(5) Cancer – Flashcards
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Incidence rate
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406/100,000 Canadians
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Most Common type of cancer?
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Non-melanoma skin cancer
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Cancer is the..
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leading cause of death in Canada (30% of all mortality - 2004). Primarily a disease of older people. Leading cause of potential years of life lost (age of death-life expectancy). *The use of tobacco was the most important cause. PYLL higher for women, because PYLL is higher for breast cancer than prostate cancer.
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How Cancer Works
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Uncontrolled multiplication of cells. Normal cells have a biological clock, programmed to reproduce a certain # of times or for a certain period and then die. Cancer occurs when mutations happen to DNA, cause the mechanisms of normal cell growth to malfunction, which allows uncontrolled cell division. The cell doesn't die like it should, it goes on making new cells that the body doesn't need. Cancer uses the bodies energy/nutrients intended for healthy cells.
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How does a cell become a cancer cell?
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Exposure to carcinogens (tar, asbestos, certain chemicals, ultraviolet light causes DNA damage that leads to uncontrolled growth and division that can form tumours. Grows out of control and invades other tissues. Many are killed by white blood cells, which are apart of the immune system.
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Tumours
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Cancer cells that are not killed by white blood cells can progress and accumulate in clumps called tumours. This often happens. Non cancerous tumours are called benign, they cannot invade other tissues, but can still put pressure on organs.
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Metastasis
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The process of cancer spreading. Malignant cells break away from the primary tumour, attaching to and degrading proteins that make up the surrounding extracellular matrix, (separates tumour from surrounding tissue) No matter where cancer spreads, it's always named for the place it started. Critical event is the growth of a new network of blood vessels which is called "tumour angiogenesis"
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Malignant Tumours
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tumours that metstasize, r spread from the site where it originated to another place in the body. Malignant cancer cells enter the lymph/blood vessels and metastasize.
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Carcinogens
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Cancer causing agents
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Pathogens that cause Cancer
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Some types of HPV and Hep B.
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Cancers of the immune system
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Make the body more vulnerable to potentially fatal infections
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When cancer is considered "cured"
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If the patient is still living 5 years after the diagnosis, which is an arbitrary figure. Survival rate is relative to the general population who is similar in age, race and gender.
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metastasis suppressors
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Body has a lot of these, they are a class of proteins.
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Primary prevention of Cancer
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Preventing a disease from occurring. (reducing exposure to carcinogens)
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Secondary prevention of Cancer
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Early detection and treatment of a disease. (early detection)
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Difficulty with Cancer
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Long latent period, difficult to establish cause/effect
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Lung Cancer
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Mortality rates have increased for females, and are even higher than for breast cancer. Asbestos + Cigarette smoking have a multiplicative effect on lung cancer risk. Early signs/ symptoms have not been very specific, which creates a difficulty for effective screening. • Leading mortal cancer • Smoking is the leading risk factor; followed by second hand smoke, asbestos, pollution • 5-year survival rate less than 20% - No effective screening - Typically caught too late
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Cigarettes
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Related to 27% of lung-cancer deaths, @ age of less than 70 years old 63% of death related to smoking. The most carcinogenic substances in tobacco are in the tar.
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Breast Cancer
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The most common non-skin cancer in females and the second leading cause of female cancer mortality in Canada.
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Risk factors for Breast Cancer
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female sex, older age, family history, alcohol use, estrogen promotes breast tumour growth (doesn't cause the mutations of cells), early menstruation (U12), late menopause, never having children, long-time usage of birth control pills, increase in mortality because implants impair early tumour detection. Diet may play a role.
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Tamoxifen
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drug that blocks the production of estrogen in breast tissue, reduces risk/occurrence/ recurrence of breast cancer, increases risk of urinary cancer.
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Reducing risk of breast cancer
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regular physical activity, tamoxifen, and mammography.
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Mammography
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Imaging technique for the breast that uses a low-dose x-ray
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conventional mammography
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stores the image directly on film
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digital mammography
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stores image of breast as a computer file
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Screening
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comprised of general examinations (e.g. mammography) done on apparently healthy populations to identify those who may potentially have the disease. should always be low-cost, non-invasive and low-risk. There will always be false positive results, 1000 screenings, 100 positives, and 4 actually have breast cancer.
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Testing
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done on those who are believed to have cancer. It is comprised of more specific tests (e.g. biopsies/microscopic examinations) to more thoroughly identify the presence. More expensive, time-consuming, invasive and risky. Purpose of separating false positives from actually diseased people. *Not reasonable to test an entire population.
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Biopsy
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involves removal of tissue that is suspected to be cancerous for further examination
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Is self-exam recommended?
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No, because the costs outweigh the benefits. False positives outweigh true positives and cause extra worry and concern and unnecessary biopsies.
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Prostate Cancer
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The most common non-skin cancer in men. (2nd most common for M) It is the 3rd leading cause of male cancer mortality. Men may have no symptoms, or less rigid erections, decrease in ejaculation, blood in urine, severe pain in back, hips and thighs. It can be detected through a digital rectal exam. If detected early, 95% survival rate.
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Prostate Gland
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a walnut sized gland near the bladder that is only in males.
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Prostate-specific antigen test
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measures blood levels of the protein, elevated levels may indicate prostate cancer, but it could also be a false positive. Way to test to see if you have prostate cancer
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Treatment for prostate cancer
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surgically remove the gland, implant radioactive seeds to kill the cancerous cells, or cryotherapy (freezing of the gland), or drugs to decrease male hormone levels.
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Colorectal Cancer
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Symptoms include a change in bowel movements lasting over 10 days, pain/tenderness in the abdomen, blood in stool. 2nd leading cause of cancer mortality in Canadians overall.
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First stage of Colorectal Cancer
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non-cancerous growths called polyps which are small mushrooms inside the intestine. Not malignant, but the abnormal cancerous cells are within the polyp, and can be removed.
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Advanced stage of Colorectal Cancer
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Cancer cells invade the nearby colon tissue growing into and beyond the walls of the colon/rectum, and then the tumour sheds cells into the circulatory system which spreads cancer to other organs
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Risk factors for colorectal cancer
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older age, male, inflamatory bowel disease, hereditary factors, family history of it, lack of physical activity, sedentariness. Unhealthy diet w/ low fibre.
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Cervical Cancer
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Leading RF is infection with high-risk types of HPV.
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Colon
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apart of the large intestine
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Rectum
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Final par of the colon, just before it exits the body thru the anus.
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Cervix
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outer portion of the uterus where it meets the vagina
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Risk factors for Cervical cancer
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HPV, fam history, weakened immune system, chlamydia, long-term use of birth control pills, 3+ full-term pregnancies, pregnancy U17.
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Pap test
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A cervical smear that can detect abnormal changes in cells on the surface of the cervix. Mild abnormalities may revert back to normal or may proceed to more advanced stages of cervical cancer. Recommended to get them after age 21 or 3 years after first sexual contact. They reduce morality, morbidity among women aged 30-69. Under the age of 25 the benefits are outweighed by the harms of this screening.
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Basal Cell Carcinoma
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Most common form of skin cancer, highly treatable. 1/1000 people die from it, it almost never spreads and the lesions grow very slowly. It looks like a pearly white/waxy/light-pink, flesh-coloured/ brown bump.
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Malignant Melanoma
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Most dangerous form of skin cancer, five year mortality rate, incidence and mortality rate are rising in Canada. Because of increased exposure to solar radiation.
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ABCDE
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Asymmetry, Border (irregular), Colour (white, blue, red), Diameter (larger than 6mm), Evolving (wet, itches, forms scab/crust)
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Treating Cancer
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Huge thing is when it is discovered, early vs later. Surgical removal reduces the possibility of mestastic transfer. Radiation therapy- radiation kills cancer cells by damaging the DNA. Chemotherapy kills the cells that divide rapidly and it also kills normal cells. Molecular targeted therapy interferes with specific molecules on cancer that are different than normal cells. Hormone therapy when its hormones that help cancer grow.
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Immunotherapy
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suppressor cells, that interfere with the activation and proliferation of another type of immmune system cell (T-Cell) attack tumours.
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Photodynamic therapy
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makes cells sensitive to light, then practitioner shines laser beam at the tumour, killing sensitized cells.
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Gene Therapy
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Uses genetic material to modify cells tumour suppressor genes to rapidly dividing cells to slow/stop tumour growth. It's less toxic than chemotherapy.
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Preventing cancer
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1/2 of cancers can be prevented, 80% of all cancers are environment. Primary prevention: dont use tobacco products, decrease exposure to ultraviolet light, minimize exposure to x-rays, minimize exposure to carcinogens, reduce amount of fat you eat, don't eat mouldy peanuts, get beta-carotene and vitamins, watch your weight. don't drink alcohol, do checkups/self-exams.
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Normal Cells
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Divides only under the right conditions. "Cell cycle" controlled by proteins that perform checks before division occurs
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Types of Cancer
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• Lung (# 1 mortality) • Skin (# 1 incidence) • Breast (#2 F) • Prostate (#2 M) • Colon and Rectal (# 3) • Cervical (video) • Ovarian Lifetime probability of getting cancer= 45% M an 42% F.
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Risk Factors for Skin Cancer
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• Fair skin, light eyes, fair hair • A tendency to develop freckles and burn instead of tan • A history of childhood sunburn or intermittent, intense sun exposure • A personal or family history of melanoma • A large number of nevi, or moles (200+; 50+ if under age 20) or atypical moles
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Breast Cancer survival rate and caution
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• Most common cancer in females • If caught early, survival rate 80%+ • Most dangerous when it spreads to other tissues, forming secondary tumours. • There are lymph nodes close to the breast • Once cancer cells reach lymph nodes, they can potentially spread t
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Reducing Cancer Risk
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Don't smoke, avoid second-hand smoke • Reduce exposure to carcinogens - e.g., UV light, radiation, asbestos, acrylamide • Cancer-smart nutrition - ↑ antioxidant-rich fruits & vegetables (e.g., vitamin C, D, folate); reduce fat, BBQed foods • Receive available vaccinations (e.g. HPV) • Get a good night sleep (Deprivation ↑ cancer risk) • Early detection through screenings
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Take Home Messages
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• Cancer accounts for 30% of all deaths • Cancer occurs more frequently in older age • Lung, breast, colorectal and prostate account for over half of all newly diagnosed cancers • Mortality rates dropped between1998-2007 - Improvements in screening, early detection - More effective, less toxic treatments • Non-malignant melanoma most commonly diagnosed cancer
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Metastasis
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The spread of the disease from the place it originated to another place in the body
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Multi-Stage Screening
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A technique that is applied to apparently healthy population. Starts with simple, inexpensive, less-invasive tests. People with positive results are given further screening, more expensive/sophisticated/invasive tests.
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Potential years of life lost
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A number = to life expectancy minus age at death.
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Latent period
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the incubation period for disease. The period between initial exposure to the disease causing agent and the development of signs/symptoms of the disease.
