Why Aren't There Targeted Therapies for TNBC?
Any diagnosis of breast cancer can be hard to process, but hearing the term “triple-negative breast cancer” can be especially distressing. You may know that other types of breast cancer can be treated with targeted therapies, medicines that can attack just cancer cells rather than all cells. You may wonder why your doctors only offer you chemotherapy.
You may be confused by what you read or hear about triple-negative breast cancer. Different sources may describe the disease or treatments in different ways. Some people think there is little or nothing that can be done for this type of breast cancer. Even the term “triple-negative” sounds scary, like you are being hit three times with bad news.
Triple-negative describes breast cancers that test negative for three receptors found on breast cancer cells: estrogen, progesterone and HER2. These receptors are markers that help control cell functions, such as how they divide, multiply and grow.
When a tumor sample has one or more of the receptors, the cancer is called estrogen receptor-positive, progesterone receptor-positive or HER2-positive, based on the receptors found. If a tumor sample shows no receptors, it’s called triple-negative.
About 15 to 20 percent of cancers are triple-negative, which means they are negative for all three markers. But all triple-negative breast cancers do not behave the same. Knowing whether the breast cancer is positive or negative for these receptors helps decide what kinds of treatment will work well against the cancer.
In the case of hormone receptor-positive and HER2-positive cancers, there are some medicines that target the receptors found on the cancer cells and stop them from growing or kill them.
Because triple-negative breast cancer has none of these receptors, medicines that target them won’t work against the disease. And, so far, no research has found other targets, or biomarkers, in triple-negative breast cancer. A biomarker is a trait that is easy to measure and shows the behavior of a group of cells, whether normal or cancer.
Researchers hope to one day find such targets and design specific targeted therapies to treat it.
Today, triple-negative breast cancer is treated with chemotherapy medicines that generally treat cells that grow abnormally in the body. These medicines, while not targeted therapies, can be effective at treating triple-negative breast cancer.
Researchers are working to improve their understanding of the biology of triple-negative breast cancers, how these types of cancers behave and what puts people at risk for them. Their goals are to find the best ways to use treatments that already exist as well as to figure out new approaches to the disease.
Your doctor may tell you triple-negative breast cancer is “challenging” and “harder to treat” than other types of breast cancer. While it’s true that many triple-negative cancers are aggressive, how well your treatment will work depends on the size of your tumor and whether the cancer has traveled to the lymph nodes or other areas of the body.
Remember that there are treatments available to you. Your provider will help guide you toward the best treatment options for your situation.