The ESR1 control kit that is helping labs get it right

ESR1 mutations play a crucial role in breast cancer progression and resistance to hormone therapy, making their detection vital for treatment decisions. As clinical laboratories strive for accuracy in ESR1 testing, the need for reliable controls is more pressing than ever. The ZeptoMetrix ESR1 Control Kit is designed to meet this need, providing a comprehensive quality control solution for PCR and NGS based ESR1 assays.

To understand the importance of ESR1 controls in clinical practice, we spoke with Dr. Karsten Kleo, a research assistant at Charité – Universitätsmedizin Berlin, Institute of Pathology. His laboratory is a medium-sized molecular diagnostics lab specializing in the analysis of biomarkers for cancer diseases. His team focuses on genetic testing for ESR1 mutations using digital PCR, a method critical for identifying low-frequency mutations linked to therapy resistance.

ESR1 mutations and their clinical significance

ESR1 mutations are predominantly found in the ligand-binding domain (LBD) of the estrogen receptor alpha (ERα). Mutations such as Y537S and D538G render the receptor constitutively active, meaning it continues to drive estrogen-related cell growth even in the absence of estrogen. This leads to resistance against hormone therapies like aromatase inhibitors, which are designed to suppress ERα activity.

These mutations are especially prevalent in metastatic hormone receptor-positive (HR+) breast cancer. Studies indicate that up to 20–40% of HR+ metastatic breast cancer patients develop ESR1 mutations after prolonged exposure to hormone therapies. Detecting these mutations early can help guide treatment decisions, such as switching to selective estrogen receptor degraders (SERDs) or combination therapies tailored to hormone-resistant tumors.

“The complexity lies primarily in the accurate detection of the numerous possible ESR1 mutations,” Kleo notes. “Another challenge is detecting mutations in the low-frequency range.” This underscores the importance of reliable quality controls in ensuring test accuracy.

Ensuring accuracy with the ZeptoMetrix ESR1 Control Kit

The ZeptoMetrix ESR1 Control Kit provides a standardized solution for clinical labs conducting ESR1 testing. Designed for use with both PCR- and NGS-based assays, the Kit includes 16 common ESR1 mutations, covering key variants like Y537S and D538G. This extensive mutation panel allows laboratories to validate their assays comprehensively, ensuring reliable detection of even rare ESR1 mutations.

Kleo's team used the ZeptoMetrix ESR1 control in their lab to support assay development and quality control. “It was initially relevant for the development of our ESR1 assay, particularly for detecting low-frequency mutations with an allele frequency of 0.1–1%,” he explains. “Additionally, it served as a quality control to ensure the reliability and reproducibility of our assay.”

Notably, the Kit has also streamlined the lab’s workflow. “It has reduced the error rate and optimized data interpretability,” Kleo notes. He emphasizes that integrating the Kit into their workflow was straightforward since it is fully compatible with existing PCR technologies.

He further adds it was particularly useful in his lab due to its high reproducibility and reliability. “Compared to other control kits, ZeptoMetrix offers a higher concentration of ESR1 WT DNA, which is important for performing dilution series, especially during the establishment phase,” he explains.

High-quality controls are crucial

Controls are essential in molecular diagnostics to verify assay performance and prevent false positives or negatives. In ESR1 mutation testing, which directly impacts treatment decisions, using high-quality controls is particularly critical.

Without reliable reference materials, labs risk inconsistent results, which can mislead oncologists when making treatment choices. The ZeptoMetrix ESR1 Control Kit helps mitigate this risk by offering a well-characterized, reproducible control that allows laboratories to test assay sensitivity and specificity under consistent conditions.

“Testing the detection limits of such an assay can be very challenging,” Kleo emphasizes. “The ZeptoMetrix ESR1 oncology control allowed us to test the limits of our assay, which can be difficult when relying solely on real-life samples, as these are often scarce, and their DNA concentration may not always allow for extensive analyses.”

This ability to assess assay performance even at low allele frequencies is a key advantage. “All detections were successfully carried out, and the dilution to 0.1 AF worked perfectly. Even at this low concentration, detection in digital PCR was still reliable,” Kleo confirms.

Flexibility for multiple applications

The ZeptoMetrix ESR1 Control Kit is designed for versatility, making it an invaluable tool for various laboratory applications, including:

• Running routine controls for PCR- and NGS-based ESR1 assays
• Verification and validation of ESR1 test methods
• Use as reference material for assay development
• Spike-in experiments to evaluate assay performance in different conditions

By including a broad range of clinically significant ESR1 mutations, the Kit provides comprehensive coverage, helping labs ensure their assays can detect all relevant mutations with confidence.

Advancing precision in breast cancer testing

As ESR1 testing advances, reliable oncology controls are essential for driving progress in breast cancer diagnostics. The ZeptoMetrix ESR1 Control Kit supports this effort by providing a mutation-rich reference that enhances assay validation and quality control. “In routine samples with weak signals, it helps classify data more accurately and reduce false positives,” Kleo notes. By improving the precision of ESR1 mutation detection, the Kit contributes to more reliable testing – an important step in refining breast cancer diagnostics and treatment strategies.

For Kleo’s lab, the Kit has proven to be an indispensable tool. “The Kit includes the common ESR1 hotspot mutations, making it a dependable and precise control kit that we highly recommend!” he concluded.

By enabling accurate and reproducible ESR1 mutation detection, ZeptoMetrix is helping clinical laboratories deliver reliable results that directly impact patient care. Whether for routine quality control or assay development, the ZeptoMetrix ESR1 Control Kit is a trusted solution for ensuring precision in breast cancer diagnostics.

Find out how the ZeptoMetrix ESR1 Control Kit can advance your breast cancer testing.