Understanding Metastatic Breast Cancer (MBC)

Sponsored by: Beyond Pink: Sharing our Metastatic Breast Cancer Story, a program brought to you by AstraZeneca

When people think of breast cancer, they tend to think of pink ribbons and fundraising walks. The power of pink has inspired women to rethink what a diagnosis of breast cancer means. That inspiration, coupled with scientific advancements, has led to increased survival from breast cancer, primarily due to earlier detection through screening and greater awareness. However, for the nearly 151,000 women in the United States living with a diagnosis of metastatic breast cancer (MBC) — which means the cancer has spread to other areas of the body outside of the breast – early detection and awareness of early-stage breast cancer is not enough. For these women and their families, there is a gap in information or education to help support their disease journey.

Living with MBC differs greatly from coping with an early-stage breast cancer diagnosis because women with the disease will remain in treatment for the rest of their lives, so the need for continued education, support and awareness must be tailored to their specific needs.

“An important factor to help determine a course of treatment for a patient diagnosed with MBC is knowing the tumor’s hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status,” said Dr Julie Gralow, Director of Breast Medical Oncology at Seattle Cancer Care Alliance. “Understanding the connection between MBC and the tumor’s HR and HER2 status can help those living with MBC to more effectively partner with their healthcare provider to manage the disease. This knowledge not only provides a better understanding of treatment options and tests for those living with MBC, but it can also empower them to participate in the decision-making process.”

MBC and the Hormone Connection

Since breast cancer can be hormone driven — and the progression of MBC can be directly related to the types of hormones and how they communicate with the tumor tissue – it is extremely important to know the tumor’s HR status. When patients are first diagnosed with MBC, the doctor will order tests to determine if the tumor is HR positive or negative. The most common types of hormone receptors are estrogen (ER) and progesterone receptors (PR). If the test is positive for either receptor type, the cancer is classified as HR positive. If neither is determined to be positive, the cancer is classified as HR negative. Roughly 66 percent of breast cancers are considered HR positive, meaning that the growth of the tumor is fueled by female hormones – either estrogen or progesterone.

While not defined as a hormone, HER2 status is also often used as another type of classification for MBC cells. MBC patients are tested for HER2, a gene that can also have an impact on the growth of breast cancer tumors. In a healthy cell, the HER2 gene functions normally and contains a normal amount of HER2 receptors, which helps control the growth of healthy breast cells. When the HER2 gene does not function properly, this results in too many HER2 receptors, which causes the cancer cell to divide and grow more rapidly. This is called HER2 positive (HER2+) MBC.

Some MBC cells are neither ER, PR nor HER2 positive, so they are referred to as Triple Negative MBC cells. Triple Negative MBC occurs when the tumor tests negative for estrogen, progesterone and HER2 receptors. In this case, cancer growth is not supported by hormones nor by the presence of too many HER2 receptors. It is also important to periodically re-biopsy the tumor because it can change over time, which can have an impact on the treatment recommendations and decisions.

MBC Education Can Empower Patients to Participate in Treatment Decisions

Knowing the type of MBC, including the tumor’s HR status and HER2 status, can help patients to more actively participate in treatment decisions that aim to delay or stop the growth of the tumor. Patients with HR positive tumors may have choices among the available hormone therapies. The goal of this type of therapy is to reduce the amount of estrogen, block the estrogen receptor and/or work to destroy the estrogen receptor.

If the tumor is classified as HER2 positive or triple negative, a doctor may recommend a different type of treatment specific to each type of MBC. As the understanding of breast cancer continues to evolve, researchers are working to identify additional genes and receptors that may lead to the development of new treatment options. Because different hormones and proteins can impact cancer tumors in many ways, treatment may require various approaches to best manage the disease.

“Knowing the tumor’s HR status and HER2 type is critical to determining a plan of action that best fits each individual,” said Dr Gralow. “Having the knowledge of what drives tumor growth ultimately allows women living with MBC the opportunity to more actively manage their care.”

Because of the chronic nature of the disease, an MBC diagnosis can be overwhelming and cause feelings of isolation for those living with the disease. To help patients better understand MBC and empower them to be more active in treatment decisions, AstraZeneca has launched Beyond Pink: Sharing our Metastatic Breast Cancer Story, which provides education and resources for their unique journey.