Senin, 11 April 2011

Understanding Cancer

The word cancer refers to changes in the body's cells that allow these cells to grow out of control. These cells often grow very fast, crowding out normal cells in the area around the cancer. Cancer cells also have the ability to spread, ormetastasize, to other organs in the body, causing additional damage in areas of the body not connected with the original cancer site.

Cancer can occur in almost any cell. It begins when the cell's DNA, or genetic information, becomes damaged. DNA controls all cell functions, including when to divide (reproduce) and when to die. When DNA is damaged, some cells become unstable, dividing more often than normal cells or failing to die when they should. Most of the time, the body's immune system finds these damaged cells and destroys them. However, if this normal process does not happen, atumor can begin.

A tumor is a mass, or collection, of abnormal cells. Tumors can be eitherbenign or malignant.
• Benign tumors (noncancerous) can grow and expand in size, but they do not invade surrounding tissue or travel to other areas of the body.

• Malignant tumors (cancerous) are made up of cells that are very different from normal cells. These cancer cells can, and often do, invade nearby tissues. They also can travel away from the original (primary) site to other parts of the body, causing tumors in other organs (distant sites) in a process called metastasis.

Types of Cancer

A solid tumor is a localized mass of abnormal cells. Solid tumors are divided into broad categories based on the type of tissue where the cancer first occurred; carcinomas, sarcomas, and lymphomas are examples of solidtumors. Table 1-1 shows different types of cancer and where they originate.1 In addition, cancers are defined by the type of cell or organ where they came from. For example, a cancer beginning in the colon is called colon cancer or coloncarcinoma. Cancers originating in certain cells found in the skin are called basal cell carcinomas

Not all cancers, however, form solid tumors. Cancers of the blood or bone marrow (hematologic malignancies), are often referred to a "liquid tumors" because they do not form a defined mass of abnormal cells like solid tumors do. Examples of liquid tumors include leukemia and multiple myeloma.

Table 1-1: Types of Cancer1
Type of CancerCell Type of Origin
CarcinomaSkin or tissues that line or cover internal organs
SarcomaBone, cartilage, fat muscle, blood vessels, or other connective or supportive tissue
Central nervous system cancerTissues of the brain and spinal cord
LymphomaCells of the immune system
Leukemia andmyelomaBlood forming tissue, such as the bone marrow

Causes of Cancer

Although every patient and family member wants to know what may have caused their cancer, the reason a particular person developed cancer is, in many cases, not well understood.

Cancer occurs because normal cells become abnormal due to harmful mutations in one or more genes.4 While the reasons that cells become abnormal are not completely understood, certain known risk factors increase the chance that genes will become mutated. Still, not all people who have risk factors will develop cancer—in fact, most people with a particular risk factor do not develop cancer. On the other hand, some people who have no known risk factors will get cancer. Separate risk factors may combine over time to cause normal cells to become abnormal.

Known Risk Factors for Cancer

Below are some known risk factors for cancer.
  • • An individual person's risk of cancer increases with advancing age, even though many cancers can develop at any age.
  • • Some gene mutations that increase the risk of cancer can be passed from parent to child.
  • • Menopausal hormone therapy with estrogen and/or progestin can increase the risk of breast cancer.
  • • Infection with some viruses and bacteria can increase the risk of cancer. Even so, cancer is not contagious. Examples of viruses and bacteria that can increase the risk of cancer include:
  • o Infection with certain types of the human papillomavirus (HPV) is a major cause of cervical cancer.
  • o Infection with the Epstein-Barr virus is associated with an increased risk of lymphoma.
  • o The Helicobacter pylori bacterium can cause some kinds of stomach cancer.
  • • Exposure to ultraviolet radiation from the sun, sunlamps, and tanning booths can cause skin damage that increases the risk of skin cancer.
  • • Exposure to ionizing radiation, such as radon gas, x-rays, and radioactive fallout, can increase the risk of many kinds of cancer. The risk of cancer from low-dose x-rays is very small.
  • • Exposure to chemicals such as benzene, metals such as nickel, or substances such as asbestos has been shown to increase the risk of cancer.
  • • Poor diet, lack of physical activity, or being overweight may increase the risk of developing many kinds of cancer.
  • • Having more than two alcoholic drinks per day over many years may increase the risk of developing cancer of the mouth, throat, esophagus, larynx, liver, or breast.
  • • Tobacco smoking increases the risk of developing cancer in the lungs, throat, voice box, mouth, esophagus, bladder, kidney, stomach, pancreas, or cervix. People who smoke are also more likely to develop a cancer of the blood cells called acute myeloid leukemia. Use of snuff or chewing tobacco increases the risk of developing cancer of the mouth.

Treating Cancer

Because cancer is a complicated disease that takes many different forms, it is treated in many different ways. Treatment is tailored to the specific needs of the patient.

Cancer treatments vary depending upon four main factors:
• Type of cancer
• Stage of cancer
• Your overall condition
• Goal of treatment

Your doctor will determine the stage and grade of your cancer. Learn aboutstaging and grading of cancer.

The goals of cancer treatment also vary:
• Cure
• Prolong life
• Reduce unwanted symptoms or effects of the cancer

Your doctor may recommend one or more treatments, also referred to asmodalities, to achieve your goals. Increasingly, it is common to use several treatments at the same time or in sequence in order to prevent both local recurrence and recurrence throughout the body. This is referred to as a multi-modality treatment. Modalities include chemotherapy, surgery, radiation therapy, biological therapy, and hormone therapy. Chemotherapy is one of the best ways to help you achieve your treatment goals. Find out about treating cancer with chemotherapy.

Your doctor may also discuss combining your chemotherapy with other treatments. Learn about treating cancer in other ways.

Reasons to Be Optimistic

As you move beyond the initial shock of learning that you have cancer to begin the journey of surviving cancer, you have many good reasons to be optimistic. Science and medicine have made—and continue to make—tremendous progress in treating cancer and in making treatments more manageable, both physically and emotionally. Chemotherapy is one of the most significant advances in the history of medicine. For millions of people, it helps treat their cancer effectively and helps them enjoy full, productive lives. However, chemotherapy is not without side effects and risks. Learn about managingchemotherapy side effects

No one would call having cancer or undergoing chemotherapy a normal experience, but by proactively managing your treatment with your doctor, including potential side effects, you can help ensure that your life stays as close to normal as possible.

Don't forget: You are not alone. Fighting cancer is a team effort that involves family, friends, and your healthcare team.

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