Transcript Chapter 13

Chapter 13
Cancer:Understanding Risks
and Means of Prevention
Incidence of Various Cancers
• Cancers of the stomach, uterus, cervix, and testis
and Hodgkin’s disease 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 is the rate of lung cancer in both
men and women caused by smoking.
What Is Cancer?
• Cancer is 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
reproduces 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 referred to
as a benign tumor.
What Is Cancer?
• 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 successfully, the
tumor will not regrow.
• Malignant tumors are composed of cells that grow
rapidly, have abnormal properties, and invade
normal cells.
• Malignant cells have altered shapes.
What Is Cancer?
• A pathologist (a physician who specializes in 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.
What Is Cancer?
• Cancers are medically classified according to the
organ or tissue in which the tumor originates.
• There are four major categories:
– Carcinomas (e.g., cancer 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)
What is Cancer?
What Is Cancer?
• Fifty percent of all human cancers originate
in one of four organs:
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Lungs
Breast
Prostate
Colon
Cancer Development
Cancer Development (Four Stages)
• 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
• Scientific research indicates that 90% to
95% of all cancers (including breast, lung,
stomach, colon, skin, and prostate cancers)
are not inherited from parents (except in a
few families).
• It is estimated that only 5–10% of all
cancers are hereditary.
Environmental Factors
• 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.
Environmental Factors
• Three classes of environmental agents:
– Ionizing radiation
– Tumor viruses
– Chemical carcinogens
• Ionizing radiation consists of x-rays, UV
light, and radioactivity, which damage cells
and chromosomes.
Environmental Factors
Tumor Viruses
• Four tumor viruses have been 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 that can interact
with cells to initiate cancer:
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Cigarette smoke
Pesticides
Asbestos
Heavy metals
Benzene
Nitrosamines
Xenoestrogens
• Chemicals found in the environment that
mimic the body’s estrogen hormone and
may cause breast cancer.
• Substances that contain xenoestrogens:
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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 does.
• Lung cancer could almost be completely
prevented 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
Common Cancers—Breast Cancer
• 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.
Dietary Fat and Breast Cancer
Common Cancers—Breast Cancer
© Photodisc
Common Cancers—Breast Cancer
• 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.
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 test (PSA), which
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.
• It is the fifth most frequently diagnosed
cancer among Americans.
• Exposure to sunlight is the primary cause of
all forms of skin cancer.
Common Cancers—Skin Cancer
• Basal cell carcinoma and squamous cell
carcinoma are usually not life-threatening;
the abnormal cells can be removed by:
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Surgery
Scraping
Freezing
Burning
Common Cancers—Skin Cancer
• Remember the “ABCD” rules when
examining your skin for moles that could be
melanoma:
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Asymmetry
Border
Color
Diameter
Common Cancers—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 vitamin C.
• 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
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.