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Cancer 101

What is cancer? Cancer is a group of many related diseases in which abnormal cells develop, divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. 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 importantly, 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. They can also break away from a malignant tumor and enter the bloodstream or lymphatic system. 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. There are many factors that increase the chance of developing cancer, including lifestyle, environment, and genetic risk factors. There are also certain viruses that increase the risk of developing cancer.

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, obesity, lack of physical activity, exposure to ultraviolet (UV) radiation from the sun, or exposure to carcinogens (cancer-causing substances) in the workplace or in the environment. Viruses, such as the human papillomavirus (HPV), hepatitis B and C (HepB and HepC), and human immunodeficiency virus (HIV), increase the risk of some types of cancer. However, cancer itself is not contagious. A person cannot catch cancer from someone who has this disease.

Changes, called alterations or mutations, in certain genes make some people more susceptible to developing some types of cancer such as breast, prostate and ovarian cancer. Some genetic 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.

What does it mean when I am genetically at risk for developing cancer? Genetic risk factors can lead to development of hereditary forms of cancer. Inherited alterations in the genes called BRCA1 and BRCA2 (short for breast cancer 1 and breast cancer 2) are involved in many cases of hereditary breast and ovarian cancer.

As with breast cancer, familial history is a major risk factor in prostate cancer. 5 to 10 percent of prostate cancer cases are believed to be due primarily to high-risk inherited genetic factors or prostate cancer susceptibility genes. A family history of a brother or father with prostate cancer increases the risk of prostate cancer by two- to three-fold, and the risk is inversely related to the age of the affected relative.

How does smoking relate to cancer? Tobacco smoke contains thousands of chemical agents, including over 60 substances that are known to cause cancer. Smoking harms nearly every major organ of the body. Cigarette smoking is directly responsible for approximately 30 percent of all cancer deaths annually in the United States and 87 percent of lung cancer deaths. Lung cancer is the leading cause of cancer death in both men and women. Smoking is also responsible for most cancers of the larynx, oral cavity and pharynx, esophagus, and bladder. In addition, it is a cause of kidney, pancreatic, cervical, and stomach cancers, as well as acute myeloid leukemia.

Cigarette smoking also causes chronic diseases such as emphysema, chronic bronchitis, cardiovascular disease, stroke, and cataracts. Smoking during pregnancy can increase the risk of stillbirth, low birthweight, Sudden Infant Death Syndrome (SIDS), and other serious pregnancy complications (2). The health risks caused by cigarette smoking are not limited to smokers. Exposure to secondhand smoke, or environmental tobacco smoke (ETS), significantly increases the risk of lung cancer and heart disease in nonsmokers, as well as several respiratory illnesses in young children. Quitting smoking greatly reduces a person's risk of developing the diseases mentioned, and can limit adverse health effects on the developing child.

Am I at a higher risk for developing cancer because of race or ethnicity? Cancer affects people of all racial and ethnic groups. However, there are disparities between groups. African Americans are more likely to develop and die from cancer than any other racial and ethnic group. Additionally, certain racial/ethnic groups experience higher rates for specific cancers than other groups. Many of the differences in cancer incidence and mortality rates among racial and ethnic groups may be due to factors associated with social class rather than ethnicity. Socioeconomic status (SES) appears to play a major role in the differences in cancer incidence and mortality rates, risk factors, and screening prevalence among racial and ethnic minorities. Moreover, studies have found that SES, more than race, predicts the likelihood of a groups access to education, certain occupations, and health insurance, as well as income level and living conditions, all of which are associated with a persons chance of developing and surviving cancer.

Are there ways to prevent cancer? This risk of developing cancer can be reduced by:

  • not using tobacco products- (The most consistent finding, over decades of research, is the strong association between tobacco use and cancers of many sites. Hundreds of studies have confirmed this. Lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking followed by decreases in lung cancer death rates in men.)
  • choosing foods with less fat and eating more vegetables, fruits, and whole grains (Obesity is associated with colon, breast, endometrial, and possibly other cancers)
  • avoiding excessive alcohol drinking (Excessive alcohol consumption is associated with increased risk of oral, esophageal, breast, and other cancers)
  • exercising regularly and maintaining a lean weight (Physical inactivity is associated with increased risk of colon, breast, and possibly other cancers)
  • avoiding the harmful rays of the sun, using sunscreen, and wearing clothing that protects the skin (Over exposure to harmful rays is associated skin cancer)
  • Avoiding exposure to ionizing radiation and ultraviolet radiation, certain occupational and chemical exposures, and infectious agents
  • talking with a doctor about the possible benefits of drugs proven to reduce the risk of certain cancers

Although many risk factors can be avoided, some, such as inherited conditions, are unavoidable. However, it is helpful to be aware of them. People who have an increased likelihood of developing cancer can help protect themselves by avoiding risk factors whenever possible and by getting regular checkups so that, if cancer develops, it is likely to be found and treated early.

What are some of the common signs and symptoms of cancer? Cancer can cause a variety of symptoms. However, it is important to get regular screenings because sometimes there are no symptoms until later stages of cancer. 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

When these or other symptoms occur, they are not always caused by cancer. They can be caused by infections, benign tumors, or other problems. It is important to see a health provider about any of these symptoms or about other physical changes. Only a health provider can make a diagnosis. A person with these or other symptoms should not wait to feel pain because early cancer usually does not cause pain.

Why is cancer screening important? Treatment is often more effective when cancer is detected early. Screening exams, such as sigmoidoscopy or the fecal occult blood test, mammography, and the Pap test, can detect precancerous conditions, which can be treated before they turn into cancer, and early-stage cancer.

What is meant by cancer "stage"?

Staging describes the extent or severity of an individual's cancer based on the extent of the original (primary) tumor and the extent of spread in the body. Staging is important because:

  • Staging helps the doctor plan a person's treatment.
  • The stage can be used to estimate the person's prognosis (likely outcome or course of the disease).
  • Knowing the stage is important in identifying clinical trials (research studies) that may be suitable for a particular patient.

StageDefinition
Stage 0Carcinoma in situ (early cancer that is present only in the layer of cells in which it began).
Stage I, Stage II, and Stage IIIHigher numbers indicate more extensive disease: greater tumor size, and/or spread of the cancer to nearby lymph nodes and/or organs adjacent to the primary tumor.
Stage IVThe cancer has spread to another organ.


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 stage, type and location of the cancer, whether the disease has spread, the patient's age and general health, and other factors.

For more information on cancer:

National Cancer Institute
www.cancer.gov)

National Institute of Environmental Health Sciences: Carcinogens
http://ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-7FCE50709CB4C932

American Cancer Society
www.cancer.org Exit Disclaimer)



Content Last Modified: 11/23/2005 2:25:00 PM
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