Chapter 12

Chapter 12Cancer

Prevention

CHAPTEROUTLINE Cancer Develo

pmentIncidence of Cancer

Guidelines for Preventing Cancer

Warning Signals of Cancer

Recommended Checkups

Key TermsCancer: Group of diseases characterized by uncontrolled growth and spread of abnormal cellsBenign: NoncancerousMalignant: Cancerous

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Key TermsDeoxyribonucleic acid (DNA): Genetic substance of which genes are made; molecule that contains cell’s genetic codeRibonucleic acid (RNA): Genetic material that guides the formation of cell proteins

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Key TermsOncogenes: Genes that initiate cell divisionSuppressor genes: Genes that deactivate the process of cell division

Angiogenesis: Formation of blood capillariesMetastasis: The movement of cells from one part of the body to another

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Cancer DevelopmentMore than 100 types of cancer can develop in the body

The process of cancer begins with an alteration in DNAWithin DNA are oncogenes and tumor suppressor genes, which normally work together to repair and replace cellsDefects in these genes ultimately allow the cell to grow into a tumor; defects are caused by

External factors such as radiation, chemicals, and virusesInternal factors such as immune conditions, hormones, and genetic mutations

Cancer starts with the abnormal growth of one cell, which then can multiply into billions of cancerous cells

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Cancer DevelopmentA critical turning point in the development of cancer is when a tumor reaches about one million cellsAt this stage, it is referred to as carcinoma in situAn undetected tumor may go for months or years without any significant growthWhile encapsulated, it does not pose a serious threat to human healthTo grow, tumors require more oxygen and nutrients

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Cancer DevelopmentIn time, a few cancer cells start producing chemicals that enhance angiogenesis (capillary or blood vessel formation into the tumor)Angiogenesis is the precursor of metastasisThrough the new blood vessels formed by angiogenesis:

Cancerous cells break away from a malignant tumorThey migrate to other parts of the bodyThey can cause new cancers

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12.4How Cancer Starts and Spreads

Cancer DevelopmentOnce cancer cells metastasize, treatment becomes more difficultTherapy can kill most cancer cells, but a few cells might become resistant to treatmentTreatment-resistant cells can grow into a new tumor that will not respond to the same treatment

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Cancer StatisticsCancer is the second leading cause of death in the U.S.About 23% of all yearly deaths are caused by cancerAproximately 1 in 2 men and 1 in 3 women in the U.S. will develop cancerMore than 560,000 Americans die from cancer each yearMore than 1.3 million new cases are diagnosed each year

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12.5Death Rates for Major Cancer Sites

Critical ThinkingHave you ever had or do you now have any family members with cancer?Can you identify lifestyle or environmental factors as possible contributors to the disease?If not, are you concerned about your genetic predisposition, and are you making lifestyle changes to decrease your risk?

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Cancer-Causing FactorsAs much as 80% of all human cancer is related to lifestyle or environmental factors

Diet ObesityTobacco useSedentary lifestyleExcessive use of alcoholExposure to occupational hazards

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12.7Cancer-Causing Factors

SOURCE: Harvard Center for Cancer Prevention. Causes of Human Cancer, HarvardReport on Cancer Prevention, 1 (1996).

Guidelines forPreventing Cancer

Get proper nutritionAbstain from tobaccoAvoid excessive sun exposureMonitor estrogen, radiation exposure, and potential occupational hazardsEngage in physical activityMaintain recommended body weight

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Dietary GuidelinesPredominately a vegetarian diet (high in fiber and low in fat)Should include a variety of fruits and vegetables, in particular cruciferous vegetablesThe use of tea, soy products, calcium, and omega-3 fats is encouragedAdequate fiber intake is recommended (25 to 38 gr/day)Protein intake should be kept within the recommended guidelinesAvoid salt-cured, smoked, and nitrite-cured foods (nitrite and nitrates are used to prevent the growth of harmful bacteria in processed meats but lead to the formation of nitrosamines, which cause stomach and esophageal cancers)

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Dietary GuidelinesAlcohol, if used at all, should be consumed in moderation, 1 (women) to 2 (men) servings per dayGrilling of meats at high temperatures is discouragedConsume ample amounts of fruits and vegetables which are high in antioxidants and phytochemicals

Antioxidants seem toAbsorb free radicals before they can cause damageInterrupt the sequence of reactions once damage has begun

Phytochemicals (plant chemicals) seem to prevent cancer by blocking the formation of cancerous tumors and disrupting the process at almost every step of the way

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Lowering Cancer Risks

Abstain from Tobacco UseThe biggest carcinogenic exposure in the workplace is cigarette smokeOf all cancers, at least 30% are tied to smoking, and 87% of lung cancers are linked to smokingUse of smokeless tobacco increases the risk for mouth, larynx, throat, and esophageal cancers

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Avoiding Excessive SunExcessive exposure to ultraviolet radiation (both UVB and UVA rays) contributes to skin cancer1 in every 6 Americans will develop some type of skin cancerThe most common sites of skin cancer are those areas exposed to the sun most often (face, neck, and back of the hands) Nearly 90% of the almost 1 million yearly cases of basal cell or squamous cell skin cancers in the U.S. could be prevented by protecting the skin from the sunMelanoma is the most deadly form of skin cancer, causing 7,600 yearly deaths

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Avoiding Excessive SunTanning of the skin is the body’s natural reaction to permanent damage from too much sunEven small doses of sunlight add up to a greater risk for skin cancer and premature agingAvoid sun exposure between 10:00 am and 4:00 pmSun lamps and tanning parlors provide mainly ultraviolet A rays (UVA) and have been linked to melanoma

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Avoiding Excessive SunApply sunscreen lotion about 30 minutes before lengthy exposure to the sunA sun protection factor (SPF) of at least 15 is recommendedWhen swimming or sweating, reapply waterproof sunscreens often (sunscreens lose strength when diluted)

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Critical ThinkingWhat significance does a “healthy tan” have in your social life?Are you a “sun-worshiper,” or are you concerned about skin damage, premature aging, and potential skin cancer in your future?

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Monitoring Estrogen, Radiation Exposure, & Potential Occupational Hazards

Use of estrogen therapy has been linked to endometrial cancer in some studiesExposure to radiation increases the risk for cancer(use the lowest dose possible to keep cancer risk down)Occupational hazards increase the risk for cancer

Examples include asbestos fibers, nickel and uranium dusts, chromium compounds, vinyl chloride, and bischlormethyl ether

Cigarette smoking magnifies the risk from occupational hazards

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Maintain Physical ActivityAn active lifestyle seems to have a protective effect against cancerCancer mortality in active men and women is lowerA daily 30-minute moderate-intensity exercise program lowers the risk for colon cancer and may lower the risk for cancers of the breast and reproductive system

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11.9Association between Physical Fitness and Cancer Mortality

Cancer PromotersPhysical inactivityBeing more than 10 pounds overweightFrequent consumption of red meatA diet high in fatCharred/burned foodsFrequent consumption of nitrate/nitrite-cured, salt-cured, or smoked foods

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Cancer PromotersAlcohol consumptionExcessive sun exposureEstrogensMethyleugenol (flavoring agent in packaged foods)RadonWood dust (high levels)

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Warning Signals of CancerChange in bowel or bladder habitsSore that does not healUnusual bleeding or dischargeThickening or lump in breast or elsewhereIndigestion or difficulty in swallowingObvious change in wart or moleNagging cough or hoarseness

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Recommended CheckupsInclude health counselingDepending on age and gender, may include examinations for

cancers of the thyroid, oral cavity, skin, lymph nodes, testes, and ovariessome nonmalignant diseases

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Recommended CheckupsBreast checkup

Women 40 and older shouldHave an annual mammogramHave an annual clinical breast examination (CBE) Optional breast self-examination (BSE)

Women 20–39 should Have a clinical breast examination every 3 yearsOptional BSE

Women at increased risk (family or personal history) should discuss frequency and additional testing with their doctors

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Recommended CheckupsColon & rectum checkup

Beginning at age 50 follow one of the examination schedules below:

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every yearFlexible sigmoidoscopy (FSIG) every 5 yearsFOBT or FIT every year and FSIG every 5 yearsDouble-contrast barium enema every 5 yearsColonoscopy every 10 years

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Guidelines for Preventing

Cancer

Warning Signals of

Cancer


Recommended CheckupsProstate checkup

Beginning at age 50, men with life expectancy of at least 10 years should have the choice of having these tests annually

A prostate-specific antigen (PSA) test A digital rectal exam

Men at high risk (African-American and strong family history) should begin testing at age 45

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Cancer

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Recommended CheckupsUterus checkup

Cervix: Three years after beginning of vaginal intercourse, but no later than 21, women should have a Pap test each year or a liquid-based test (less frequent after the age of 30 and following three consecutive tests with normal findings)Endometrium:

At menopause all women should be informed about risks and symptoms and report unexpected bleeding or spotting to their doctorsBeginning at age 35, women with or at risk for hereditary nonpolyposis colon cancer should be offered an endometrial biopsy annually

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Cancer

Warning Signals of

Cancer


End of Chapter

Chapter 12

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