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Cancer

15
...
18)
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Some of these can be inherited from
parents, some by exposure to certain substances from the environment, and
some may be the result of the cancer itself because as cancer develops, it
damages local tissues and causes inflammation
...
A tumour can be:
• benign – contained within a thick fibrous capsule; it grows slowly and does
not destroy the tissue in which it originates, or spread to other sites
• malignant – tends to grow quickly, spreads to other tissues and organs, and
threatens life or wellbeing (k Table 15
...
19)
...
18 Worldwide, the
most common causes of
death from cancer are lung,
liver, colorectal (bowel),
stomach and breast
...
10
...


Metastasis
Metastasis is the development of secondary malignant growths at a distance
from a primary site of cancer
...
In order to do this, the cells must escape by moving through the
extracellular space and penetrating blood or lymph vessel walls
...


Table 15
...
g
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19 When a primary skin
cancer, e
...
melanoma (k 15
...
5,
item 4) spreads to form a
metastatic tumour in the
skeleton, the secondary tumour
is called metastatic bone cancer,
not bone cancer, because it will
have cellular and molecular
features of the original skin
cancer cells
...
10
...
20 Since the 1970s, dozens
of oncogenes have been
identified in human cancer, and
many chemotherapy drugs target
the proteins encoded by the
oncogenes
...
21 An example of a
tumour suppressor gene is the
p53 gene
...
3
...


Cancer is a complex disease that can arise in almost any part of the body
when an error occurs in gene expression – the way that cells divide, grow
and develop
...
3
...
Mutations
are sometimes known as the ‘drivers’ of cancer and can affect oncogenes,
tumour suppressor genes and DNA repair genes
...
If mutations
arise in these genes, they can become oncogenes
...
When
mutations occur in a cell’s genes, most normal cells undergo apoptosis
...

Most oncogenes require an additional factor before they can cause cancer,
e
...
mutations in another gene, or environmental factors such as a viral
infection or smoking
...
20)
...
21)
...

DNA repair genes are responsible for fixing and repairing DNA that has
become damaged
...


15
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2 Progression of cancer

Box 15
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In healthy tissue, cells mature into very specific types, each of which
performs a specialised function in the tissue and has a predictable
relationship with neighbouring cells, e
...
muscle cells work together to
contract
...
3
...
The rate of replacement is subject
to homeostatic regulations that determine whether new cells are required
and the space available
...
Examples of
abnormal cell behaviour are:
• hyperplasia – cells ignore the signals that normally stop mitosis or trigger
apoptosis (k Box 15
...
15
...


invasive cancer

cell containing a
mutation

in situ cancer
hyperplasia

dysplasia

PRECANCEROUS STAGE

MALIGNANT STAGE

cancer
cells
being
shed

Fig
...
13 Progression from a pre-cancerous stage to increasingly abnormal stages to malignancy
...
10
...
A carcinogen is defined as any substance or agent
that is capable of promoting cancer, but the risk
of developing cancer depends on many different factors, including the individual’s
genetic make-up and the length and intensity of their exposure to:
• tobacco smoke
• alcohol misuse
• low fruit and vegetable diet
• asbestos
• a high body mass index
• urban air pollution
• lack of physical activity
• ionising radiation
• certain bacteria, e
...
Helicobacter pylori
• some viruses, e
...
hepatitis B and C, human papillomavirus, Epstein–
Barr virus
...
10
...

As a tumour grows and swells it causes symptoms that include pain (which is often
feared), weight loss (cachexia) and weakness, often as a result of substances and toxins
released by the tumour cells
...


Taking it Further
Diet appears to play an
important part in the
prevention of cancer
...


Diagnosis of cancer is by histological tests (microscopic examination of
tissue samples) and by detection of ‘biomarkers’ such as the proteins and
hormones made by the cancer cells
...
10
...


1
...
23 More than half of
new cases of cancer in the UK
in 2014 were carcinomas of the
breast, prostate, lung or bowel
...
24 In the UK, lung cancer
is rare in people under 40 but
rises sharply with age, being
most commonly diagnosed in
people aged 70–74
...
5
...
23)
...
24)
• transitional cell carcinomas form in the special type of epithelium that is
found in the lining of the ureters and bladder
...
Sarcoma
Sarcomas can form in the soft connective tissues of the body and include
cancers of muscle, tendons and ligaments, blood and lymph vessels and
adipose tissue
...
Leukaemia
Leukaemia is the name given to cancers that originate in bone marrow
where blood cells are formed (k 2
...
1)
...
A reduction
in numbers of normal white cells means that it becomes harder to control
bleeding, fight infections and deliver oxygen to body organs and systems
...
Lymphatic system cancers
• Lymphoma begins in T or B lymphocytes and abnormal ones build up in
lymph vessels and nodes as well as other tissues
...
Although
they most usually form in skin, melanomas can also form in other areas of
pigmentation, e
...
choroid of the eye
...
5
...


5
...
5
...
They can be further identified according to the type of glial
cell in which the tumour starts, e
...
astrocytic cell tumours start in the
astrocytes
...


15
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6 Treatment for cancer
A significant proportion of primary cancers can be successfully treated by
surgery, radiotherapy or chemotherapy, and many cancers have a good chance
of being cured if they are detected and treated early
...
70%
of all cancer deaths happen in low- or middle-income countries where access
to adequate cancer care may be problematic (k Box 15
...


Cell cycle and cancer treatment
For health professionals, understanding of the cell cycle (k Fig
...
4) is
important in cancer treatment because some therapies work best when cells
are actively dividing, e
...
:
• radiation therapy seems to be most effective when cells are undergoing cell
division in the M phase
• some chemotherapy drugs work by attacking cells in a particular phase of
the cell cycle such as G1, S or G2 phase (k 13
...
1)
• checkpoint inhibitors – a form of immunotherapy that activate anti-tumour
immunity thus enabling T cells to seek out and attack the cancer cells
...
Disease refers to any condition that impairs normal function of one or
more organs of the body
...
Epidemics occur when disease spreads rapidly through a population,
becoming pandemic if the disease crosses international boundaries
...
Pathogens are microorganisms that cause infectious disease – bacteria,
viruses, fungi, parasites and prions
...
The chain of infection refers to the way pathogens are transmitted from
one person to another; thus infection control is about disrupting the
chain to reduce the spread of infectious (communicable) disease
...
Cancer refers to a collection of non-communicable diseases that can arise
in almost any part of the body when errors occur in gene expression
...
25 Cancer is the fastest
growing disease worldwide
with an estimated 12 million
people diagnosed with cancer
each year

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