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Targeted therapies are drugs that interfere with molecular
targets—things like proteins, genes and hormones. These targets can be on the
cancer cell itself or on other cells the cancer needs to help it grow and
spread. The target can also be inside cells. Normal cells do not have these
targets. As a result, targeted therapy is very specific to cancer cells. Lab tests
are usually performed on biopsy tissue to determine if eligible targets are
present, and whether or not the patient is an eligible treatment candidate.
Targeted therapy is different from standard chemotherapy.
Standard chemotherapy works by killing rapidly dividing
cells, such as cancer cells. However, your body also has normal rapidly
dividing cells, including hair follicles, bone marrow, and the lining of the
digestive tract. Standard chemotherapy will also kill many of these cells. This
accounts for many of the side effects and toxicities of standard chemotherapy.
Targeted therapy does not harm normal cells because they
lack the molecular targets it engages. Because of this, targeted therapy does
not have the same side effects as standard chemotherapy. There are side
effects, but they are different and people tend to tolerate them better. The
side effects vary depending on the type of targeted therapy.
There are two main types of targeted therapy.
The two main types of targeted therapy include:
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Monoclonal
antibodies use targets on the surface of cancer cells. When they attach to
these targets, they interfere with the cancer cell’s ability to grow. They can
also carry toxic substances directly to the cancer cell using these surface
targets. Growth factors outside the cancer cell are other targets for
monoclonal antibodies. These drug names end with –mab, for monoclonal antibody. -
Small
molecules can go inside cells to act on a target. This includes both cancer
cells and other kinds of cells that perform functions the cancer cell needs to
grow and spread. Enzymes are often targets of these small molecule drugs.
Interfering with or inhibiting enzymes stops various cellular functions. These
drug names end with –ib, for inhibit.
Immunotherapy can be a form of targeted therapy.
Cancer treatment guidelines typically list immunotherapy as
a separate category of cancer therapy. Malignant tumors are often able to fool
the immune system and grow without detection. Immunotherapy is any therapy that
boosts your own immune system to fight cancer. There are various ways to do
this, including using interferons, interleukins, and cancer vaccines.
Monoclonal antibody therapy—one of the targeted therapy
classes—is also an immunotherapy. Your healthy immune system already uses
antibodies to fight infections. Monoclonal antibodies are made in a lab to perform
specific functions. Therapeutic monoclonal antibodies can target cancer cells
or immune system pathways to increase your immune system’s ability to recognize
and fight the cancer.
Hormone therapy can be a form of targeted therapy.
Like immunotherapy, cancer treatment guidelines usually list
hormone therapy as a separate category. However, it can be a form of targeted
therapy. Some cancers depend on hormones to grow. These cancer cells have
receptors on their surface where the hormones attach. Hormone attachment
triggers other events that cause cancer growth. There are two approaches to
using this dependence on hormones to treat cancer. The first involves lowering
hormone levels to starve the cancer. The second is a targeted therapy to block
the hormone receptor. This prevents the cancer from using the hormones it
needs.
Targeted therapy is a treatment option for many types of cancers.
Targeted therapy will not work for all cancers. Your doctor
will need to run tests to find out if your cancer is likely to respond. These
tests will look for molecular markers, gene mutations, and other factors. When
any of these are present, targeted therapy may be an option. Some of the more
common cancers that may respond to targeted therapies include:
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Basal cell skin cancer (the most common type)
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Breast cancer
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Cervical and ovarian cancers
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Colorectal cancer
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Leukemia, lymphoma, and other blood cancers
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Lung cancer
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Melanoma
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Thyroid cancer
Targeted
therapy is an area of tremendous growth for cancer treatment. There are a wide
variety of targeted therapies on the market and many more in clinical trials.
Researchers continue to identify and study useful targets for cancer
treatments.