Jack Carew: Hi, everyone, and welcome to this module
on the Global Burden of Cancer.
In this presentation, we have three main goals.
So first, we're going to define cancer.
Then we're going to survey cancer incidence
and prevalence in the US and globally.
And finally, we're going to describe cancer mortality
in the US and globally.
So to begin with, what is cancer?
Well, cancer can be succinctly defined
as deranged cell division.
It's the uncontrolled growth and spread
of abnormal cells in the body.
It can arise from virtually any tissue in the body
and are usually named with the anatomic site of origin.
That being said, the vast majority of all cancers
are solid tumors that originate in epithelial cells.
Epithelial cells are the lining
of different organs of the body,
including those of the gastrointestinal tract,
the genitourinary tract, and the reproductive tract.
And because these cancers make up so many of the cases
that afflict humans and cause death in humans,
they'll be the great focus of this course.
So that being said too,
we have about 90% cancers in epithelial cells.
We have some smaller categories of cancers
that while they don't affect as many people
or cause as many cases,
are nonetheless then important to know.
So 8% of malignant neoplasms or cancers
arise from cells of the immune system.
Less than 2% happen in connective tissues
and less than 1% develop in the central nervous system.
And cancer can cause death by metastasizing
or spreading to vital organs
and really making the functions of those organs impossible
and shutting down these biological processes
that are necessary for life.
And while we've made a lot of progress in both the medical
and the public health field over the past number of years,
it's unfortunate but many forms of cancer
still remain incurable and are responsible
for significant mortality in the US and globally.
So kind of reflecting that too, we have this quotation
from a book titled "The Pathologic Basis of Disease"
that came out in 1974.
And when we think about cancer,
we still feel a lot of these things.
It's a scary disease and it really is responsible
both for a medical and a biologic burden
as well as social effects,
effects on one's family, one's livelihood.
And these are all kind of themes
that we'll keep in mind over the coming weeks
and that we'll have opportunities to explore
in discussion posts and projects.
So to speak a little bit about the global burden of cancer,
in 2020, there were 19.29 million new cases of cancer
and 9.96 million cancer deaths.
And all these data are from GLOBOCAN
are the Global Observatory of Cancer.
And this is a really great resource
for updated cancer statistics that span mortality incidence,
prevalence, different sexes, and different cancer sites
in different parts of the world.
So in the future, when we're doing discussion posts
and when we're working on projects,
this is a really great resource
for getting accurate, updated information
about different questions
or different research areas that you have.
So more men experience cancer than women.
In 2020, that was a difference of about 1 million cases.
And more men also die of cancer than women.
So the number of deaths
in men was about 25% higher than among women.
And the age-standardized cancer incidence in men
was 19% higher than in women.
So about 222 people per 100,000 people
or men had cancer versus 186 per 100,000.
So to talk a little bit about the specific cancer types,
lung cancer was by far the deadliest malignancy
and it caused 18% of total cancer deaths in 2020.
And we see from this, or after lung cancer,
the number of cases really decreased quite significantly.
So of all other cancer types, no single cancer type
is causing more than 1 million deaths in 2020.
We see that colon and rectum cancer come close,
but the rest are all killing under a million people in 2020.
So still obviously significant mortality numbers,
but really lung cancer is a significant driver
of mortality among cancers.
So next, if we look at the ratio of mortality to incidence,
which isn't a perfect measure of fatality
but is a pretty good estimate,
we see it's highest for pancreatic cancer,
liver cancer, lung cancer, and esophageal cancer.
And there's a number of reasons for this ratio
and we're going to dig into them a little bit
over the coming weeks.
And finally, cancer deaths constitute approximately 13.5%
of the 60 million annual deaths worldwide.
And that's a 2012 statistic.
And you'll note that your textbook
relies on statistics from 2012.
So a lot of times we'll see those
and I'll do my best to present the updated statistics
where it's relevant.
And a lot of times the trends have continued
from 2012 to 2020 and 2022.
But because a lot of the examples that your book uses
are going to be from the early 2010s,
the course will also discuss those in depth.
So worldwide, cancer is the third leading cause of death
behind heart disease and infectious conditions.
But that being said, in high-income countries,
which are abbreviated as HICs,
cancer is the leading cause of death
in people under the age of 85 years.
So it's surpassed heart disease
and has become the leading cause of death.
And we'll see too, one of the other themes
that we'll explore in this course
is the differences in cancer mortality
and incidence among different areas of the world.
So we'll look at high-income countries, or HICs,
and low and middle-income countries, or LMICs,
and look at the ways that rates are increasing
or decreasing and some of the reasons for those changes.
So as I mentioned, the global burden of cancer
is higher in men than women.
And this is looking at those 2012 statistics
that are going to be listed in your textbook.
So the number of cancer deaths among men
was 31% higher than among women.
And the age-standardized cancer incidence in men
was 24% higher than in women.
So, pretty much higher in men.
We see this figure
that really, clearly shows the differences.
And again, I'll draw your attention
to the really high burden
that lung cancer wages on mortality.
So of this 2012 data, we see that liver, lung, stomach,
as well as the other major cancers that I mentioned
are really causing the bulk of the mortality
when we talk about cancer in men.
And we're going to spend the next number of weeks digging
into each of these cancers one at a time
to really explore their role in incidence and mortality,
some of the risk factors,
and the ways to prevent these cancers.
And finally, the chart for the global cancer deaths in women
as we'll see, is similar as it is for men,
though you'll note that in the left hand,
the scale on the left hand of the graph is much lower
than it was for men.
So for men, the chart reached up to a million or 1,100,000.
And here the legend only reaches up to 600,000
because the number of deaths in women
is so much less than it is in men.
And finally, to briefly mention this difference
that a lot of cancers are due to cells
of the epithelial tract
or rather epithelial cells
that are located in many tracts of the body.
And this nine-to-one prominence of carcinomas
are in cancers of the epithelial cells
relative to other forms of cancer
really shows how much faster these cells are dividing
than other cell populations in the body.
So for example, the cells of the gastrointestinal tract
are dividing at such a faster rate
than muscle cells or fat cells or bone cells,
and it's this rapid cell division
that really creates opportunities for cancers to form
and exist in a human's body.