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P A R T 2
Chemotherapeutic agents
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
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
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
Primary tumour
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.
