Week 6 - Epidemiology Of Cancer

Question 1

Things to consider :

Answer 1

Person - who suffers and who Dosen’t

Place -does frequency cash from place to place

Time - does frequency change over time

Question 2

Cancer incidence

Answer 2

Number of new cases of cancer that occur during a specified time period in a defined population

Question 3

Cancer outcome

Answer 3

Mortality rates and number of deaths :standardised European and worldwide

Survival rates - overall and event free

Question 4

Prevalence

Answer 4

Measures the burden of disease in a population

Which is made up of all ongoing cases of disease

Important for health services planning

• further tests
• continued treatment e.g. Chronic myeloid leukaemia
• late effects of treatment I.e. Second cancers

Can be diffcult to quantify accurately

Question 5

Risk transition

Answer 5

As a country develops , the diseases that affect the population shift from primarily communicable diseases ( infectious ) to primarily non - communicable

This is due to

• improvements in medical care
• aging population
• public health interventions (vaccination, clean water )

Question 6

Childhood cancers

Answer 6

• Diagnosed <14 yrs
• Different from adult cancers - histopathologically and clinically
• comparatively responsive to therapy (> 85% with acute lymphoblastic leukaemia now survive > 5 yrs

Rare -
: < 1% of total malignancies
: 1,400 cases diagnosed in UK each year

Question 7

How can descriptive epidemiology help ?

Answer 7

Global differences in incidence patterns aid in identifying causes

Mortality : very high in developing countries ( causes )
: access to care
: late stage at presentation

Question 8

Causes of cancer

Answer 8

• infections ( HPV, H.pylori , EBV,HTLV-1 )
• radiation
• lifestyle (diet , obesity , alcohol , tobacco )
• occupational
• hormonal
• genetics

Question 9

Common infectious causes of cancers and their prevalence …

Answer 9

HPV- cervical cancer -360,000 cases worldwide

HepB virus - liver cancer - 230,000

EBV /HIV- non-hodgkins lymphoma -9,000

Human herpes virus 8/HIV - kaposi’s sarcoma -45,000

Human T cell leukaemia virus - leukaemia -3,000

HepC virus - liver cancer - 110,000

Helicobacter pylori - gastric carcinoma , gastric lymphoma - 350,000

Schistosomes - bladder cancer -10,000

Liver flukes - cholangiocarcinoma -1,000

Question 10

Diet and cancer

Answer 10

1- cancer 2- dietary risk factors 3- dietary protective factors 4- other risk factors

1- oral cavity, pharynx and oesophagus 2- alcohol , very hot drinks , obesity , salted fish
3- fruit and veg
4- smoking

1- stomach 2- salt and salt preserved foods 3- fruit and veg 4- infection by H.pylori

1- colorectal 2- obesity , red meat , processed meat 3- fruit and veg , plant foods rich in fibre 4- sedentary lifestyle

1- liver 2- alcohol 4- smoking

1- larynx 2- obesity after menopause , alcohol 4- reproduction and hormonal factors , sedentary lifestyle

1- endometrium 2- obesity 4- low parity , sedentary lifestyle

Question 11

Tobacco and cancer

Answer 11

Associated with 50% to 60% of all cancer deaths

Causally linked to cancers of the lung , upper respiratory tract , oesophagus , bladder and pancreas

Probably a cause of cancer of stomach , liver , kidneys , colon and rectum

Question 12

Predisposition Vs susceptibility

Answer 12

• certain rate gene mutations predispose an individual to specific diseases

These manifest as familial cancer syndromes

Each such predisposing mutation contributes only 0.1% or less of cancer incidence (total <5%)

Susceptibility genes are these genetic variants that make the individual more susceptible to certain types of cancer and may linked to specific exposures

Question 13

How can you control cancer ?

Answer 13

: prevention
- legal and lifestyle changes ; vaccines

: screening
- early detection and diagnosis

: disease management
- improving treatments and quality of life

Question 14

How does disease progression take place ?

Answer 14

Preclinical phase :

Exposure -> onset of disease (primary prevention to stop onset of disease)

Clinical phase :

Onset of disease (secondary prevention ) -> onset of symptoms and/or signs and arrested progression(tertiary prevention ) -> cure , control , disability , death

Question 15

Summary of prevention :

Answer 15

Prevention can be targeted at different points along disease pathway

Primary aims to reduce exposure

Secondary aims to identify those with pre-clinical disease to influence progression of disease

Tertiary aims to modify outcomes of disease

Assessment of impacts of prevention programme important

Knowing the population screened , observed or intervened with is very important