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Precision Medicine: Targeted Therapy


Welcome to this quick
guide on Precision Medicine:
Targeted Therapies. A targeted therapy works
against a molecule that is specific to your
cancer cells. In your body, these
molecules, or “targets” tend to play a important
role in helping your cancer cells to survive
or spread. Chemotherapy and
targeted therapy work in different ways. Chemotherapy
destroys all fast- growing cells,
regardless of whether the cells are part of
your cancer or not. Targeted therapies are
like puzzle pieces that fit together with
their targets inside your body. This allows the therapy
to stop specific molecules that your
cancer needs to grow and spread. Your genes-
sometimes called your DNA -are molecules
that control how your body makes other
molecules, called proteins. Molecular “targets”
that targeted therapies work against are also
called biomarkers. Biomarkers can be
genes or proteins. They can also be
normal and abnormal cells in your blood. To learn more about
biomarkers, see our quick guide on
Precision Medicine: Biomarker Testing. Your cells, whether
they are cancer cells or normal cells, are
made up of thousands of genes and proteins. Targeted therapies are
like puzzle pieces that fit together with
their targets inside your body. This allows the
therapy to stop specific molecules that your
cancer needs to grow and spread. There are different
types of targeted therapies. They tend to be either
small molecules or monoclonal antibodies. Small molecule
targeted therapies can be taken by swallowing
a pill. They act on targets
that are inside of cancer cells. Monoclonal antibody
targeted therapies are injected into a vein
using an IV. They act on targets
on the outside of cancer cells. There are many ways
that targeted therapies work against cancer.
These include: -Tagging cancer cells.
When monoclonal antibodies stick to the
surface of your cancer cells they act as tags. This makes it easier
for your own immune system to find and
destroy those cells. -A second way that
targeted therapies work against cancer is
finding and destroying cancer cells directly. Both small molecules
and certain types of monoclonal antibodies
can stick to targets in or on the surface of
your cancer cells and then kill those
cancer cells directly. -A third way that
targeted therapies work against cancer is by
cutting off the blood supply that tumors need to
survive. Some targeted
therapies stop tumor growth by cutting off
the blood supply to the tumor. Blood vessel growth is
also called “angiogenesis”. A fourth way that
targeted therapies work against cancer is
by cutting off the hormone supply that
some tumors use grow and survive. For these types of
cancers, targeted small molecule
therapies can stop tumor growth by
stopping your body from making or using
the hormones that your tumor needs to
survive. A final way that
targeted therapies work against cancer is
by taking the “brakes” off the immune
system. To keep your immune
system from attacking your healthy cells,
your body has safeguards in place. These are called
“checkpoints”. Some cancers are able
to control checkpoints. This allows the cancer
to avoid being killed by the immune system. Targeted therapies
aim to remove these checkpoints. Some targeted
therapies take the “brakes” off your
immune system, to help your body
fight cancer. To learn more about
these types of therapies, see our
quick guide on Immunotherapy. Even if your tumor has
a molecule that matches up with a
targeted therapy, it doesn’t mean that the
therapy will work on your cancer. Or the therapy may
work for a while and then stop working. One reason for this is
that cancer cells are far more likely to
change, or “mutate”, than normal cells. This means that the
target can change… Or another reason
why targeted therapy may not work is that
the cancer has figured out a way to grow
without using the molecule that the
therapy is blocking. Sometimes targeted
therapies work best when they are given in
combination with other targeted therapies or
with chemotherapy. Sometimes, when a
patient experiences a side effect from a
targeted therapy, it means that the
therapy is working. For example, lung
cancer patients who develop a skin rash
while taking therapies that target EGFR are
more likely to respond to the treatment than
patients who do not develop a skin rash. This is because EGFR
is a molecule that is found in large
amounts in non-small cell lung cancer cells,
but is also found in very small amounts in
normal skin cells. That’s why a skin rash
is a sign that EGFR- targeted therapies are
hitting their target effectively. If you are interested in
learning more about how targeted
therapies can be used to treat your cancer,
the first step is to ask your doctor about
targeted treatments that might make sense
for you. Let’s watch a quick
scenario about how a conversation with your
doctor about targeted therapy might go. Your job is to help this
patient with stomach cancer ask his doctor
about using targeted therapies. Doctor: Those are my
treatment recommendations. Do you have any
questions for me? Patient: Are any of the
treatments you recommended targeted therapies? Doctor: Sometimes
patients with stomach cancer respond well to
targeted therapies that cut off the blood
supply to the tumor, or to therapies that target
a protein called HER2. Patient: Is that type of
therapy right for me, and do we need to do
any tests to find out? Doctor: I’m hopeful
that the chemotherapy I’m recommending will
work. If it turns out that we do want to add
another treatment, then we can send a
sample of your tumor to a lab to be tested
for HER2. Patient: Should we do
that test now? Doctor: Not
necessarily. I think we should start with the
chemotherapy and see how your cancer
responds. If we need to explore
additional treatments, we can talk about
testing your tumor for HER2. We can also start
looking into clinical trials. Sometimes, as
part of a clinical trial, you can have your
tumor biomarkers tested for free. I’ll give
you some information about clinical trials so
you can begin learning about your options.

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