Transcript Unit # 6: Cancer

Unit # 6: Cancer
Overview
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2nd leading cause of death in Canada.
29% of all mortality in 2000
Higher risk in people over 65, males
Leading cause of Potential Years of Life Lost
(PYLL)
– Ex. PYLL
• A man who has a life expectancy of 70 dies at age 65
from cancer, his PYLL = 70-65 = 5
Deaths and ASMR for all cancers
ASMR= age
standardized mortality
rate
Mechanism of cancer
• Normal, healthy cells have genes which control:
• When they divide
• When they stop dividing
• When they die
• Repetitive exposure to certain agents can cause
an accumulation of mutations in these genes, and
they lose this control
• Cancer is a disease evidenced by:
uncontrolled cell growth
Mechanism of cancer
The mutations that result in cancer
are caused by:
Carcinogens: cancer causing agent
– Tobacco Smoke
– Radiation: UV, X-Ray
– Pathogens: Human Pappiloma Virus,
Hepatitis B
– Benzene
– Asbestos
Development of Cancer
Main Genes Responsible for Cancer
• Proto-oncogens/oncogenes
• Proto-oncogenes regulate
–how often a cell divides
–how specialized it is (able to perform a
particular task)
• A mutation turns proto-oncogenes into oncogenes
and the cell no longer has regulated control over
division
Main Genes Responsible for Cancer
• Tumour Suppressor Genes
– normally function to suppress cancerous growth
by:
• Suppressing uncontrolled growth
• Repairing DNA mutations
• Telling the cell when to die
– Mutations can turn these genes off
Tumour characteristics
• Benign tumours are growths which are enclosed
in a membrane
• Still have control over growth
• Do not invade
• Do not metastasize (spread)
• Malignant tumours are cancerous growths which
are not enclosed in a membrane
• No control over cellular growth
• Invade
• metastasize
Benign vs. Malignant tumor
Cancer Summary
Cancer Staging
• Overall Stage Grouping
– Stage 0: a growth that stays in place, no metastasis,
no invasion
– Stage 1: cancer localized to one area
– Stage 2: cancer is localized to one area, but is more
aggressive
– Stage 3: invasion into local areas and/or lymph nodes
– Stage 4: Metastatic cancer
Prostate Cancer
Survival Rate
• Cancer is considered cured if patient lives five
years after original diagnosis
– Varies with the type of cancer.
• Ex. High with skin cancer, low with brain cancer
• Survival rate increases with EARLY DETECTION!
• However, cancer can have a very long latent
period
– latent period = time between first exposure to a
carcinogen (ex. Cigarette smoke) and the first signs
and symptoms showing (ex. Lung cancer)
Cancer Treatment in General
• Surgery
• Radiation
• Chemotherapy (drugs)
MAJOR TYPES OF CANCER
Female Age-standardized mortality
rates for selected cancers
Male Age-standardized mortality rates
for selected cancers
Lung Cancer
• Highest mortality rate of any cancer
• Rates are actually increasing in Canadian
females 
Lung Cancer Risk Factors
• Smoking is the leading risk factor
– Smokers are 10-20 times more likely to get lung
cancer than non-smoking population
– Cigarette tar is the most carcinogenic
– Asbestos can also cause lung cancer
• Previously used to insulate schools, hospitals, buildings
• Risk increases substantially when patient is
exposed to both carcinogens
• No effective screening for lung cancer in place
Smoking and Lung Cancer
Globe and Mail, Sept 29, 2009
“Ontario says tobacco use costs the province
$1.6-billion a year for health care and causes
about 13,000 deaths annually. It said smoking
is the province's No. 1 cause of illness and
premature death”
Breast Cancer
• 2nd most common cancer worldwide
• 5th mortal cancer
Female Age-standardized incidence rates for breast cancer
Female Age-standardized mortality rates for breast cancer
What does this suggest??????
Risk factors for breast cancer
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Females are at much higher risk (obviously!)
Older Age
Family history
Early menstruation and late menopause: since
estrogen is known to promote breast tumour
growth
• Pregnancy: if first pregnancy occurs after age 30
• Diet: dietary fat? Alcohol?
• Physical Inactivity
Preventing breast cancer
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Mostly secondary prevention measures
Breast self-examination
Mammography a low dose breast X-ray
Multi-stage screening:
– Involves an initial general screening test, then
subsequent diagnostic tests become more and more
specific
– Note: screening is done on healthy populations,
testing is done on people who already have the
disease
Multi-level screening
Prostate Cancer
Prostate cancer
• Risk factors include the male gender, family
history and older age
• Often no symptoms are evident. However less
rigid erections, decreased ejaculated fluid,
blood in the urine or semen and severe back,
pelvis, hip or thigh pain may be evidenced
Prostate age-standardized incidence rates
Prostate cancer detection
• Digital rectal exam: Recommended for all
Canadian men over age 50
• Prostate specific antigen (PSA): paid for by the
Canadian government for males over 50
Prostate Cancer Treatment
• Surgical removal of the gland
• Small radioactive material can be implanted to
kill cancerous cells
• Cryotherapy: freezing the prostate
• Drugs: to decrease male hormone levels
Colorectal Cancer
• Third leading cause of cancer mortality in
Canadian males and females
• Higher in populations with poor diets
– High meat, high-fat, high-protein, low-fibre, lowcalcium
• Begins with the appearance of adenomatous
polyps (polyps = non-cancerous growths)
• These polyps can become cancerous and the
disease progresses accordingly
Colorectal Cancer
Colorectal Cancer
• Symptoms include:
– bowel movement change lasting more than 10 days
– Pain and tenderness in the abdomen
– Blood in the stool
• Risk factors include:
– Older age
– Male gender
– Inflammatory bowel disease
– Hereditary factors
– Family history
– Physical Inactivity
Cervical Cancer
Cervical Cancer
• Affects only females
• Can be detected early with the Pap test
• Risk factors include:
– early age of sexual intercourse
– multiple sex partners
– history of STDs
– tobacco use
Skin Cancer
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Most commonly diagnosed cancer
Easy to treat since it’s on the surface
It rarely metastasizes
Basal cell carcinoma= most common, easier to
treat
• Malignant melanoma= more aggressive,
metastasizes
How to Spot Skin Cancer:
ABCD
Skin Cancer Risk Factors
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Tobacco Smoke
UV exposure
Chronic non-healing wounds
Genetic predisposition
HPV infection
Age
Prevention of Cancer
• Primary prevention aimed at reducing risk
factors is useful. However, the cause of cancer
is often unknown
– Don’t smoke!
– Reduce UV exposure
– Minimize X-ray exposure
– Reduce fat intake
Prevention of Cancer
• Increase fibre consumption
• Get adequate amounts of beta-carotene
(Vitamin A precursor) and Vitamin C
• Reduce consumption of smoked, barbecued and
salted foods
• Keep a healthy weight
• Sleep at night; avoid night time shift work
• Avoid nitrites
• Clean with vinegar, avoid detergents