Colon cancer
happens when tumorous growths develop in the large intestine. It is the third
most common type of cancer in the United States.
The
colon, or large intestine, is where the body extracts water and salt from solid
wastes. The waste then moves through the rectum and exits the body through the
anus.
It is also the third most
common cause of cancer-related death, and in 2017, 95,520 new diagnoses are expected to
occur in the United States (U.S.). However, advances in diagnosis, screening,
and treatment have led to steady improvements in survival.
Regular screenings are
recommended after the age of 50 years.
Colon cancer and rectal cancer may occur
together. This is called colorectal cancer.
Rectal cancer originates in the rectum, which is the last several inches of the
large intestine, closest to the anus.
Fast facts on colon cancer:
Here
are some key points about colon cancer. More detail is in the main article.
Colon
cancer affects the large intestine and it usually starts with polyps in the
wall of the intestine.
Symptoms
may not appear until a later stage, but if they do, gastrointestinal problems
are common symptoms.
Treatment
involves a combination of chemotherapy, radiation therapy, and
surgery, possibly resulting in a colostomy.
A
healthy lifestyle with a high-fiber, low-fat diet can help prevent colon
cancer, and screening can detect it in the early stages.
Symptoms
and signs
There are often no symptoms in the earliest
stages, but symptoms may develop as the cancer advances.
They include:
diarrhea or constipation
changes
in stool consistency
loose
and narrow stools
rectal
bleeding or blood in the stool
abdominal
pain, cramps, bloating, or gas
pain
during bowel movements
continual
urges to defecate
weakness
and fatigue
unexplained
weight loss
irritable bowel syndrome (IBS)
iron
deficiency anemia
If the cancer spreads to a new
location in the body, additional symptoms can appear in the new area. The liver
is most commonly affected.
Stages
There are different ways of
staging cancer. The stages depend on how far the cancer has spread.
Here is a brief summary of a
commonly used four-stage account of where the cancer
is at the beginning of each stage.
Stage 0: The
cancer is in a very early stage. It is known as carcinoma in situ.
It has not grown further than the inner layer of the colon.
Stage 1: The
cancer has grown into the next layer of tissue, but it has not reached the
lymph nodes or other organs.
Stage 2: The
cancer has reached the outer layers of the colon, but it has not spread beyond
the colon.
Stage 3: The
cancer has grown through outer layers of the colon and it has reached one to
three lymph nodes. It has not spread to distant sites.
Stage 4: The
cancer has reached other tissues beyond the wall of the colon. As stage 4
progresses, the cancer reaches distant parts of the body.
Cancer develops progressively.
Each stage is not fixed but describes a phase during which certain developments
take place.
Treatment
Treatment will depend on the
type and stage of the cancer, and the age, health status, and other
characteristics of the patient.
There is no single treatment for
any cancer, but the most common options for colon cancer are surgery,
chemotherapy, and radiation therapy.
Treatments seek to remove the
cancer and relieve any painful symptoms.
Surgery
Surgery to remove part or all of the colon is
called a colectomy. The surgeon removes the part of the colon containing the
cancer and the surrounding area.
Nearby lymph nodes are also
usually removed. The healthy portion of the colon will either be reattached to
the rectum or attached to a stoma depending on the extent of the colectomy.
A stoma is an opening made in
the wall of the abdomen. Waste will pass into a bag, removing the need for the
lower part of the colon. This is called a colostomy.
Some small, localized cancers
can be removed using endoscopy.
Laparoscopic surgery, using
several small incisions in the abdomen, may be an option to remove larger
polyps.
Palliative surgery may relieve
symptoms in cases of untreatable or advanced cancers. The aim is to relieve any
blockage of the colon and manage pain, bleeding, and other symptoms.
Chemotherapy
Chemotherapy administers
chemicals that interfere with the cell division process by damaging proteins or
DNA in order to damage and kill cancer cells.
These treatments target any
rapidly dividing cells, including healthy ones. The healthy cells can usually
recover from any chemically-induced damage, but cancer cells cannot.
Chemotherapy is generally used
to treat cancer that has spread because the medicines travel through the whole
body. Treatment occurs in cycles, so the body has time to heal between doses.
Common side effects include:
hair loss
nausea
fatigue
vomiting
Combination therapies often mix
multiple types of chemotherapy or combine chemotherapy with other treatments.
Radiation
Radiation treatment damages and
kills cancer cells by focusing high-energy gamma-rays on them.
Radioactive gamma-rays are
emitted from metals such as radium, or from high-energy x-rays. Radiotherapy
can be used as a standalone treatment to shrink a tumor or destroy
cancer cells, or alongside other cancer treatments.
Radiation treatments are not
often used until a later stage. They may be employed if early stage rectal
cancer has penetrated the wall of the rectum or traveled to nearby lymph nodes.
Side effects may include:
mild
skin changes resembling sunburn or suntan
nausea
vomiting
diarrhea
fatigue
appetite
and weight loss
Most side effects resolve a few
weeks after completing treatment.
Source: Medical News Today
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