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Lecture 9

HLTH101 Lecture Notes - Lecture 9: Micrometastasis, Genotoxicity, Benzene

Health Studies
Course Code
Glenn Ward

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HLTH 101
Fall, 2012
This lecture will serve as our introduction to cancer. We will begin by
discussing the current status of cancer as a disease: its incidence and
prevalence, mortality and morbidity. We’ll see that the detection of cancer is a
major issue in determining mortality rates that are meaningful for our
understanding of the success or failure of treatment as well as of changes in the
incidence rate due to changes in risk factors. To understand this issue, we’ll need
to understand some of the types of bias that can result from screening practices.
It is vital that you understand these biases, so be sure to attend the lecture and
keep careful notes!
We’ll then discuss some of the basic concepts of cancer derived from
research over the past few decades. Much of this discussion will focus on
terminology and definitions, and so you should expect to have to spend some
time on remembering specific terms as well as understanding the underlying
concepts. Be sure to download the figures referred to on the next page. They will
be invaluable in helping you to understand the concepts.
Note that the notes for much (but not all) of this lecture are available at the
end of this file. Be sure to study them carefully after downloading the figures
from the web.
Supplemental Readings:
This is a link to the Canadian Cancer Society’s website in general and to
statistical data in particular. I’ll be showing many of the slides for statistics
from 2012 (seen at the top part of the box in the middle of the page). You
may wish to download them yourselves. You may prefer to have a hard
copy of the report Canadian Cancer Statistics 2012, in which case you
should go to the following link:
and then click on the appropriate link for the pdf.
This brief (2 page) editorial, from the journal The Oncologist, summarizes
many of the points I will make in the lecture on the Impact of Cancer.

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HLTH 101
Fall, 2012
This is the graphic depicting the concepts, to be explained in the lecture, of
anaplasia and monoclonality.
These four links are very general introductions to the concepts of initiation,
promotion, progression and metastasis. Be sure to click on the link on the
left of the second reading for diagram Fig. 15.4, and be sure to make a copy
of all of the drawings and figures in the other links.
This is a diagram demonstrating the relationship between initiation and
the terms cancer, neoplasia and malignancy are often used interchangeably
generally, cancer is used to describe the disease involving neoplasia (roughly
meaning growth of new tissue)
malignancy refers to the later stage of cancer in which the growth has spread to
other tissues
in Canada:
the lifetime cancer risk is:
greater than 40% for women
greater than 45% for men
cancer is also the cause of 25% of all deaths
in 2009 there were 171,000 new cases of cancer and 75,300 deaths due to
incidence and mortality rats reflect that fact that cancer is a late-onset disease
incidence rate is highest for those in their 60’s

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HLTH 101
Fall, 2012
mortality rates are highest for those in their 70’s and 80’s
mortality rates generally decline after age 90
cancer is the 2nd leading cause of death in Canada and most of the developed
after age 75 it is the leading cause of death
cancer has the greatest numbers of YLL
between ages 45-64 cancer deaths are greater than the next 3 causes
1971: U.S. President Nixon signs the “National Cancer Act”, commonly known as
the "war on cancer"
after 40 years, has the war been won?
in fact, it has been difficult to show beyond a doubt that the “war” has been
this can be contrasted with the case of cardiovascular disease, for which
deaths have declined by 50% or more in Canada over the past 30 years
if it’s not clear that we have made substantial gains in reducing incidence
rates and mortality due to cancer, this is likely due mainly to three unique
challenges to the study of cancer
i) determination of the size of the problem
recall that incidence and mortality rates are often used to establish the “size”
of a health problem
a) incidence rates
cancer incidence rates actually increased for at least 25 years after the
war on cancer was initiated
a little over a decade ago, the age-adjusted incidence rate for
cancer finally started to decrease
could the initial increase in incidence rates actually be due to the
effects of increases in the diagnosis of cancer rather to a real
increase in the cancer rate?
there are at least two possible reasons for an increase in diagnosis
1) publicity campaigns heightening the awareness of early detection
for cancer can often lead to more diagnoses of cancer
2) the development of early detection techniques that may detect
cancers that would have been missed in earlier times
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