Background: Acquired ESR1-mut can emerge in up to 50% of ER+/HER2- mBC patients due to the development of resistance and disease progression on prolonged standard-of-care (SOC) endocrine-based therapy. New treatment options targeting ESR1-mut are currently available, and medical guidelines recommend routine blood testing (liquid biopsy) for ESR1-mut at each disease progression after 1L mBC therapy. Cancer Patients Europe (CPE) initiated a 42-question survey to understand patient awareness.
Objective
To assess the level of awareness, understanding, and informational needs regarding new diagnostic tools and biomarker-based treatment decisions for European metastatic breast cancer patients.
 
Methods: The survey was designed by CPE and reviewed and approved by an external advisory board. CPE and its members disseminated the survey in France, Spain, Italy, UK, and Germany between March and May 2024. 
Results: A total of 1,268 respondents completed the survey: UK n=205; Germany n=161; Spain n=237; Italy n=364; and France n=301. In all respondents, we found: 2/3 did not know which biomarkers they were tested for and 75% did not discuss biomarker testing with their oncologists. In addition, 53% were unaware that tumor cells may release DNA into the bloodstream and 60% had no knowledge that liquid biopsy can be used to detect circulating tumor DNA. Almost 30% were not confident about the use of liquid biopsy to test their tumor and 60% did not know that liquid biopsy can provide reliable information about their cancer. In the subgroup of respondents with mBC and a ER+/HER2- profile (43%), we found that 70% were unaware of the role that ESR1-mut plays in mBC. Of them, only 16% were aware of the new drugs that can be used to treat mBC with ESR1-mut. Merely 12% across all 5 countries had been tested for ESR1-mut (23% in Germany, where the drug was already available).  
Conclusions: These survey results show a significant educational gap, especially in patients with ER+/HER2- mBC, where novel therapeutic and diagnostic options are available that could impact the management of their disease. Detection of specific mutations, such as ESR1-mut, is now possible with liquid biopsy, which is less invasive and a more accessible diagnostic tool. Proper patient and tumor genetic profiling and improved patient awareness of novel therapeutic and diagnostic options are necessary to help inform treatment decisions and improve patient outcomes.