Before choosing a therapy, doctors need to know what’s fueling the cancer.
One of the ways to categorize breast cancers is by receptor status. Breast cancer cells often have some type of receptor on the surface, and the type of receptor can determine which treatment is used on the breast cancer.
“There are three possible receptors,” says Amy Tiersten, MD, oncologist and hematologist at Dubin Breast Center, Mount Sinai Hospital in New York City. “There are hormone receptors—estrogen and progesterone—and then there’s a protein called HER2.” Learn more about the types of breast cancer here.
Hormone Therapy for Breast Cancer
Breast cancers with estrogen receptors or progesterone receptors are fueled by the respective hormones; these are called hormone receptor-positive breast cancers. For example, when estrogen binds to an estrogen receptor on a breast cancer cell, it helps the breast cancer grow.
Hormone receptor-positive breast cancer is treated with something called hormone therapy, specifically anti-estrogen therapy (even if the breast cancer cells contain progesterone receptors).
“Anti-estrogen medication plays a very big role in the treatment of [hormone receptor-positive] breast cancer, both in preventing a recurrence [and] treating more advanced disease,” says Dr. Tiersten.
Hormone therapy for breast cancer works by preventing estrogen (or progesterone) from binding to the receptor, which helps shrink or eliminate the tumor. Some types of hormone therapy lower the amount of estrogen. Typically, hormone therapy is done after surgery (such as lumpectomy or mastectomy) to eliminate remaining cancer cells throughout the body.
Targeted Therapy for Breast Cancer
Breast cancers with HER2 receptors are fueled by a growth protein called HER2 (or HER2/neu); this is called HER2-positive breast cancer. For this type of breast cancer, the cancer cells contain abnormally high levels of HER2 on the surface.
HER2-positive breast cancer is treated with targeted therapy. This treatment works by targeting the HER2 protein and blocking the growth of cancer cells.
Targeted therapy for HER2-positive breast cancer works so well that “nowadays, it’s considered a good thing to have HER2-positive breast cancer because we have incredibly effective targeted antibodies to that HER2 protein,” says Dr. Tiersten.
Treatment Options for Triple-Negative Breast Cancer
Some types of breast cancer lack all three of the receptors known to fuel breast cancer growth; these cancers are known as triple-negative breast cancers.
Hormone therapy and targeted therapy are newer and more effective types of breast cancer treatment. Unfortunately, these options don’t work on triple-negative breast cancers since they aren’t affected by estrogen, progesterone, or HER2.
“At the time, all we really have for triple-negative breast cancer is your standard, traditional chemotherapy,” says Dr. Tiersten. Luckily, this type of breast cancer is “very sensitive” to chemotherapy, and this treatment is more effective on triple-negative breast cancer than other types of cancer.
Chemotherapy can be done before surgery (neoadjuvant chemotherapy) or after surgery (adjuvant chemotherapy).
Neoadjuvant chemotherapy is used to shrink down a tumor prior to surgery so that “patients are able to become lumpectomy candidates” instead of having to get a full mastectomy, according to Dr. Tiersten.
Adjuvant chemotherapy is used after surgery (lumpectomy or mastectomy) to ensure all residual cancer cells in the body are eliminated.
“We really used to consider breast cancer one disease, but biology has moved so far forward that we really tailor the treatment to the specific type of breast cancer,” says Dr. Tiersten.
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