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Chapter Thirteen
Cancer: Understanding Risks and Means of Prevention
Learning Objectives
1. Identify and describe the most important ways to prevent cancer.
2. Briefly discuss the incidence of cancer today and why mortality has not fallen.
3. Define the following terms: cancer, tumor, benign tumor, malignant tumor, metastasis, and
xenoestrogen.
4. Explain the difference between inherited diseases and genetic diseases.
5. Describe the kinds of environmental agents that cause cancer.
6. Explain ways to prevent skin cancer.
7. Discuss some risk factors associated with breast cancer.
8. Describe how to do a breast self exam (BSE).
9. Describe how cigarette smoke contributes to cancer.
10. Discuss the association between diet and cancer.
11. Briefly describe the three medical treatments for cancer.
12. Describe several coping mechanisms for someone with cancer.
13. Explain the risks and benefits of being tested for cancer susceptibility gene.
Key Terms
Basal cell carcinoma (303)
Benign tumor (291)
Biopsy (293)
Cancer (291)
Cancer-susceptibility gene (294)
Chemical carcinogen (297)
Chemotherapy (305)
Epidemiology (294)
Ionizing radiation (296)
Malignant tumor (291)
Mammogram (300)
Melanoma (303)
Mesothelioma (297)
Metastasis (292)
Mutation (295)
Pathologist (292)
Prostate-specific antigen (PSA) test (302)
Radiation therapy (305)
Squamous cell carcinoma (303)
Tumor (291)
Tumor viruses (296)
Xenoestrogens (298)
Chapter Summary
Cancer is the general term used to describe a group of different diseases. In the United States,
one of two men and one of three women will develop some type of cancer. In 2000,
approximately 556,000 Americans died from cancer.
The majority of cancers are preventable. Prevention begins with adopting healthy lifestyles, e.g.,
avoiding cigarette smoking and eating a nutritious diet. In addition, screening and early detection
of cancer may increase the likelihood of curing the disease. Screening tests for many forms of
cancer are recommended when a person reaches the age at which susceptibility increases.
Lecture Outline
Incidence of Various Cancers
• Hodgkin’s disease and cancers of the stomach, uterus, cervix, and testis have declined
significantly in recent years.
• Cancers of the lung, skin, liver, prostate, and kidney and non-Hodgkin’s lymphoma have all
increased in frequency.
• The most serious increase is in the rate of lung cancer in both men and women due to smoking.
Cancer
• The unregulated multiplication of specific cells in the body.
• Cancer is a group of more than 100 different diseases.
• If a normal cell begins to grow abnormally and reproduce too rapidly, a mass of abnormal cells
eventually becomes a tumor.
• If cells remain localized at the site of origin and if the cells multiply slowly, the tumor is called
a benign tumor.
—Some benign tumors are cysts, warts and moles.
—Benign tumors are usually removed surgically and generally are not a threat to life.
—If all of the cells are removed, the tumor will not re-grow.
• Malignant tumors are composed of cells that grow rapidly, have abnormal properties, and
invade normal cells.
• Malignant cells have altered shapes.
• A pathologist (a physician who specializes in identifying the causes of diseases) can determine
whether the cells removed from a tumor are abnormal and to what degree.
• The cells of most malignant tumors undergo metastasis, a process in which cells detach from
the original tumor, enter the lymphatic system and bloodstream, are carried to other organs, and
begin to grow there.
• Cancers are medically classified according to the organ or tissue in which the tumor originates.
• There are four major categories:
—Carcinomas (cancers of epithelial tissues, skin, nerves, breasts)
—Sarcomas (cancers of connective tissues, bone, muscles, fat, and blood vessels)
—Leukemias (cancers of organs and tissues that form blood cells)
—Lymphomas (similar to leukemias)
• About 50% of all human cancers originate in one of four organs
—Lung
—Breast
—Prostate
—Colon
Four Stages of Cancer Development
• Stage I: Cancer cells can be distinguished from normal cells.
• Stage II: Cancer cells begin to metastasize and may migrate to nearby lymph nodes.
• Stage III: Cancer cells have spread throughout the body, and tumors may have started to grow
in other organs.
• Stage IV: Tumors are found throughout the body and usually are resistant to treatment; often a
terminal stage.
Causes of Cancer
• Scientific research indicates that 90% to 95% of all cancers (including breast, lung, stomach,
colon, skin, and prostate cancers) are not hereditary.
Environmental Factors
• It is difficult to pinpoint a single cause of cancer, but certain environmental factors are
associated with the occurrence of particular cancers.
• Epidemiological studies show that 80% to 90% of cancers are caused by exposure to
environmental factors known to increase the risk of cancer.
• Three classes of environmental agents:
—Ionizing radiation, comprising x-rays, ultraviolet light, and radioactivity, all of which can
damage cells and chromosomes
—Tumor viruses
—Chemical carcinogens
Tumor Viruses
• Four tumor viruses identified in human cancers:
—Liver cancer and hepatitis B virus
—Genital and cervical cancer and human papillomavirus
—Leukemia and lymphoma and human T-cell leukemia-lymphoma virus
—Cancer of the nose in Africans and Epstein-Barr virus
Chemical Carcinogens
• Environmental chemicals can interact with cells to initiate cancer.
—Cigarette smoke
—Pesticides
—Asbestos
—Heavy metals
—Benzene
—Nitrosamines
Xenoestrogens
• Chemicals found in the environment mimic the body’s estrogen hormone and may cause breast
cancer.
• Substances that contain xenoestrogens:
—Pesticides
—Polychlorinated biphenyls (PCBs)
—Biphenol-A
—Gasoline vapor
Common Cancers: Lung Cancer
• Lung cancer causes more deaths among men and women than any other form of cancer.
• Lung cancer could be prevented almost completely if people would stop (or never start)
smoking.
• Lung cancer rate is increasing in other nations.
Common Cancers: Breast Cancer
• Both men and women can develop breast cancer, but it occurs very rarely among men.
• Factors that have been proposed as contributing to the increased rate of breast cancer include:
—Increased weight
—Less exercise
—Increased dietary fat
• Other factors that increase risk:
—Having a mother who had breast cancer before age 60
—Experiencing menarche before age 14
—Having your first child after age 30 or no biological children
—Experiencing menopause after age 55
—Having benign breast disease
—Using estrogen replacement therapy after age 55
—Consuming more than 3 ounces of alcohol a day
—Having inherited BRCA1 or BRCA2 gene
• Monthly breast self-exams beginning at age 20 aid early detection.
• Mammograms every one to two years for women in their 40s.
• The drug tamoxifen can be used for breast cancer treatment as well as protection.
Common Cancers: Prostate Cancer
• Prostate cancer occurs primarily in men over age 65.
• Early diagnosis relies on two tests:
—Finger rectal exam
—Prostate-specific antigen (PSA) test detects a protein in blood that is associated with
abnormal growth of the prostate gland.
Common Cancers: Skin Cancer
• Melanoma is a malignant form of skin cancer.
• Fifth most frequently diagnosed cancer among Americans.
• Exposure to sunlight is the primary cause of all forms of skin cancer.
• Basal cell carcinoma and squamous cell carcinoma are usually not life-threatening; the
abnormal cells can be removed by:
—Surgery
—Scraping
—Freezing
—Burning
• Remember the ABCD rule when examining your skin for moles that could be melanoma.
—Asymmetry
—Border
—Color
—Diameter
Common Cancers: Colon Cancer
• Colon cancer affects men and women equally.
• Causes about 60,000 deaths annually in the U.S.
• No screening test for colon cancer is completely accurate.
• Certain inherited genes are known to increase risk of colon cancer.
Diet and Cancer Risk
• Many studies suggest that diet is associated with cancer.
• Certain dietary choices may help prevent cancer.
• Vitamin C
• Scientists speculate that there may be a link between cancer and the highly processed foods
that are common in today’s diets.
Cancer Treatments
• There are three medical treatments for cancer.
—Surgical removal of the tumor
—Radiation therapy to destroy cancer cells
—Chemotherapy, or the use of toxic chemicals (drugs) to kill cancer cells.
Experimental Cancer Treatments
• Medical researchers are looking for ways to enhance the body’s immune system so that
abnormal cells are eliminated and do not compromise the body’s system.
• Angiogenesis occurs when a tumor develops a network of new blood vessels to support it with
nutrients; drugs that inhibit angiogenesis are being developed and tested in clinical trials.
Coping with a Diagnosis of Cancer
• Can be difficult because of:
—Denial on the part of the patient or family
—The need for surgery or other treatment
—The need to face death of the patient
• The coping strategies for dealing with the emotional distress of many chronic or fatal illnesses
are similar.
• Coping with cancer requires conviction, courage and belief that a cure is possible.
Study Guide and Self Assessment Workbook
13.1 My Cancer Risks
13.2 My Environmental Cancer Risks
Additional Resources
American Cancer Society
1599 Clifton Rd, NE
Atlanta, GA 30329-4251
(800) ACS-2345
www.cancer.org
Cancer Connection
H&R Block Building
4410 Main
Kansas City, MO 64111
www.cancer-connection.com
National Cancer Institute
Cancer Information Service
Building 31, Room 10A24
Bethesda, MD 20892
(800)4-CANCER
www.nci.nih.gov
www.cancer.gov/clinicaltrials (clinical trials)