Why gene mutations are such an important piece of the breast cancer puzzle

By ASTRAZENECA

This article is a part of Studio/B’s Breast Cancer Explored series, exploring the state of breast cancer in 2020 through stories from survivors, loved ones, doctors, and researchers.

Thanks to advances in breast cancer research, we know a lot more about the disease than ever before. Newer, targeted treatment options are available. There is also greater understanding of the role that gene mutations play in helping doctors make informed treatment decisions, and why early detection is essential. Unfortunately, since the start of COVID-19 there has been a large drop in breast cancer screenings and diagnosis. This is concerning given that breast cancer remains the second leading cause of death among women.

A recent study published in the Journal of Clinical Oncology found that breast cancer screenings dropped 89.2% between April of this year and April 2019, with a 47.7% decrease in diagnoses for the same time period. The study suggests this steep decline may lead to a future increase in patients with later-stage cancer, which has lower survival rates. Just one-third of women with metastatic breast cancer (MBC)—the most advanced stage of breast cancer, where the cancer has spread beyond the breast and lymph nodes to other organs or tissues in the body—will be alive five years after diagnosis. It is estimated that there will be more than 168,000 women living with MBC in the U.S. in 2020.

Given these alarming statistics, it’s vital to understand how genetics and testing for gene mutations fit into the overall picture of breast cancer risk and management. Even during COVID-19, people who have a higher risk of breast cancer due to their family history should talk with their doctor about maintaining regular screenings. And for those diagnosed with breast cancer, testing for mutations can help physicians to determine what types of treatments might be appropriate for their specific type of cancer.

How genetics play a role

A woman’s risk of breast cancer nearly doubles if she has a first-degree relative (mother, sister, daughter) who has been diagnosed with breast cancer. Approximately 5%-10% of breast cancer cases are hereditary, resulting from gene mutations passed down from a parent, and there are a number of different genetic mutations that are linked to an increased risk. The most common cause of hereditary breast cancer is an inherited mutation in the BRCA1 or BRCA2 gene.

Another gene associated with breast cancer is the human epidermal growth factor receptor 2 (HER2) gene. Breast cancer cells with higher than normal levels of HER2 are called HER2-positive. Approximately 20% of people diagnosed with metastatic breast cancer are considered to be HER2-positive. The HER2 gene makes the HER2 protein (also called “receptors”), which is found in higher numbers on cancer cells and is important for tumor cell growth. When too many HER2 receptors develop, breast cancer cells may grow more rapidly.

Breast cancer is typically treated with various combinations of surgery, radiation, chemotherapy, hormone therapy, or targeted therapy. The main goal in treating advanced or metastatic breast cancer is to help prevent or slow the progression of the disease while monitoring for treatment-related side effects. Determining the presence of gene mutations and stage of diagnosis can help guide treatment options.

Importance of getting tested

There are two broad categories of tests depending on whether a person wants to know their risk of breast cancer or if they’ve already been diagnosed with the disease and are seeking more information that could help guide their treatment journey. Genetic testing can determine if a person carries a germline (inherited) gene mutation that may increase their risk for breast cancer, while a type of test called biomarker testing can determine whether a person with breast cancer has somatic (acquired) mutations located only in their tumor.

Genetic testing involves a blood or saliva test that uses DNA to identify inherited mutations. Biomarker testing, which can be done as early as diagnosis, involves testing a sample of tissue from the tumor to determine the presence of mutations. Biomarker testing is also sometimes performed by testing non-solid tissue, usually blood, for mutations that may be present in tumor cells or tumor DNA.

Biomarker testing is a powerful tool that can help oncologists determine how to treat a specific type of cancer. For example, studies have found that patients with HER2-positive breast cancer eventually experience a return of their cancer after their initial treatment. Knowing a patient’s HER2 status based on biomarker testing can help their doctor create a treatment plan.

Targeted treatments are changing the landscape

These targeted treatments are designed to target specific genes and mutations that are involved in the growth and survival of specific cancer cells, though they may impact healthy cells as well. During the last year, new treatment options have been approved by the US Food and Drug Administration (FDA) for patients with metastatic breast cancer, and additional studies are in the pipeline across multiple mutation types.

Despite challenges caused by COVID-19, it’s important for people to speak to their doctor promptly about any concerns, especially if they experience new or troubling symptoms. Early detection can have a significant impact on how cancer is managed, and it is important for people to continue scheduling medical check-ups, screenings, and tests. People who have been diagnosed with metastatic breast cancer and caregivers can find resources to help them during their breast cancer journey at http://www.mymbcstory.com.