of intensive cancer chemotherapy, combined with the lack of immediate response to the treatment, often lead to depression among those receiving anticancer medicaments. Specialist counseling may be helpful.

All cytotoxic anticancer medicaments interfere with the activity of non-cancerous cells and for this reason they often produce serious adverse effects during long-term treatment. In particular, these medicaments often adversely affect the blood-producing cells in the bone marrow. The number of both red and white cells and the number of platelets (particles in the blood which are responsible for clotting) may all be reduced. In some cases, symptoms of anemia (weakness and fatigue) and an increased risk of abnormal or excessive bleeding may develop as a result of treatment. In addition, wounds may take longer to heal, and susceptible people can develop gout as a result of increased release of uric acid (a by-product of cell destruction). Reduction in the number of white blood cells may result in an increased susceptibility to infection.

Because of these problems, anticancer chemotherapy is often given in a hospital, where the effects can be closely monitored. Several short courses of medicament treatment are often given, thus allowing the bone marrow time to recover in the intervening period. Blood tests are performed regularly. Where necessary, blood transfusions, antibiotics, or other forms of treatment are used to overcome the adverse effects. Where relevant, contraceptive advice is given early in treatment, because most anticancer medicaments can damage a developing baby.

Immunosuppressant medicaments

The body is protected against attack from bacteria and viruses by the specialized cells and proteins in the blood and tissues that make up the immune system. White blood cells known as lymphocytes either kill these invading organisms directly or produce special proteins (antibodies) to destroy them. These mechanisms are also responsible for eliminating abnormal or unhealthy cells that could otherwise multiply and develop into a cancer.

In certain conditions, it is medically necessary to dampen the activity of the immune system. These include a number of autoimmune disorders in which the immune system attacks normal body tissue. Autoimmune disorders may affect a single organ -for example, the kidneys in Goodpasture's syndrome or the thyroid gland in Hashimoto's disease -or may cause widespread damage, as in rheumatoid arthritis or systemic lupus erythematosus.

Immune system activity may also need to be reduced following an organ transplant, when the body's defenses would otherwise attack and reject the transplanted tissue.

Several types of medicaments are used as immunosuppressants: anticancer medicaments, corticosteroids, and cyclosporine. Immunosuppressant medicaments reduce the effectiveness of the immune system either by depressing the production of lymphocytes or by altering their activity.

When immunosuppressants are given to treat an autoimmune disorder they reduce the severity of the symptoms and in many cases temporarily halt the progress of the disease. However, they cannot restore major tissue damage, such as damage to the joints in rheumatoid arthritis.

Corticosteroids often promote a general feeling of well-being, but given in doses high enough to produce an immunosuppressant effect, they may also produce unwanted effects. Anticancer medicaments, when prescribed as immunosuppressants, are given in low doses that produce only mild side effects. They may cause nausea and vomiting, for which an anti-emetic medicament may be prescribed. Hair loss may occur, but hair growth usually resumes when the medicament is discontinued. Cyclosporine may cause increased growth of facial hair, swelling of the gums, and tingling in the hands.

All of these medicaments may produce potentially serious adverse effects. By reducing immune system activity, immunosuppressant medicaments can affect the body's ability to fight invading microorganisms, thereby increasing the risk of serious infections. Because lymphocyte activity is also important for preventing the multiplication of abnormal cells, there is an increased risk of certain types of cancer. A major drawback of anticancer medicaments is that, in addition to their effect on the production of lymphocytes, they interfere with the growth and division of other blood cells in the bone marrow. Reduced production of red blood cells can cause anemia; when the production of blood platelets is suppressed, blood clotting may be less efficient.

Because cyclosporine is more specific in its action than corticosteroids or anticancer medicaments, it produces fewer troublesome side effects. However, it may cause kidney damage, and in too high a dose may affect the brain, causing hallucinations or seizures. Cyclosporine also tends to raise blood pressure, and another medicament may be required to counteract this effect. Immune deficiency occurs when the body's immune system, which normally protects the body against infecting organisms and the development of cancer, fails.

Medicaments for aids and immune deficiency

Immune deficiency may be present from birth because the body's immune system has not developed normally, or it may occur during medicament treatment (for example, with corticosteroids or anticancer medicaments), or as a result of cancer or infection.

AIDS (acquired immune deficiency syndrome) is a disorder caused by infection with HIV (human immuno-deficiency virus). The virus invades certain types of cells, particularly the white blood cells known as T-helper lymphocytes. T-helper lymphocytes normally activate other cells in the immune system to produce antibodies to fight infection. Because the AIDS virus kills T-helper lymphocytes, the body is unable to fight the AIDS virus or any subsequent infection.

There may be a long interval between infection with the HIV virus and the development of AIDS. Not everybody who is HIV positive progresses to AIDS. Illnesses that commonly affect people with AIDS include candidiasis (thrush), herpes simplex infections, tuberculosis, cryptococcal meningitis, lymphomas, Kaposi's sarcoma (a rare form of skin cancer), pneumocystis carinii pneumonia (PCP), and dementia.

Serious infections are the most common consequence of all immune-deficiency disorders. These are treated with a variety of antibiotics, antiviral medicaments, and antifungal medicaments. The antiprotozoal medicament pentamidine may be used to treat PCP.

Kaposi's sarcoma and other cancers are not consistently treated with anticancer medicaments, since there is an added risk of depressing the immune system. Radiation therapy may be given instead.

When serious AIDS-related infections have occurred, the antiviral medicaments zidovudine (AZT), didanosine, or zalcitabine may be prescribed. They do not provide a cure but may prolong life expectancy. HIV patients may be given treatment to prevent some of these conditions, especially PCP and tuberculosis.

Comments