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Receiving a breast cancer diagnosis can be overwhelming. Not
only is it an emotional experience, you're also likely to receive a lot of
information all at once. Trying to understand the explanation of your diagnosis
(and the medical jargon that comes along with it) may feel like learning a
foreign language, but by breaking down the diagnosis and treatment process,
you’ll soon become fluent.
The First Step: Determining Your Breast Cancer Type
To choose the best treatment, your doctor needs to identify
key factors about your specific type of breast cancer. A number of important
tests will be performed in the beginning to accomplish this. Some will be used
to determine the size of the tumor and whether the cancer has spread to your
lymph nodes or other parts of your body. Based on these test results, your
cancer will be given a stage from I to IV.
Other tests look at the cancer cells themselves. Under a
microscope, tumor cells are studied to check for the presence of proteins
called hormone receptors (HR) and human epidermal growth factor receptor 2
(HER2). This helps your doctor understand how your cancer cells grow and
therefore provides a road map for how to fight them. If your cancer cells do
have hormone receptors, your cancer is considered hormone receptor-positive
(HR+); if few or no hormone receptors are seen, it is considered hormone receptor-negative
(HR-) If you have an excess number of HER2 receptors, your cancer is considered
HER2-positive (HER2+); conversely, if few or no HER2 receptors are found, your
cancer will be called HER2-negative (HER2-).
The most common type of breast cancer is HR+/HER2-. About
70% of all breast cancers fall into this category.
Understanding the Role of Hormone Receptors and HER2
Hormone receptors respond to the reproductive hormones,
estrogen and progesterone. When these hormones attach to the cancer cells, they
signal the cancer cell to grow. If your cancer is HR+, your doctor may indicate
which specific hormone receptors are present: estrogen receptor-positive (ER+),
progesterone receptor-positive (PR+), or both (ER+/PR+).
HER2 protein receptors are found on all breast cells; they
play a role in how breast cells grow. However, some breast cancer cells have
too many HER2 receptors, making the cells divide too rapidly. As a result, this
type of cancer can grow and spread quickly. Around 25% of breast cancers are
HER2+.
Treating HR+/HER2- Breast Cancer
If you have HR+/HER2- breast cancer, you will likely first receive
some traditional forms of cancer treatment: surgery, chemotherapy, and
radiation. Surgery is performed to try and remove the cancer, either by
removing the tumor, the whole breast, and/or any affected lymph nodes. Strong
beams of radiation may be directed at the affected area in an attempt to kill
the cancer cells. Powerful chemotherapy drugs may be given to destroy the
cancer cells and try and prevent it from returning.
Additionally, due to the presence of hormone receptors, a
special kind of treatment known as hormone therapy may be used to keep the cancer
from growing or spreading. These drugs block the hormones from attaching to the
receptors on the cancer cells; they can also decrease the amount of estrogen in
the body. Some common forms of hormone therapy include the following:
-
Selective
estrogen receptor modulators (SERMs): the most frequently used SERM is
called tamoxifen (Soltamox, Nolvadex). These drugs prevent estrogen from acting
on the cancer cells. -
Luteinizing
hormone-releasing hormone (LHRH) analogs: drugs such as goserelin (Zoladex)
and leuprolide (Lupron) are used in pre-menopausal women to stop their ovaries
from producing estrogen. Some women have surgery to remove their ovaries
completely. -
Aromatase
inhibitors: medications such as anastrozole (Arimidex), letrozole (Femara)
and exemestane (Aromasin) are used in post-menopausal women. They stop estrogen
from being produced in areas of body other than the ovaries. -
Certain types of targeted therapy may also be used for
HR+/HER2- breast cancer, especially when the cancer metastasizes. This form of
treatment attacks the cancer cells, but leaves normal cells alone. Some
targeted therapies improve the effectiveness of chemotherapy and hormone
therapy. -
CDK4/6
inhibitors: these drugs target the cyclin-dependent kinase (CDK) proteins
within the cell. This stops breast cancer cells from dividing. Palbociclib
(Ibrance) and ribociclib (Kisqali) are two examples. -
Everolimus
(Afinitor): this targeted therapy is used for post-menopausal women and
blocks a protein known as mTOR. This makes it hard for the breast cancer cells
to grow and divide. It may also stop the tumor from creating new blood vessels.
Other forms of targeted therapy exist for treating breast
cancer, such as trastuzumab (Herceptin), pertuzumab (Perjeta), and lapatinib
(Tykerb), but they are used for HER2+ cancer. These medications will not be
effective in HER2- cancer due to the lack of HER2 receptors to target.
Educate Yourself
Breast cancer research and treatment has come a long way.
The more we understand about the cancer cells themselves, the better we can
develop methods to fight them. As a breast cancer patient, it is important for
you to have a good understanding of your particular type of breast cancer. This
will help you recognize what treatment options are available to you so you can
make informed decisions about your medical care. Be sure to ask your doctor if
you have any questions regarding your diagnosis.