Transcript Cancer
Chapter 16 Cancer Leading cause of disease-related death among people under age 75 Second leading cause of death Evidence supports that most cancers could be prevented by simple lifestyle changes Tobacco is responsible for about 30% of all cancer deaths Poor diet and exercise habits account for another 30% of cancer deaths 2 Figure 16.1 Percentage of all cancer deaths linked to risk factors 3 What is Cancer? Definition: An abnormal and uncontrolled growth of cells that can lead to death Tumor: A mass of tissue that serves no physiological purpose Benign tumor: Mass of cells enclosed in a membrane that prevents their penetration of other tissues Malignant tumor: Can invade surrounding tissues Every case of cancer begins as: a genetic change in a cell that allows it to grow and divide when it should not 4 Figure 16.2 Tumor development occurs in stages 5 Metastasis Definition: The spread of cancer cells from one part of the body to another Primary tumor: original location of cancer Secondary tumors: New tumors 6 Stage Description 0 Early cancer, present only where it originated I More extensive II Greater tumor size III Cancer has spread to nearby lymph nodes/adjacent organs IV Advanced cancer; spread to other organs Types of Cancer Classified according to types of cells that give rise to them Carcinomas – arise from epithelial tissue Ex., skin Sarcomas – arise from connective tissue Bone, cartilage, etc. Lymphomas- arise from lymph nodes Leukemias - Cancer of the blood-forming cells in bone marrow. 8 The Incidence of Cancer American Cancer Society Estimates: 90% of skin cancer could have been prevented by protecting the skin from the sun 87% of lung cancer could have been prevented by avoiding exposure to tobacco smoke Regular screening and self-examinations could save an additional 100,000 lives per year 9 Lung Cancer Leading cancer killer in the U.S. ~158,000 deaths/year Risk factors Tobacco smoke (including ETS) contributes to 90% of lung cancer deaths Detection Difficult to detect early Symptoms do not appear until invasive stage Symptoms: Persistent cough, chest pain, or recurring bronchitis Diagnosis: CT scan (earlier?), chest x-ray or sputum examination, bronchoscopy 10 Lung Cancer Treatment If caught early, localized cancers can be treated with surgery Only 15% detected prior to spreading so, Radiation and chemotherapy are used in addition to surgery Overall, the 5-year survival rate is only 16% 11 Colon and Rectal (Colorectal) Cancer Risk factors Age (91% of cases occur in people 50 or older) Heredity, genetic propensity to develop polyps Diet, smoking, excessive alcohol use and obesity 12 Colon and Rectal Cancer Detection and treatment Regular screening tests are recommended beginning at age 50 Symptoms: bleeding from rectum and changes in bowel habits Treatment Primarily Surgery Radiation be used and chemotherapy can Breast Cancer Most common cancer in women Causes almost as many deaths in women as lung cancer Risk factors Strong genetic factor: Age: Most common in women over 50 Early onset of menstruation First child after 30 Current use of HT Unhealthy diet and lifestyle 14 Breast Cancer Early detection ACS recommends 1 mammogram/year (women over 40) Clinical and Self breast exams (starting at age 20) Symptoms may include a lump, changes in size, dimpled, redness or scaliness of nipple or breasts, Treatment Ultrasonography and biopsy to determine if cancerous If the tumor is discovered before it has spread, patient has 89% chance of surviving more than 5 yrs. 15 16 Prostate Cancer Most common cancer in men Risk factors Age( more than 60% of cases diagnosed in men over 65) Genetic predisposition Diet and Lifestyle African American and Jamaican men have highest rates in the world 17 Prostate Cancer Detection Blood test: Prostate-specific antigen (PSA) Rectal exam: Symptoms may include changes in urinary frequency, weak/interrupted urine flow, painful urination and blood in urine Treatment Surgical removal of the prostate and radiation (depends on stage and age) Radioactive seeds 5-year survival rate is nearly 100% 18 Cancers of the Female Reproductive Tract Cervical cancer Most cases stem from human papillomavirus (HPV) infection (STD) Prevention The PAP test is a highly effective screening test for this cancer All sexually active women ages 18-65 should be tested regularly Gardasil 19 Skin Cancer Types of skin cancer Basal cell carcinomas Squamous cell carcinomas Melanoma (most serious type) Most common form of cancer 1 million cases per year (68,000 are melanoma) Risk factors Excessive exposure to UV rays Common causes are sunburns and suntans Caucasians are 10X more likely than African Americans to develop basal and squamous cell carcinoma 20 Skin Cancer Prevention Avoid long term overexposure to sunlight Detection Melanoma ABCD test of screen The Causes of Cancer The role of DNA (Deoxyribonucleic acid) Each human cell has 23 pairs of chromosomes Gene: Smaller unit of DNA DNA mutations and cancer Mutagens: Radiation, certain viruses and chemical substances Oncogenes: A gene in which mutations are associated with the transformation of a normal cell into a cancer cell Tumor suppressor gene: Type of oncogene that normally restricts cellular growth Hereditary cancer risks If a hereditary cancer, abnormal gene is present in sperm/egg If not hereditary, a mutation has occurred Most inherited cases of breast cancer are associated with mutated BRCA1/2 gene (breast cancer gene 1 and 2) 22 The Causes of Cancer Cancer promoters Definition: Do not directly produce mutations, they instead accelerate the growth of cells without damaging or permanently altering the DNA Estrogen is an example 23 Dietary Factors Food choices affect your cancer risk by: exposing you to potentially dangerous compounds and depriving you of protective compounds Dietary fat and meat Diets high in “bad” fats and meat may contribute to colon, stomach, and prostate cancers Omega-3 fats are healthier for body Alcohol Risk of oral and colon cancer Fried foods Not enough Fiber Not enough Fruits and vegetables Phytochemicals Inactivity and obesity 24 Carcinogens in the Environment Microbes About 15% of the world’s cancers are caused by microbes Ingested chemicals Nitrosamines: Nitrates and nitrites found in processed meats that combine with dietary substances and become highly potent carcinogens Environmental and industrial pollution Radiation 25 Figure 16.8 The seven major warning signs of cancer 26 Preventing Cancer Lifestyle choices Avoid tobacco Control diet and weight Regular exercise Protect skin from the sun Avoiding environmental and occupational carcinogens Follow recommendations for cancer screenings 27