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Unformatted text preview: PA and Cancer Chapter 11 Cancer : family of related diseases that result from uncontrolled growth and spread of abnormal cells, which usually become a tumor Magnitude of the Problem: USA Leading cause of morbidity and mortality in developed nations About half of men and a third of women in the US will develop some form of cancer during their lifetimes Deaths: rose in 1980’s; plateau in 1990’s 2003: ~556,000 deaths 2 nd compared to CVD Lung cancer history vs. others Since the 1930s, the death rates from most cancers have stayed about the same or decreased Only lung cancer has increased steadily 1/3 due to nutrition & PA New cases: 200,000 more expected in 2003 vs. 1992 $170 billion total annually 15% genetic - therefore, key public health issue Primary & secondary prevention Same in Canada except where noted Most common - incidence (new cases) Women: breast Men: prostate Most deadly (men & women): lung Colon & rectum cancer: 3rd in new cases & deaths Canada: 2nd in deaths in men Etiology Uncontrolled reproduction & spread of abnormal existing cells Cell division to replace or repair cells in some types of tissue # of cycles controlled by telomere = cell life span Telomeres shrink each time the cell divides until they reach a critical length that inhibits further division 80-90% of cancer cells produce telomerase, inhibiting normal clipping of telomere and promoting uncontrolled division Normal function requires tumor suppressor genes 1st phase: Initiation Mutation factors (carcinogens) damage normal cells into potentially harmful cells • E.g., radiation, chemicals, viruses • DNA mutations may: activate oncogenes (genes that promote cell division) inactivate tumor suppressor genes (genes that slow down cell division or cause cells to die at the right time) 2nd phase: Promotion Tumor growth by other agents • Including normal endogenous hormones Become malignant (cancerous) • Invade surrounding tissue or metastasize • Metastasize migrate through the blood or lymph systems to other body tissues, where they build colony tumors at a new site and continue growing Naming/Categorizing Cancers vary in their rates of growth, patterns of spread, and responses to different types of treatment Benign tumors: don’t metastasize and seldom kill people; noncancerous Named by site of origin Carcinoma: from epithelial cells Sarcoma: connective tissue 4 general stages (further type-specific definitions available) I: small, localized, usually curable II & III: advanced, localized or have spread to local lymph nodes IV: usually inoperable or metastasized Low daily doses of radiation can shrink tumors but the wrong dose of radiation can also cause cancer growth Viruses are also believed to contribute to cancer Inject new DNA sequences into cells Ex: chronic hepatitis B infection can turn into liver cancer...
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This note was uploaded on 08/13/2008 for the course EDKP 330 taught by Professor Koziris during the Fall '07 term at McGill.
- Fall '07