June 2015
https://sites.google.com/site/surgerypaper/2015/targeted-therapy-for-treatment-of-cancer
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Understanding Targeted Therapy
Approved by the Cancer.Net
Editorial Board, 01/2019
Targeted therapy is a cancer treatment that
uses drugs. But it is different from
traditional chemotherapy, which also uses drugs to treat cancer. Targeted therapy works by
targeting the cancer’s specific genes, proteins, or the tissue environment that
contributes to cancer growth and survival. These genes and proteins are found in cancer cells or in
cells related to cancer growth, like blood vessel cells.
Doctors often use targeted
therapy with chemotherapy and other treatments. The U.S. Food and Drug Administration
(FDA) has approved targeted therapies for many types of cancer. Scientists are
also testing drugs for new cancer targets.
The “targets” of targeted therapy
It is helpful to know how cancer
cells grow in order to better understand how targeted therapy works. Cells make
up every tissue in your body. There are many different cell types, such as
blood cells, brain cells, and skin cells. Each type has a specific function.
Cancer starts when certain genes in healthy cells change. This change is called
a mutation.
Genes tell cells how to make
proteins that keep the cell working. If the genes change, these proteins
change, too. This makes cells divide abnormally or live too long. When this
happens, the cells grow out of control and form a tumor. Learn more about the
genetics of cancer.
Researchers are learning that specific
gene changes take place in certain cancers. So they are developing drugs that
target the changes. The drugs can:
Block or turn off signals that tell cancer cells to grow and divide
Keep cells from living longer than normal
Destroy the cancer cells
Types of targeted therapy
There are several types of targeted therapy:
Monoclonal antibodies. Drugs called
“monoclonal antibodies” block a specific target on the outside of cancer cells
and/or the target might be in the area around the cancer. These drugs work like
a plastic cover you put in an electric socket. The plug keeps electricity from
flowing out of the socket.
Drugs called “monoclonal antibodies” block
a specific target on the outside of cancer cells and/or the target might be in
the area around the cancer. These drugs work like a plastic
Monoclonal antibodies can also send toxic
substances directly to cancer cells. For example, they can help chemotherapy
and radiation therapy get to cancer cells better. You usually get these drugs
injected into a vein, or "intravenously" (IV).
Small-molecule drugs. Drugs called
“small-molecule drugs”can block the process that helps cancer cells multiply
and spread. These drugs are usually taken as pills. Angiogenesis inhibitors are
an example of this type of targeted therapy. These drugs keep tissue around the
tumor from making blood vessels. Angiogenesis is the name for making new blood
vessels. A tumor needs blood vessels to bring it nutrients. The nutrients help
it grow and spread. Anti-angiogenesis therapies starve the tumor by keeping new
blood vessels from forming.
Matching a patient to a treatment
Studies show that not all tumors
have the same targets. So the same targeted treatment will not work for
everyone. For example, a gene called KRAS (pronounced kay-rass) controls the
growth and spread of a tumor. About 40% of colorectal cancers have this gene
mutation. When this happens, the targeted therapies cetuximab (Erbitux) and
panitumumab (Vectibix) are not effective. If you have colorectal cancer, it is
helpful to be tested for the KRAS mutation. This would help your doctor give
you the most effective treatment. It also protects you from unnecessary side
effects.
Some treatments, called
"tumor-agnostic" or "site-agnostic treatments," are not
specific to a certain type of cancer. Instead, they focus on a specific genetic
change and are used to treat tumors anywhere in the body. A tumor may also be
tested for other genetic changes, including BRAF and HER2. These markers do not
have FDA-approved targeted therapies yet, but there may be opportunities in
clinical trials that are studying these changes. Learn more about
tumor-agnostic treatments.
Recently, the FDA approved
larotrectinib (Vitrakvi) as a type of targeted therapy that focuses on a
specific genetic change called an NTRK fusion. This type of genetic change is
found in a range of cancers. Larotrectinib is approved for these cancers that
are metastatic or cannot be removed with surgery and have worsened with other
treatments.
Your doctor might order tests to
learn about the genes, proteins, and other factors in your tumor. This helps
find the most effective treatment. Many targeted therapies cause side effects.
Also, they can be expensive. So, doctors try to match every tumor to the best
possible treatment.
Examples of targeted therapies
Below are a few examples of targeted therapies. Ask your health
care team for more information.
Breast cancer. About 20% to 25% of
all breast cancers have too much of a protein called human epidermal growth
factor receptor 2 (HER2, pronounced her-too). This protein makes tumor cells
grow. If the cancer is HER2 positive, several targeted therapies are available.
Learn more about targeted therapy for breast cancer.
Colorectal
cancer. Colorectal cancers often make too much of a protein called
epidermal growth factor receptor (EGFR). Drugs that block EGFR may help stop or
slow cancer growth. These cancers have no mutation in the KRAS gene. Another
option is a drug that blocks vascular endothelial growth factor (VEGF,
pronounced vedge-eff). This protein helps make new blood vessels. Learn more
about targeted therapy for colorectal cancer.
Lung cancer. Drugs that block the
protein called EGFR may stop or slow lung cancer growth. This may be more
likely if the EGFR has certain mutations. Drugs are also available for lung
cancer with mutations in the ALK and ROS genes. Doctors can also use
angiogenesis inhibitors for certain lung cancers. Learn more about targeted
therapy for non-small cell lung cancer.
Melanoma. About
half of melanomas have a mutation in the BRAF gene (pronounced bee-raff).
Researchers know specific BRAF mutations make good drug targets. So the FDA has
approved several BRAF inhibitors. These drugs can be dangerous if you do not
have the BRAF mutation. Learn more about targeted therapy for melanoma.
The list above does not include
every targeted therapy. Researchers are studying many new targets and drugs.
You can learn more about targeted therapy in each cancer-specific section on
Cancer.Net in the Treatment Options and Latest Research pages. You can also
learn more about the latest targeted therapy research on the Cancer.Net blog.
It may seem simple to use a drug
that works on your specific cancer. But targeted therapy is complex and not
always effective. It is important to remember that:
A targeted treatment will not work if the
tumor does not have the target.
Having the target does not mean the tumor
will respond to the drug.
The response to treatment may be temporary.
For example, the target may not
be as important as doctors first thought. So the drug may not help much. Or the
drug might work at first but then stop working. Finally, targeted therapy drugs
may cause serious side effects. These are usually different from traditional
chemotherapy effects. For example, people receiving targeted therapy often have
skin, hair, nail, or eye problems.
Targeted therapy is an important
type of cancer treatment. But so far, doctors can only get rid of a few cancers
using only these drugs. Most people also need surgery, chemotherapy, radiation
therapy, or hormone therapy. Researchers will develop more targeted drugs as
they learn more about specific changes in cancer cells.
