McKenna's Pharmacology for Nursing, 2e

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P A R T 2  Chemotherapeutic agents

Primary tumour

cancers diagnosed, 67,260 were diagnosed in males and 53,460 in females. The estimated five most commonly diagnosed cancers in 2012 were prostate (18,560), bowel (15,840), breast (14,680), melanoma of the skin (12,510) and lung (11,280). Cancer control is one of the Australian government’s nine National Health Priority Areas. For more information on cancer-associated indi­ cators and risk factors, see www.aihw.gov.au/cancer/ cancer-in-australia. Types of cancer Cancers can be divided into two groups: (1) solid tumours; and (2) haematological malignancies such as the leukaemias and lymphomas, which occur in the blood-forming organs. Solid tumours may originate in any body organ and may be further divided into carci­ nomas , or tumours that originate in epithelial cells, and sarcomas , or tumours that originate in the mesen­ chyme and are made up of embryonic connective tissue cells. Examples of carcinomas include granular cell tumours of the breast, bronchogenic tumours arising in cells that line the bronchial tubes and squamous and basal tumours of the skin. Sarcomas include osteo­ genic tumours, which form in the primitive cells of the bone, and rhabdomyosarcomas, which occur in striated muscles. Haematological malignancies involve the blood-forming organs of the body, the bone marrow and the lymphatic system. These malignancies alter the body’s ability to produce and regulate the cells found in the blood. ■■ Cancers arise from a single abnormal cell that multiplies and grows. ■■ Cancer cells lose their normal function (anaplasia), develop characteristics that allow them to grow in an uninhibited way (autonomy) and have the ability to travel to other sites in the body that are conducive to their growth (metastasis). They also have the ability to grow new blood vessels to feed the tumour (angiogenesis). ■■ The goal of cancer chemotherapy is to decrease the size of the neoplasm so that the human immune system can deal with it. ANTINEOPLASTIC DRUGS Antineoplastic drugs can work by affecting cell survival or by boosting the immune system in its efforts to combat the abnormal cells (see Figure 14.3). Chapter 17 discusses the immune agents that are used to combat cancer. This chapter focuses on those drugs that affect cell survival. The antineoplastic drugs that are commonly KEY POINTS

Grows and invades surrounding tissue

Moves into basement membrane of capillaries surrounding the tumour

Enters the bloodstream

Leaves the bloodstream through capillary walls

Proliferates at this new site, grows and invades surrounding tissue

FIGURE 14.2  Metastasis of cancer cells.

abnormal cells and destroy them; antibodies, which form in response to parts of the abnormal cell protein; interferons; and tissue necrosis factor (TNF) all play a role in the body’s attempt to eliminate the abnormal cells before they become uncontrollable and threaten the life of the host. Once the neoplasm has grown and enlarged, it may overwhelm the immune system, which is no longer able to manage the problem. Causes of cancer What causes the cells to mutate and become genetically different is not clearly understood. In some cases, a genetic predisposition to such a mutation can be found. Breast cancer, for example, seems to have a definite genetic link. In other cases, viral infection, constant irritation and cell turnover and even stress have been blamed for the ensuing cancer. Stress reactions suppress the activities of the immune system (see Chapter 29), so if a cell is mutating while a person is under prolonged stress, research suggests that the cell has a better chance of growing into a neoplasm than when the person’s immune system is fully active. Pipe smokers are at increased risk for development of tongue and mouth cancers because the heat of the pipe and chemicals in the pipe tobaccos and smoke continuously destroy normal cells, which must be replaced rapidly, increasing the chances for development of a mutant cell. People living in areas with carcinogenic or cancer-causing chemicals in the air, water or even the ground are at increased risk of developing mutant cells in response to exposure to these toxic chemicals. Cancer clusters are often identi­ fied in such high-risk areas. Not everyone exposed to carcinogens or undergoing stress or having a genetic pre­ disposition to develop cancer actually develops cancer. Researchers have not discovered what the actual trigger for cancer development is or what protective abilities some people have that other people lack. Most likely, a mosaic of factors coming together in one person leads to development of the neoplasm. The estimated total number of new cancers diag­ nosed in Australia in 2012 was 120,710. Of these new