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Chapter 13
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 out of two men and one out 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
Cancer: Understanding Risks and Means of Prevention
•
One in two men and one in three women will develop some form of cancer in their
lifetime.
•
Most cancers are preventable with a healthy lifestyle.
– Avoid cigarette smoke and tobacco in any form.
– Maintain a healthy weight and be physically active.
– Maintain good nutrition.
Understanding Cancer
•
“Cancer” from the Latin word meaning crab
– Unregulated multiplication of specific cells in the body.
– A tumor develops when a normal body cell grows abnormally and reproduces too
rapidly.
– Benign tumors do not spread to other parts of the body.
– Malignant tumors are composed of cells that multiply rapidly, have abnormal
properties, and invade other normal tissue.
– The cells of most malignant tumors undergo metastasis, a process where the cells
detach from the original tumor, enter the lymphatic system and bloodstream, and
are carried to other organs.
•
Cancers are medically classified according to the organ or tissue in which
the tumor originates.
•
There are four major categories:
– Carcinomas (e.g., cancers of epithelial tissues, skin, nerves, breasts)
– Sarcomas (e.g., cancers of connective tissues, bone, muscles, fat, and blood
vessels)
– Leukemias (e.g., cancers of organs and tissues that form blood cells)
– Lymphomas (similar to leukemias)
•
Fifty percent of all human cancers originate in one of four organs:
– Lungs
– Breast
– Prostate
– Colon
•
Stages of Cancer
– 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: Often a terminal stage; tumors are found throughout the body and
usually are resistant to treatment.
Causes of Cancer
•
90–95% of all cancers are not inherited from parents.
•
Genes can be altered by environmental agents, which transform cells into cancer cells.
Cancer is a genetic disease but not an inherited disease.
– Cancer-susceptibility genes
– Makes a person more vulnerable to environmental factors that contribute to the
risk of developing cancer
– Being identified as a carrier does not guarantee that you will have cancer.
Environmental Factors That Cause Cancer
•
It is difficult to pinpoint a single cause of cancer, but certain environmental factors are
strongly 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.
– For example, smoking cigarettes = 10–20 times higher risk later in life
Environmental Factors That Cause Cancer
•
Three Classes of Environmental Agents
– Ionizing Radiation
– Infectious Microorganisms
– Cancer-Causing Chemicals (Carcinogens)
•
Three Classes of Environmental Agents
– Ionizing Radiation
•
X-rays, UV light, and radioactivity whose energy can damage cells and
chromosomes.
•
UV light—UVA and UVB wavelengths are both dangerous.
– Infectious Mircoorgansims
•
“Tumor Viruses”
•
Only four viruses have been associated with specific human cancers; in
most people, infection by these viruses will not cause cancer.
•
Hepatitis B and C (liver cancer)
•
Papillomavirus (genital and cervical cancer)
•
Human T-cell leukemia-lymphoma virus (leukemia and lymohoma)
•
Epsten-Barr virus (cancer of the nose or pharynx)
– Chemical Carcinogens
•
Environmental chemicals that can interact with cells to initiate cancer:
– Tobacco
– Pesticides
– Asbestos
– Heavy metals
– Benzene
– Nitrosamines
•
Three Classes of Environmental Agents
– Chemical Carcinogens
•
Mesothelioma—a rare form of lung cancer that only occurs among
persons exposed to asbestos fibers.
•
•
Industry exposure risk is low compared to tobacco and diet.
Do Xenoestrogens Cause Cancer?
– Chemicals found in the environment that mimic estrogen and aid the development
of cancer, specifically breast cancer
– Substances that contain xenoestrogens:
•
DDT
•
Pesticides
•
Polychlorinated biphenyls (PCBs)
•
Bisphenol-A (BPA)
•
Gasoline vapor
– Eating broccoli, cabbage, and soy products may help counteract the effects of
xenestrogens.
Facts About Common Cancers
•
Lung Cancer
– Lung cancer causes more deaths among men and women than any other form
of cancer.
– Lung cancer could almost be completely prevented if people would stop (or never
start) smoking.
•
Main cause of 80–90% of lung cancers
– Lung cancer rate is increasing in other nations.
•
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 having no biological children
•
Experiencing menopause after age 55
•
Having benign breast disease
•
Having estrogen replacement therapy after age 55
•
Consuming more than 3 ounces of alcohol a day
•
Having inherited BRCA1 or BRCA2 gene
– Ways to prevent and detect breast cancer:
•
Monthly breast self-exams beginning at age 20
•
Mammograms every 1 to 2 years for women in their 40s
•
The drug tamoxifen can be used for breast cancer treatment as well as
protection.
•
Testicular cancer
– Rate had been increasing in young men, possibly because of exposure to
xenoestrogens.
– Fairly rare and can be cured if detected early
•
Prostate cancer
– Prostate cancer occurs primarily in men over age 65.
– Early diagnosis relies on two tests:
•
Finger rectal exam
•
Prostate-specific antigen test (PSA), which detects a protein in blood that
is associated with abnormal growth of the prostate gland
– This cancer develops very slowly.
•
Skin Cancer
– Melanoma is a malignant form of skin cancer.
– It is the 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 lifethreatening; the abnormal cells can be removed by:
•
Surgery
•
Scraping
•
Freezing
•
Burning
– Remember the “ABCD” rules when examining your skin for moles that could be
melanoma:
•
•
Asymmetry
•
Border
•
Color
•
Diameter
Colon Cancer
– Colon cancer affects men and women equally.
– It causes about 60,000 deaths annually in the United States.
– 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 show that diet is associated with cancer.
•
Certain dietary choices may help prevent cancer, such as increased consumption of B
vitamins, vitamin C, and folic acid.
•
Scientists speculate that the human body may not be capable of digesting modern-day
processed foods, leading to an accumulation of toxic chemicals that may cause cancer.
Cancer Treatments
•
There are three medical treatments for cancer:
– Surgery to remove the tumor
– Radiation therapy to destroy cancer cells
– Chemotherapy or the use of toxic chemicals (drugs) to kill cancer cells
•
Curing Childhood Cancers
– There are 20,000 new children cancer patients every year.
– 80% are cured and live to adulthood.
– Many have ongoing medical problems.

Experimental Cancer Therapies
– Medical researchers are looking for ways to enhance the body’s immune system
so that abnormal cells are eliminated and so that they do not compromise the
body’s immune system.
– Angiogenesis is when a tumor develops a network of new blood vessels to
support it with nutrients.
– Today, 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.
Cancer: Understanding Risks and Means of Prevention
•
What things are you doing that help decrease your risk of getting cancer?
•
What are you going to add to your life that will further help decrease your risk?
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.org
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)