4. Epidemiology

epidemiology

study of disease incidence

• used to determine incidence of cancer in population for factors of:

  • age

  • gender

  • race

  • geographic location

• used to determine recent trends/distribution of disease

population studies

look for significant trends, unusual occurrences, future impact on resources, society as a whole

• helps drive screening process + treatment

• long-term process

incidence

# of new cancer cases diagnosed in given population during specific period of time

• usually expressed as # of cases/100,000 people per year

cancer incidence

• has declined annually since 2011

  • -1.5% for men

  • -1.2% for women

• vary depending on

  • exposure to risk factors

  • lifestyle + behaviours

  • early detection (screening) practices

probability

chance of developing cancer over defined period

= likelihood at birth that Canadians will develop cancer at some point in their lifetime

• reflects average experience of people in Canada

• expressed as percentage or as chance

  • eg. 20% or 1 in 5 people over a lifetime

prevalence

burden of disease in defined population at defined time

= probability that member of population has given condition at point in time

• increases w/ increased incidence + duration

• decreases w/ increased mortality + cure rates

• reflects both frequency of occurrence + prognosis for particular cancer

• can support informed decision making → ensure healthcare services meet needs of specific populations

mo

mortality

death rate

• usually expressed as # of deaths/100,000 per year

• includes

  • deaths of patients diagnosed in earlier years

  • persons w/ new diagnosis during year

• excludes

  • patients for whom diagnosis of cancer is made after death

• cancer mortality decreasing over time → improved treatment

net survival

estimate of # of people who are alive at some point after diagnosis, accounting for other causes of death

• usually 5-years

  • exception for brain primary = 1-year

  • dependent on stage at diagnosis

    • decreases w/ increased stage

• ie. if someone gets this cancer, will they survive in 5 years?

  • breast cancer described by 20-year survival rates

• vary depending on type of cancer

  • lung = 22%

  • colorectal = 67%

  • breast = 89%

  • prostate = 80%

osteosarcoma

• most common bone tumour in children

  • bone cells rapidly dividing during adolescence + puberty

chondrosarcoma

• common bone tumour in adults

• rare in children

multiple myeloma

malignancy of plasma cells

• mainly affects middle aged + older adults, peak in 60s

• more common in men than women

metastatic bone disease

• most often in spine + pelvis (away from trunk)

• most commonly from lung, prostate, breast, kidneys, thyroid

acute lymphocytic leukemia (ALL)

leukaemia most common in children

acute myeloid leukaemia (AML)

leukemia most common in older adults

chronic lymphocytic leukemia (CLL)

most common leukaemia in adults

thyroid

• most common endocrine tumour

  • but only 2% of cancers

pituitary tumours

• benign + usually asymptomatic

lung

most common cancer worldwide

head and neck

• incidence increase in oropharynx due to HPV

• nasopharynx cancer most common in HK, southern China, SEA

• oral cavity + BOT common in India due to chewing betel nuts

CNS

• accounts for 1.4% of all malignancies

• considered rare

pancreas

4th most deadly cancer in US

• high mortality rate → one of most deadly cancers

• centrally located in abdomen

  • symptoms misattributed to other problems/organs → misdiagnosis

  • difficult to focus treatment on small organ

cervix

3rd most common malignancy in women worldwide

prostate

most common cancer in males

breast

most common non-cutaneous malignancy in US

• largely affects women

skin

non-melanoma skin cancers = most common form of malignancy in humans

• higher than any other type of cancer combined

  • often don’t metastasize + are slow-growing → easy to treat

malignant melanoma = deadliest form of cancer on annual basis