CANCER DISEASE
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Cancer is a class of diseases characterized by out-of-
control cell growth. There are over 100 different types of
cancer, and each is classified by the type of cell that is
initially affected.
Cancer harms the body when altered cells divide
uncontrollably to form lumps or masses of tissue called
tumors (except in the case of leukemia where cancer
prohibits normal blood function by abnormal cell division
in the blood stream). Tumors can grow and interfere
with the digestive, nervous, and circulatory systems, and
they can release hormones that alter body function.
Tumors that stay in one spot and demonstrate limited
growth are generally considered to be benign.
More dangerous, or malignant, tumors form when two
things occur:
a cancerous cell manages to move throughout the body
using the blood or lymphatic systems, destroying
healthy tissue in a process called invasion
that cell manages to divide and grow, making new blood
vessels to feed itself in a process called angiogenesis.
When a tumor successfully spreads to other parts of the
body and grows, invading and destroying other healthy
tissues, it is said to have metastasized. This process
itself is called metastasis, and the result is a serious
condition that is very difficult to treat.
According to the American Cancer Society, Cancer is the
second most common cause of death in the US and
accounts for nearly 1 of every 4 deaths. The World
Health Organisation estimates that, worldwide, there
were 4 million new cancer cases and 8.2 million cancer-
related deaths in 2012 (their most recent data).
Individual types of cancer
There are said to be over 200 different types of cancer.
We have the following common cancer types covered in
individual Knowledge Center articles:
Anal cancer
Bladder cancer
Bone cancer
Breast cancer
Cervical cancer
Colon cancer
Colorectal cancer
Endometrial cancer
Kidney cancer
Leukemia
Liver cancer
Lymphoma
Ovarian cancer
Pancreatic cancer
P c
S c
T c
T c
V c
V c
Latest cancer research
We are a leading publisher of worldwide cancer news
and research. You can find all our latest news in our
cancer news section.
The rest of this article will focus on what cancer is,
what causes cancer, the symptoms, diagnosis and
available treatments.
Fast facts on cancer
Here are some key points about cancer. More detail and
supporting information is in the main article.
• More than 575,000 people die of cancer, and more
than 1.5 million people are diagnosed with cancer per
year in the US.
• Cancer is considered to be one of the leading causes
of morbidity and mortality worldwide.
• The financial costs of cancer in the US per year are an
estimated $263.8 billion in medical costs and lost
productivity.
• African Americans are more likely to die of cancer than
people of any other race or ethnicity.
• It is believed that cancer risk can be reduced by
avoiding tobacco, limiting alcohol intake, limiting UV ray
exposure from the sun and tanning beds and
maintaining a healthy diet, level of fitness and seeking
regular medical care.
• Screening can locate cervical cancer, colorectal cancer
and breast cancer at an early, treatable stage.
• Vaccines such as the human papillomavirus (HPV)
vaccine assists in preventing some cervical, vaginal,
vulvar, and oral cancers. A vaccine for hepatitis B can
reduce liver cancer risk.
• According to the World Health Organization (WHO), the
numbers of new cancer cases is expected to rise by
about 70% over the next 20 years.
• The most common sites of cancer among men are
lung, prostate, colon, rectum, stomach and liver.
• The most common sites of cancer among women are
breast, colon, rectum, lung, cervix and stomach.
How cancer spreads
Scientists reported in Nature Communications (October
2012 issue) that they have discovered an important clue
as to why cancer cells spread. It has something to do
with their adhesion (stickiness) properties. Certain
molecular interactions between cells and the scaffolding
that holds them in place (extracellular matrix) cause
them to become unstuck at the original tumor site, they
become dislodged, move on and then reattach
themselves at a new site.
The researchers say this discovery is important because
cancer mortality is mainly due to metastatic tumors,
those that grow from cells that have traveled from their
original site to another part of the body. These are
called secondary tumors. Only 10% of cancer deaths are
caused by the primary tumors.
The scientists, from the Massachusetts Institute of
Technology, say that finding a way to stop cancer cells
from sticking to new sites could interfere with
metastatic disease, and halt the growth of secondary
tumors.
Malignant cells are more agile than non -malignant
ones
Scientists from the Physical Sciences-Oncology Centers,
USA, reported in the journal Scientific Reports (April
2013 issue) that malignant cells are much “nimbler”
than non-malignant ones. Malignant cells can pass
more easily through smaller gaps, as well as applying a
much greater force on their environment compared to
other cells.
Professor Robert Austin and team created a new
catalogue of the physical and chemical features of
cancerous cells with over 100 scientists from 20
different centers across the United States.
The authors believe their catalogue will help oncologists
detect cancerous cells in patients early on, thus
preventing the spread of the disease to other parts of
the body.
Prof. Austin said "By bringing together different types of
experimental expertise to systematically compare
metastatic and non-metastatic cells, we have advanced
our knowledge of how metastasis occurs."
Causes of cancer
Cancer is ultimately the result of cells that
uncontrollably grow and do not die . Normal cells in the
body follow an orderly path of growth, division, and
death. Programmed cell death is called apoptosis, and
when this process breaks down, cancer begins to form.
Unlike regular cells, cancer cells do not experience
programmatic death and instead continue to grow and
divide. This leads to a mass of abnormal cells that
grows out of control.
What is cancer ? - Video
A short, 3D, animated introduction to cancer. This was
originally created by BioDigital Systems and used in the
Stand Up 2 Cancer telethon.
Genes - the DNA type
Cells can experience uncontrolled growth if there are
mutations to DNA, and therefore, alterations to the
genes involved in cell division. Four key types of gene
are responsible for the cell division process: oncogenes
tell cells when to divide, tumor suppressor genes tell
cells when not to divide, suicide genes control apoptosis
and tell the cell to kill itself if something goes wrong,
and DNA-repair genes instruct a cell to repair damaged
DNA.
Cancer occurs when a cell's gene mutations make the
cell unable to correct DNA damage and unable to
commit suicide. Similarly, cancer is a result of
mutations that inhibit oncogene and tumor suppressor
gene function, leading to uncontrollable cell growth.
Carcinogens
Carcinogens are a class of substances that are directly
responsible for damaging DNA, promoting or aiding
cancer. Tobacco, asbestos, arsenic, radiation such as
gamma and x-rays, the sun, and compounds in car
exhaust fumes are all examples of carcinogens. When
our bodies are exposed to carcinogens, free radicals are
formed that try to steal electrons from other molecules
in the body. Theses free radicals damage cells and
affect their ability to function normally.
Genes - the family type
Cancer can be the result of a genetic predisposition that
is inherited from family members. It is possible to be
born with certain genetic mutations or a fault in a gene
that makes one statistically more likely to develop
cancer later in life.
Cancer and other medical factors
As we age, there is an increase in the number of
possible cancer-causing mutations in our DNA. This
makes age an important risk factor for cancer. Several
viruses have also been linked to cancer such as: human
papillomavirus (a cause of cervical cancer), hepatitis B
and C (causes of liver cancer), and Epstein-Barr virus (a
cause of some childhood cancers). Human
immunodeficiency virus (HIV) - and anything else that
suppresses or weakens the immune system - inhibits
the body's ability to fight infections and increases the
chance of developing cancer.
Cancer classification
There are five broad groups that are used to classify
cancer.
Carcinomas are characterized by cells that cover
internal and external parts of the body such as lung,
breast, and colon cancer.
Sarcomas are characterized by cells that are located in
bone, cartilage, fat, connective tissue, muscle, and other
supportive tissues.
Lymphomas are cancers that begin in the lymph nodes
and immune system tissues.
Leukemias are cancers that begin in the bone marrow
and often accumulate in the bloodstream.
Adenomas are cancers that arise in the thyroid, the
pituitary gland, the adrenal gland, and other glandular
tissues.
Cancers are often referred to by terms that contain a
prefix related to the cell type in which the cancer
originated and a suffix such as -sarcoma, -carcinoma,
or just -oma. Common prefixes include:
Adeno- = gland
Chondro- = cartilage
Erythro- = red blood cell
Hemangio- = blood vessels
Hepato- = liver
Lipo- = fat
Lympho- = white blood cell
Melano- = pigment cell
Myelo- = bone marrow
Myo- = muscle
Osteo- = bone
Uro- = bladder
Retino- = eye
Neuro- = brain
Cancer diagnosis and staging
Early detection of cancer can greatly improve the odds
of successful treatment and survival. Physicians use
information from symptoms and several other
procedures to diagnose cancer.
Imaging techniques such as X-rays, CT scans , MRI
scans , PET scans , and
ultrasound scans are used regularly in order to detect
where a tumor is located and what organs may be
affected by it. Doctors may also conduct an
endoscopy, which is a procedure that uses a thin tube
with a camera and light at one end, to look for
abnormalities inside the body.
Extracting cancer cells and looking at them under a
microscope is the only absolute way to diagnose
cancer. This procedure is called a biopsy. Other types of
molecular diagnostic tests are frequently employed as
well. Physicians will analyze your body's sugars, fats,
proteins, and DNA at the molecular level. For example,
cancerous prostate cells release a higher level of a
chemical called PSA (prostate-specific antigen) into the
bloodstream that can be detected by a blood test.
Molecular diagnostics, biopsies, and imaging techniques
are all used together to diagnose cancer.
After a diagnosis is made, doctors find out how far the
cancer has spread and determine the stage of the
cancer. The stage determines which choices will be
available for treatment and informs prognoses. The
most common cancer staging method is called the TNM
system. T (1-4) indicates the size and direct extent of
the primary tumor, N (0-3) indicates the degree to
which the cancer has spread to nearby lymph nodes,
and M (0-1) indicates whether the cancer has
metastasized to other organs in the body. A small
tumor that has not spread to lymph nodes or distant
organs may be staged as (T1, N0, M0), for example.
TNM descriptions then lead to a simpler categorization
of stages, from 0 to 4, where lower numbers indicate
that the cancer has spread less. While most Stage 1
tumors are curable, most Stage 4 tumors are inoperable
or untreatable.
Recent developments on cancer diagnosis
Blood test could replace biopsy for cancer diagnosis
A simple blood test could be on the way to replacing
the biopsy as the gold standard for detecting cancer,
saving lives and money, according to researchers in the
UK. In their study, carried out on known or suspected
primary or secondary lung cancer who were about to
undergo surgery, the blood test was accurate in
predicting the presence of cancer cells in nearly 70% of
cases.
Symptoms of cancer
Cancer symptoms are quite varied and depend on where
the cancer is located, where it has spread, and how big
the tumor is. Some cancers can be felt or seen through
the skin - a lump on the breast or testicle can be an
indicator of cancer in those locations. Skin cancer
(melanoma) is often noted by a change in a wart or
mole on the skin. Some oral cancers present white
patches inside the mouth or white spots on the tongue.
Other cancers have symptoms that are less physically
apparent. Some brain tumors tend to present symptoms
early in the disease as they affect important cognitive
functions. Pancreas cancers are usually too small to
cause symptoms until they cause pain by pushing
against nearby nerves or interfere with liver function to
cause a yellowing of the skin and eyes called jaundice.
Symptoms also can be created as a tumor grows and
pushes against organs and blood vessels. For example,
colon cancers lead to symptoms such as constipation,
diarrhea, and changes in stool size. Bladder or prostate
cancers cause changes in bladder function such as
more frequent urination or infrequent urination.
Swollen or enlarged lymph nodes can be a symptom,
although lymph nodes can also become swollen when
fighting infection (cold or flu).
As cancer cells use the body's energy and interfere with
normal hormone function, it is possible to present
symptoms such as fever, fatigue, excessive sweating,
anemia, and unexplained weight loss. However, these
symptoms are common in several other maladies as
well. For example, coughing and hoarseness can point
to lung or throat cancer as well as several other
conditions.
When cancer spreads, or metastasizes, additional
symptoms can present themselves in the newly affected
area. Swollen or enlarged lymph nodes are common and
likely to be present when the cancer starts to spread.
If cancer spreads to the brain, patients may experience
vertigo, headaches, or seizures. Spreading to the lungs
may cause coughing and shortness of breath. In
addition, the liver may become enlarged and cause
jaundice and bones can become painful, brittle, and
break easily. Symptoms of metastasis ultimately depend
on the location to which the cancer has spread.
Treatments for cancer
Cancer treatment depends on the type of cancer, the
stage of the cancer (how much it has spread), age,
health status, and additional personal characteristics.
There is no single treatment for cancer, and patients
often receive a combination of therapies and palliative
care. Treatments usually fall into one of the following
categories: surgery, radiation, chemotherapy,
immunotherapy, hormone therapy, or gene therapy.
1) Surgery
Surgery is the oldest known treatment for cancer. If a
cancer has not metastasized, it is possible to
completely cure a patient by surgically removing the
cancer from the body. This is often seen in the removal
of the prostate or a breast or testicle. After the disease
has spread, however, it is nearly impossible to remove
all of the cancer cells. Surgery may also be instrumental
in helping to control symptoms such as bowel
obstruction or spinal cord compression.
Innovations continue to be developed to aid the surgical
process, such as the
iKnife that "sniffs" out cancer . Currently, when a tumor
is removed surgeons also take out a “margin” of healthy
tissue to make sure no malignant cells are left behind.
This usually means keeping the patients under general
anesthetic for an extra 30 minutes while tissue samples
are tested in the lab for “clear margins”. If there are no
clear margins, the surgeon has to go back in and
remove more tissue (if possible). Scientists from
Imperial College London say the iKnife may remove the
need for sending samples to the lab.
In a study carried out at Washington University School
of Medicine in 2014, researchers found a way of
visualizing cancer cells using high-tech glasses designed
to make it easier for surgeons to distinguish between
cancerous and healthy tissue. Viewed through the
glasses, cancer cells appear to glow blue under a
special light, thanks to a fluorescent marker injected in
the tumor that attaches only to cancerous and not to
healthy cells. Also, the lighter the shade of blue, the
more concentrated the cancer cells are.
Promising results of an early small trial at Duke
University Medical Center in Durham, NC have
suggested a new injectable agent that makes cancer
cells in a tumor fluoresce , could help surgeons remove
all of the cancerous tissue on the first attempt. Tests
continue to be carried out.
2) Radiation
Radiation treatment, also known as radiotherapy,
destroys cancer by focusing high-energy rays on the
cancer cells. This causes damage to the molecules that
make up the cancer cells and leads them to commit
suicide.
Radiotherapy utilizes high-energy gamma-rays that are
emitted from metals such as radium or high-energy x-
rays that are created in a special machine. Early
radiation treatments caused severe side-effects because
the energy beams would damage normal, healthy tissue,
but technologies have improved so that beams can be
more accurately targeted. Radiotherapy is used as a
standalone treatment to shrink a tumor or destroy
cancer cells (including those associated with leukemia
and lymphoma), and it is also used in combination with
other cancer treatments.
3) Chemotherapy
Chemotherapy utilizes chemicals that interfere with the
cell division process - damaging proteins or DNA - so
that cancer cells will commit suicide. These treatments
target any rapidly dividing cells (not necessarily just
cancer cells), but normal cells usually can recover from
any chemical-induced damage while cancer cells
cannot. Chemotherapy is generally used to treat cancer
that has spread or metastasized because the medicines
travel throughout the entire body. It is a necessary
treatment for some forms of leukemia and lymphoma.
Chemotherapy treatment occurs in cycles so the body
has time to heal between doses. However, there are still
common side effects such as hair loss, nausea, fatigue,
and vomiting. Combination therapies often include
multiple types of chemotherapy or chemotherapy
combined with other treatment options.
4) Immunotherapy
Immunotherapy aims to get the body's immune system
to fight the tumor. Local immunotherapy injects a
treatment into an affected area, for example, to cause
inflammation that causes a tumor to shrink. Systemic
immunotherapy treats the whole body by administering
an agent such as the protein interferon alpha that can
shrink tumors. Immunotherapy can also be considered
non-specific if it improves cancer-fighting abilities by
stimulating the entire immune system, and it can be
considered targeted if the treatment specifically tells the
immune system to destroy cancer cells. These therapies
are relatively young, but researchers have had success
with treatments that introduce antibodies to the body
that inhibit the growth of breast cancer cells. Bone
marrow transplantation (hematopoetic stem cell
transplantation) can also be considered immunotherapy
because the donor's immune cells will often attack the
tumor or cancer cells that are present in the host.
5) Hormone therapy
Several cancers have been linked to some types of
hormones, most notably breast and prostate cancer.
Hormone therapy is designed to alter hormone
production in the body so that cancer cells stop growing
or are killed completely. Breast cancer hormone
therapies often focus on reducing estrogen levels (a
common drug for this is tamoxifen) and prostate cancer
hormone therapies often focus on reducing testosterone
levels. In addition, some leukemia and lymphoma cases
can be treated with the hormone cortisone.
6) Gene therapy
The goal of gene therapy is to replace damaged genes
with ones that work to address a root cause of cancer:
damage to DNA. For example, researchers are trying to
replace the damaged gene that signals cells to stop
dividing (the p53 gene) with a copy of a working gene.
Other gene-based therapies focus on further damaging
cancer cell DNA to the point where the cell commits
suicide. Gene therapy is a very young field and has not
yet resulted in any successful treatments.
Using cancer -specific immune system cells to treat
cancer
Scientists from the RIKEN Research Centre for Allergy
and Immunology in Yokohama, Japan, explained in the
journal Cell Stem Cell (January 2013 issue) how they
managed to make cancer-specific immune system cells
from iPSCs (induced pluripotent stem cells) to destroy
cancer cells.
The authors added that their study has shown that it is
possible to clone versions of the patients’ own cells to
enhance their immune system so that cancer cells could
be destroyed naturally.
Hiroshi Kawamoto and team created cancer-specific
killer T-lymphocytes from iPSCs. They started off with
mature T-lymphocytes which were specific for a type of
skin cancer and reprogrammed them into iPSCs with the
help of “Yamanaka factors”. The iPSCs eventually
turned into fully active, cancer-specific T-lymphocytes -
in other words, cells that target and destroy cancer
cells.
Cancer prevention
Quitting smoking can significantly decrease your risk of
getting cancer.
Cancers that are closely linked to certain behaviors are
the easiest to prevent. For example, choosing not to
smoke tobacco or drink alcohol significantly lower the
risk of several types of cancer - most notably lung,
throat, mouth, and liver cancer. Even if you are a current
tobacco user, quitting can still greatly reduce your
chances of getting cancer.
Skin cancer can be prevented by staying in the shade,
protecting yourself with a hat and shirt when in the sun,
and using sunscreen. Diet is also an important part of
cancer prevention since what we eat has been linked to
the disease. Physicians recommend diets that are low in
fat and rich in fresh fruits and vegetables and whole
grains.
Certain vaccinations have been associated with the
prevention of some cancers. For example, many women
receive a vaccination for the human papillomavirus
because of the virus's relationship with cervical cancer.
Hepatitis B vaccines prevent the hepatitis B virus, which
can cause liver cancer.
Some cancer prevention is based on systematic
screening in order to detect small irregularities or
tumors as early as possible even if there are no clear
symptoms present. Breast self-examination,
mammograms, testicular self-examination, and Pap
smears are common screening methods for various
cancers.
Researchers from Northwestern University Feinberg
School of Medicine in Chicago reported in the journal
Circulation that the 7 steps recommended for protection
against heart disease can also reduce the risk of
developing cancer, . They include being physically active,
eating a healthy diet, controlling cholesterol, managing
blood pressure, reducing blood sugar and not smoking.
Targeting cancers for new drug therapies
Researchers at The Institute of Cancer Research
reported in the journal Nature Reviews Drug Discovery
(January 2013 issue) that they have found a new way
of rapidly prioritizing the best druggable targets online.
They managed to identify 46 previously overlooked
targets.
The researchers used the canSAR database together
with a tool and were able to compare up to 500 drug
targets in a matter of minutes. With this method, it is
possible to analyze huge volumes of data to discover
new drug targets, which can lead to the development of
effective cancer medications .
The scientists analyzed 479 cancer genes to determine
which ones were potential targets for medications. Their
approach was effective - they found 46 new potentially
“druggable” cancer proteins.
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