What is cancer?
Cancer is a group of many related diseases that begin in cells, the body's basic building blocks.
To understand cancer, it is helpful to know what happens when normal cells become cancerous.
The body is made up of many types of cells. Normally, cells grow and divide to produce more
cells as they are needed to keep the body healthy. Sometimes, this orderly process goes wrong.
New cells form when the body does not need them, and old cells do not die when they should.
The extra cells form a mass of tissue called a growth or tumor. Not all tumors are cancerous;
tumors can be benign or malignant.
Benign tumors are not cancer. They can often be removed and, in most cases, they do not come
back. Cells in benign tumors do not spread to other parts of the body. Most important, benign
tumors are rarely a threat to life.
Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control or
order. Cancer cells invade and destroy the tissue around them. Cancer cells can also break away
from a malignant tumor and enter the bloodstream or lymphatic system.
Blood vessels include a network of arteries, capillaries, and veins through which the blood
circulates in the body. The lymphatic system carries lymph and white blood cells through
lymphatic vessels (thin tubes) to all the tissues of the body. By moving through the bloodstream
or lymphatic system, cancer can spread from the primary (original) cancer site to form new
tumors in other organs. The spread of cancer is called metastasis.
What causes cancer?
Cancer is caused by changes in genes that normally control the growth and death of cells.
Certain lifestyle and environmental factors can change some normal genes into genes that allow
the growth of cancer. Many gene changes that lead to cancer are the result of tobacco use,
diet, exposure to ultraviolet (UV) radiation from the sun, or exposure to carcinogens (cancer-
causing substances) in the workplace or in the environment. Some gene alterations are inherited
(from one or both parents). However, having an inherited gene alteration does not always mean
that the person will develop cancer; it only means that the chance of getting cancer is
increased. Scientists continue to examine the factors that may increase or decrease a person's
chance of developing cancer.
Cancer is not contagious. A person cannot catch cancer from someone who has this disease.
Can cancer be prevented?
Although there is no guaranteed way to prevent cancer, people can reduce their risk (chance) of
developing cancer by:
not using tobacco products
choosing foods with less fat and eating more vegetables, fruits, and whole grains
exercising regularly and maintaining a lean weight
avoiding the harmful rays of the sun, using sunscreen, and wearing clothing that protects the
talking with a doctor about the possible benefits of drugs proven to reduce the risk of certain
What are some of the common signs and symptoms of cancer?
Cancer can cause a variety of symptoms. Possible signs of cancer include the following:
new thickening or lump in the breast or any other part of the body
new mole or an obvious change in the appearance of an existing wart or mole
a sore that does not heal
nagging cough or hoarseness
changes in bowel or bladder habits
persistent indigestion or difficulty swallowing
unexplained changes in weight
unusual bleeding or discharge
How is cancer treated?
Cancer treatment can include surgery, radiation therapy, chemotherapy, hormone therapy, and
biological therapy. The doctor may use one method or a combination of methods, depending on
the type and location of the cancer, whether the disease has spread, the patient's age and
general health, and other factors. Because treatment for cancer can also damage healthy cells
and tissues, it often causes side effects.
Surgery is an operation to remove cancer.
Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells in a
targeted area. Radiation can be given externally by a machine that aims radiation at the tumor
area. It can also be given internally; needles, seeds, wires, or catheters containing a radioactive
substance are placed directly in or near the tumor. Radiation treatments are painless. The side
effects are usually temporary, and most can be treated or controlled. Patients are likely to feel
very tired, especially in the later weeks of treatment. Radiation therapy may also cause a
decrease in the number of white blood cells, which help protect the body against infection. With
external radiation, it is also common to have temporary hair loss in the treated area and for the
skin to become red, dry, tender, and itchy.
Chemotherapy is the use of drugs that kill cancer cells throughout the body. Healthy cells can
also be harmed, especially those that divide quickly. The side effects of chemotherapy depend
mainly on the drug and the dose the patient receives. Hair loss is a common side effect of
chemotherapy. Anticancer drugs may also cause temporary fatigue, poor appetite, nausea and
vomiting, diarrhea, and mouth and lip sores.
Hormone therapy is used to treat certain cancers that depend on hormones for their growth. It
works by keeping cancer cells from getting or using the hormones they need to grow. This
treatment may include the use of drugs that stop the production of certain hormones or that
change the way hormones work.
Hormone therapy can cause a number of side effects. Patients may feel tired, or have fluid
retention, weight gain, hot flashes, nausea and vomiting, changes in appetite, and, in some
cases, blood clots. Hormone therapy may also cause bone loss in premenopausal women.
Depending on the type of hormone therapy used, these side effects may be temporary, long
lasting, or permanent.
Biological therapy uses the body's immune system, directly or indirectly, to fight disease and to
lessen some of the side effects of cancer treatment. Monoclonal antibodies, interferon,
interleukin-2, and colony-stimulating factors are some types of biological therapy.
The side effects caused by biological therapy vary with the specific treatment. In general, these
treatments tend to cause flu-like symptoms, such as chills, fever, muscle aches, weakness, loss
of appetite, nausea, vomiting, and diarrhea. Patients also may bleed or bruise easily, get a skin
rash, or have swelling. These problems can be severe,