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Hello, my name is Marc Tischkowitz.
I am a Reader in Medical Genetics
at the University of Cambridge.
And this lecture is an introduction
to cancer genetics.
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I have no conflicts of
interest to disclose.
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Learning objectives: so the topics we're
gonna cover are an introduction to
the principles of cancer genetics.
We're going to examine
how to make a timely and
accurate initial family
history assessment.
We're going to describe
how to confirm cancers and
use histology to guide testing for
hereditary cancer predisposition.
We're gonna look at how to become
confident in using communicating risk in
cancer genetics.
And we're gonna cover some of the common
inherited cancers such as breast,
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ovarian, and colorectal.
So to get going,
we are gonna talk a bit about sporadic
cancers versus inherited cancers.
So this slide shows a copy
of a DNA molecule and
how it can become mutated.
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The original idea of hereditary cancer
predisposition was developed by
Alfred Knudson.
His theory was called
a two-hit hypothesis.
And his idea was that you
have cells divide and
divide over a lifetime and
you develop one mutation.
And then you develop a second
mutation over a long period of time.
So this could be many decades.
And eventually you develop a cancer,
once you've got these two mutations.
And this shows the cancer developing.
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Next slide covers hereditary
cancer predisposition.
And here you have the egg and the sperm
and one or other has a gene mutation.
They come together.
In this situation,
the individual is already born with one
copy mutated in every cell in the body.
As this is an inherited mutation,
the second mutation occurs.
But the timeframe for
this can be much shorter,
because there's already one mutation
in all the cells in the body.
And again, you would develop normal cells
and cancer cells in this situation.
And the cancer cells would develop
after the second mutation.
And because all the cells already
have one mutation, the timing for
this is much faster than
in a sporadic setting.
This explains why hereditary cancers
due to germline mutations typically
occur several decades earlier
than sporadic cancers.
So if you think about sporadic cancers,
two thirds of all cancers occur after
the age of 65, which is when most
of these sporadic cancers occur.
For hereditary cancers,
they tend to occur under the age of 50.
So they tend to be much earlier.
