Oncology Lecture 1
Cancer Epidemiology – Dr. Alina Vrieling
A lot is involved when it comes to the
oncological patient. Things such as
immunotherapy, systemic therapy,
pathology, chemical carcinogens,
genetics, but also epidemiology.
Cancer epidemiology refers to both
the etiology (the cause of a disease or
the science that deals with such
causes) and the cancer itself.
In this lecture, we shall talk about descriptive cancer epidemiology, etiologic cancer
epidemiology (risk factors) and cancer epidemiology in Nijmegen.
Descriptive Cancer Epidemiology
The lifetime risk of cancer in females is 38% (>1/3) and the lifetime risk of cancer in
males is 45% (almost 1/2). The main cancer type for women is breast cancer, whereas
for men it is prostate (closely followed by lung). In 2020, the CR75 (crude rate at age 75)
is a whopping 31% for women and
35% for men. The risk after 75
years decreases, as this often
means that they’re genetically less
prone to developing cancer. In the
Netherlands, ~128 000 people are
diagnosed with cancer each year.
Descriptive cancer epidemiology is important, as there is an expected increase in
cancer diagnoses due to the ageing population and lifestyle. This means that we should
commit to preventative measures in order to prevent a further increase in numbers.
Studying the epidemiology of cancer, allows us to gain knowledge about trends in
incidence and survival/mortality after cancer and the knowledge can be used to
develop, implement and evaluate effective policies for cancer control (e.g. screening,
preventive measures, education and planning care facilities).
Key epidemiological concepts are prevalence, incidence, mortality and relative
survival.
,Prevalence
The prevalence refers to the number of people with cancer, divided by the population at
risk at a certain moment in time.
Incidence
The incidence refers to the number of newly diagnosed cases of cancer, divided by the
population at risk in a certain time period.
This can be expressed in:
• a number: absolute number of new cases
• CR (crude rate): number of new cases per 100 000 people per year
• ESR (European standardized rate): number of new cases per 100 000 people per
year, standardized for the age composition of Europe
• WSR (world standardized rate): number of new cases per 100 000 people per
year, standardized for the age composition of the world
Mortality
Mortality refers to the number of cases that died from cancer, divided by the population
at risk in a certain time period. This is expressed in terms similar to those for incidence.
Relative Survival
Relative survival refers to the % of cancer cases alive, divided by the % of people of the
same age and sex expected to be alive in the general population. This means that it
looks at the percentage of cancer cases alive at a certain time period after diagnosis,
excluding those who died of other causes.
Worldwide Differences
There are huge differences in cancer
incidence between countries, but also
between sex. On top of this, different
cancer types can be more prevalent in
some countries, such as stomach
cancer being more prevalent in countries such as China, due to their way of food
conservation and their susceptibility to helicobacter pylori. China is also more
susceptible to liver cancer, due to the presence of the aflatoxin and hepatitis B.
Cervical cancer is more prevalent in the south of Africa, mostly due to the presence of
the human papillomavirus. There are even national differences between cancer
incidence rates.
,In the Netherlands, the most common cancers for women are breast, skin, lung and
colorectal cancer; whereas for men, it is prostate, skin, lung and colorectal cancer. The
incidence of lung cancer in the Netherlands for men has decreased, whereas it has
increased for women. This could
be explained by the fact that
more women have started
smoking and less men smoke
compared to before. The total
mortality is increasing, but when
we look at the standardized
mortality, we see that it’s
actually decreasing. The relative
survival rate is also increasing,
compared to before.
Etiologic Cancer Epidemiology (Risk Factors)
Age
The most important risk factor for cancer in general is age. This is due
to the time needed for the accumulation of mutations in regulatory
genes, and thus damage, to daughter cells. These mutations can
happen in a spontaneous manner, due to chemical substances,
radiation or viruses.
There are, however, protective tools to prevent mutations. These
include DNA repair, apoptosis and senescence (mitosis stops).
Cancer at an older age is often due to the combination of accumulation of
damage/mutations in regulatory genes, more damage to repair tools, causing them to
be less effective and the loss of control by the micro-environment.
Life expectancy is increasing, and the grey pressure is increasing as well. This causes
an increase in new cancer diagnoses per year (by 25% when comparing 2007 and 2017).
However, survival has improved, causing the number of cancer deaths to only increase
by 13%. The number of patients alive per year has increased by 49%.
In short: due to the double ageing phenomenon (population is both increasing and
getting older), there are more cancer patients compared to before. We now do have a
better survival chance because of early detection and an improved treatment.
However, the diagnosis and treatment is more expensive. This means that we should
focus on prevention.
, Ways of Identifying Causes of Cancer
Accidental Finding
Nuns are at a high risk of breast cancer due to them not having children, and thus their
hormones being different. In the past, during X-rays, all the doctors and nurses would
be in the same room as the patient getting the X-ray. This caused cancer as well. In
1929, women painted the numbers onto watches with radium. They would dip the brush
in their mouth to shape the tip, this caused radium poisoning, and thus cancer. After
this was banned, the cancer cases dropped by a lot. Other accidental findings include
chrome-6 in paint, GenX in drinking water and TATA steel.
Systematic Counting / Trends
The first example is the discovery of retinoblastoma. Through looking at numbers, they
were able to show that both alleles need to be
mutated in order for the tumour to form. They also
found the cumulative risk of stomach cancer
through looking at numbers worldwide. They also
found that Japan-born migrants have a lower risk
of breast cancer, but a higher risk of stomach
cancer; whereas their children have a higher risk
of breast cancer and a lower risk of stomach
cancer. These risks respectively increase and
decrease even more with the second generation.
The trend in melanoma in the US also shows that there is an increase in risk, as there is
an increase in sunbathing popularity.
Focussed Research – Human Observational Studies
A case-control study can be set up to study
cancer epidemiology. An example is this study,
in which they looked at the association between
maternal stilbestrol therapy and cancer of
vagina. They first look at the disease, then the
exposure.
Alternatively, one could set up a prospective
cohort study, in which they first look at the
exposure, then the disease state.
A famous cohort study is the one that looked
into lung cancer and other causes of death in
relation to smoking. They discovered that
smoking is related to cancer of the lung,
bladder, stomach, intestine, …; but also cardiovascular diseases and impotence.
Cancer Epidemiology – Dr. Alina Vrieling
A lot is involved when it comes to the
oncological patient. Things such as
immunotherapy, systemic therapy,
pathology, chemical carcinogens,
genetics, but also epidemiology.
Cancer epidemiology refers to both
the etiology (the cause of a disease or
the science that deals with such
causes) and the cancer itself.
In this lecture, we shall talk about descriptive cancer epidemiology, etiologic cancer
epidemiology (risk factors) and cancer epidemiology in Nijmegen.
Descriptive Cancer Epidemiology
The lifetime risk of cancer in females is 38% (>1/3) and the lifetime risk of cancer in
males is 45% (almost 1/2). The main cancer type for women is breast cancer, whereas
for men it is prostate (closely followed by lung). In 2020, the CR75 (crude rate at age 75)
is a whopping 31% for women and
35% for men. The risk after 75
years decreases, as this often
means that they’re genetically less
prone to developing cancer. In the
Netherlands, ~128 000 people are
diagnosed with cancer each year.
Descriptive cancer epidemiology is important, as there is an expected increase in
cancer diagnoses due to the ageing population and lifestyle. This means that we should
commit to preventative measures in order to prevent a further increase in numbers.
Studying the epidemiology of cancer, allows us to gain knowledge about trends in
incidence and survival/mortality after cancer and the knowledge can be used to
develop, implement and evaluate effective policies for cancer control (e.g. screening,
preventive measures, education and planning care facilities).
Key epidemiological concepts are prevalence, incidence, mortality and relative
survival.
,Prevalence
The prevalence refers to the number of people with cancer, divided by the population at
risk at a certain moment in time.
Incidence
The incidence refers to the number of newly diagnosed cases of cancer, divided by the
population at risk in a certain time period.
This can be expressed in:
• a number: absolute number of new cases
• CR (crude rate): number of new cases per 100 000 people per year
• ESR (European standardized rate): number of new cases per 100 000 people per
year, standardized for the age composition of Europe
• WSR (world standardized rate): number of new cases per 100 000 people per
year, standardized for the age composition of the world
Mortality
Mortality refers to the number of cases that died from cancer, divided by the population
at risk in a certain time period. This is expressed in terms similar to those for incidence.
Relative Survival
Relative survival refers to the % of cancer cases alive, divided by the % of people of the
same age and sex expected to be alive in the general population. This means that it
looks at the percentage of cancer cases alive at a certain time period after diagnosis,
excluding those who died of other causes.
Worldwide Differences
There are huge differences in cancer
incidence between countries, but also
between sex. On top of this, different
cancer types can be more prevalent in
some countries, such as stomach
cancer being more prevalent in countries such as China, due to their way of food
conservation and their susceptibility to helicobacter pylori. China is also more
susceptible to liver cancer, due to the presence of the aflatoxin and hepatitis B.
Cervical cancer is more prevalent in the south of Africa, mostly due to the presence of
the human papillomavirus. There are even national differences between cancer
incidence rates.
,In the Netherlands, the most common cancers for women are breast, skin, lung and
colorectal cancer; whereas for men, it is prostate, skin, lung and colorectal cancer. The
incidence of lung cancer in the Netherlands for men has decreased, whereas it has
increased for women. This could
be explained by the fact that
more women have started
smoking and less men smoke
compared to before. The total
mortality is increasing, but when
we look at the standardized
mortality, we see that it’s
actually decreasing. The relative
survival rate is also increasing,
compared to before.
Etiologic Cancer Epidemiology (Risk Factors)
Age
The most important risk factor for cancer in general is age. This is due
to the time needed for the accumulation of mutations in regulatory
genes, and thus damage, to daughter cells. These mutations can
happen in a spontaneous manner, due to chemical substances,
radiation or viruses.
There are, however, protective tools to prevent mutations. These
include DNA repair, apoptosis and senescence (mitosis stops).
Cancer at an older age is often due to the combination of accumulation of
damage/mutations in regulatory genes, more damage to repair tools, causing them to
be less effective and the loss of control by the micro-environment.
Life expectancy is increasing, and the grey pressure is increasing as well. This causes
an increase in new cancer diagnoses per year (by 25% when comparing 2007 and 2017).
However, survival has improved, causing the number of cancer deaths to only increase
by 13%. The number of patients alive per year has increased by 49%.
In short: due to the double ageing phenomenon (population is both increasing and
getting older), there are more cancer patients compared to before. We now do have a
better survival chance because of early detection and an improved treatment.
However, the diagnosis and treatment is more expensive. This means that we should
focus on prevention.
, Ways of Identifying Causes of Cancer
Accidental Finding
Nuns are at a high risk of breast cancer due to them not having children, and thus their
hormones being different. In the past, during X-rays, all the doctors and nurses would
be in the same room as the patient getting the X-ray. This caused cancer as well. In
1929, women painted the numbers onto watches with radium. They would dip the brush
in their mouth to shape the tip, this caused radium poisoning, and thus cancer. After
this was banned, the cancer cases dropped by a lot. Other accidental findings include
chrome-6 in paint, GenX in drinking water and TATA steel.
Systematic Counting / Trends
The first example is the discovery of retinoblastoma. Through looking at numbers, they
were able to show that both alleles need to be
mutated in order for the tumour to form. They also
found the cumulative risk of stomach cancer
through looking at numbers worldwide. They also
found that Japan-born migrants have a lower risk
of breast cancer, but a higher risk of stomach
cancer; whereas their children have a higher risk
of breast cancer and a lower risk of stomach
cancer. These risks respectively increase and
decrease even more with the second generation.
The trend in melanoma in the US also shows that there is an increase in risk, as there is
an increase in sunbathing popularity.
Focussed Research – Human Observational Studies
A case-control study can be set up to study
cancer epidemiology. An example is this study,
in which they looked at the association between
maternal stilbestrol therapy and cancer of
vagina. They first look at the disease, then the
exposure.
Alternatively, one could set up a prospective
cohort study, in which they first look at the
exposure, then the disease state.
A famous cohort study is the one that looked
into lung cancer and other causes of death in
relation to smoking. They discovered that
smoking is related to cancer of the lung,
bladder, stomach, intestine, …; but also cardiovascular diseases and impotence.
