Jack: Hi, everyone.
In today's lecture, we'll be discussing global trends
in cancer morbidity and mortality.
So the three goals of this lecture,
to summarize global cancer trends,
to draw comparisons between cancer rates in men and women,
and between cancer in high-income countries
and low and middle-income countries, or LMICs,
and discuss the epidemiological transition of cancer
and its implications for future cancer incidents.
So to begin with,
we're looking at figure 2.3 in the textbook
"Global Cancer Trends: Cases and Deaths,"
and we see that the number of cases
has increased from approximately 10 million in 2000
to approximately 14 million in 2012.
We also see that the number of deaths from cancer
has increased from about 6 million in 2000
to approximately 8 million in 2012.
It's also important to realize
that even though the raw numbers or the absolute numbers
of cancer cases and deaths have increased,
the cancer rates have actually decreased during that time
because of an increase in population.
So we can attribute a lot of this increase
to the growth in aging of the world's population.
We also see that life expectancy
increased over this period from 68 to 71 years,
and because the majority of cancers
are diagnosed later in life,
elderly populations are expected
to have higher crude, or unadjusted rates, of cancer
than young populations.
Next, when we divide the trends
in cancer mortality between men and women,
as I noted before,
we see that there's a slight decrease in mortality rates.
So that is deaths per a hundred thousand people
decreased for both men and women between 2000 and 2012.
So we see, thus, that the age standardized rates of cancer
show these decreasing rates of cancer mortality
even though cancer incidence is slightly increasing.
When we look at, as the textbook calls,
developing or developed nations,
or is going to refer to them as high-income countries
and low and middle-income countries,
we see that there's very different profiles
of cancer mortality between these groups of countries.
So among men living in developing nations,
the total number of deaths
due to either liver cancer or stomach cancer
was four times higher than in developed nations,
reflecting high rates of infection by liver viruses
like hepatitis B or hepatitis C virus
and stomach bacteria,
so primarily Helicobacter pyloris.
We also see that there's a contamination
of food supplies by molds
that produce highly-carcinogenic alpha toxins.
Also, reciprocally, we see
that deaths from colorectal cancer or prostate cancer
occurred more frequently in developed nations,
partially due to intakes of diets
high in fat and calories and low in fiber,
fruits and vegetables.
And lung cancer and other cancers
arising from tobacco smoking
caused the most male deaths in all populations.
Among women, breast cancer is the leading cause of death
in both developing and developed nations.
Among women living in low and middle-income countries,
cancer of the uterine cervix, or cervical cancer,
is the second leading cause of death
principally due to a lack of screening
for pre-malignant dysplastic lesions of the cervical mucosa.
Lung cancer causes nearly as many deaths as breast cancer
in high-income countries, and rising rates
of smoking among women worldwide
have resulted in increasing numbers
of female lung cancer deaths in all populations.
Finally, death from stomach cancer or liver cancer
occurs more frequently
in low and middle-income countries,
whereas cancers of the colon, and rectum,
pancreas, and ovaries cause relatively more deaths
in high-income countries.
When we turn to look at the US,
we have these predicted statistics from 2022.
So while the numbers haven't completely been calculated yet,
it's predicted that there'll be
1.9 million new cancer diagnoses in the US,
and breast cancer is the most common cancer diagnosis.
In the same year, 609,360 people
are predicted to die of cancer.
And the leading cause of mortality among cancers
is lung and bronchus cancer.
We see in the US
that cancer mortality and incidence rates vary considerably
by race and by gender for a number of reasons.
Men have about a 30% higher cancer death rate than women.
And African American men have the highest death rates
from cancers of the lung, and bronchus,
prostate, and colon, and rectum
compared to any other racial or ethnic group in the US.
When we look at a graph of,
I believe this is cancer mortality in men,
we see some really stark differences between cancer types.
So to begin with, more than half of cancer deaths in US men
are due to cancers of the lung, and bronchus,
prostate, colon, and rectum,
and we see that represented
by the highest lines on the graph here,
the darker blue solid line and the blue dashed line.
While lung cancer mortality
has declined slightly since about 1990,
the male death rates from lung cancer
are still more than double that of other anatomic sites.
We also see that in 1987,
prostate cancer surpassed colorectal cancer
as the second leading cause of cancer death in men,
and that during the past decade,
the mortality rates from both prostate cancer
and colorectal cancer show evidence of a gradual decline.
Mortality rates from other malignancies
have remained constant,
with the exception of the rates for stomach cancer,
which have declined dramatically, beginning in about 1930.
When we turn to look at cancer mortality rates in women,
we see the cancer of the lung and bronchus,
breast, and colon and rectum
account for more than half of all cancer deaths.
In 1987, lung cancer surpassed breast cancer
as the leading cause of cancer death in women.
And since 1950, lung cancer mortality among women
has increased by more than 600%
and now accounts for about 25% of all female cancer deaths.
We also see that breast cancer mortality
remained remarkably constant throughout the 20th century,
but now appears to be slightly declining.
Mortality rates from cervical cancer
and stomach cancer declined dramatically
from the 1930 to 2011 time period.
And colorectal cancer mortality
has gradually declined since the 1950s.
Finally, when we look at this figure 2.9 from your textbook
about the epidemiologic transition of cancer
by age and economic region,
we see some key differences between different age groups
and different geographic regions in the world.
So the 2014 World Cancer Report
released by the World Health Organization, or the WHO,
warns of an impending tidal wave of cancer
in many populations of the world.
The reason why this is
is because of the epidemiologic transition
which states that chronic diseases like cancer
are gradually replacing acute diseases
in the aging world population.
So we see an increase of chronic diseases
like cancer and heart disease
and a decrease in infectious diseases, primarily.
This figure shows the increasing proportion
of incident cancers or cancer incidents
in older versus younger adults since 1980,
and the corresponding data for LMICs and HICs.
During the period 1980 to 2010,
the proportion of cancer incidents diagnosed
among people living in economically-developing regions
increased from 50% to 65%,
and the proportion of new cases diagnosed
in people over 65 years of age
increased from 35% to 55%.
Clearly, the greatest increases in cancer rates
have occurred in elderly populations
of low and middle-income nations.
Approximately 60% of new cancer cases
and 70% of all cancer deaths
now occur in Africa, Asia,
Central America, and South America.
Such populations have a virtual perfect storm
of increasing longevity,
coupled with predisposing behavioral factors
and conditions that increase cancer risk.
These conditions or these factors
include addiction to tobacco and alcohol,
unhealthy nutrition, obesity, physical inactivity,
and widespread exposure
to certain sexually transmitted infectious agents
that predispose to malignant transformation
like HPV and other sexually-transmitted infections.