New Research Highlights Risks of Biomarker-Based Tests in Breast Cancer Treatment Decisions

In a recent examination by the German Institute for Quality and Efficiency in Health Care (IQWiG), the implications of biomarker-based tests in guiding adjuvant chemotherapy decisions for breast cancer patients have been critically evaluated. The study, released in July 2025, focuses on patients diagnosed with first-time, hormone receptor-positive, and HER2/neu-negative breast cancer. The report specifically addresses the risks associated with using these tests, particularly in premenopausal women aged 50 and under.

The analysis arose after the Federal Joint Committee (G-BA) tasked IQWiG with assessing the efficacy of biomarker tests in determining treatment pathways for breast cancer patients. The agency's findings indicate that for premenopausal women, utilizing tests like MammaPrint and Oncotype DX might lead to significant undertreatment due to a lack of supporting evidence for their effectiveness in this demographic.

"The risk of mistakenly forgoing chemotherapy on the basis of a biomarker-based test is therefore substantially higher in premenopausal than in postmenopausal breast cancer patients," stated Daniel Fleer, Deputy Head of IQWiG's Non-Drug Interventions Department. The study highlights that while postmenopausal women may benefit from tests like Oncotype DX, as corroborated by randomized controlled trials (RCTs), the same cannot be said for their younger counterparts.

According to the preliminary report, released in June 2024, and subsequently revised based on feedback, the evidence supporting the use of biomarker tests in premenopausal women remains insufficient. The IQWiG's findings are aligned with previous studies, such as the MINDACT study for MammaPrint and the TAILORx study for Oncotype DX, which provided valuable insight for postmenopausal women but failed to deliver adequate data for younger patients.

The implications of these findings are significant, as the use of these tests has been widely adopted in outpatient care, often leading to decisions that could adversely affect patient outcomes. The German statutory health insurance currently covers four biomarker tests, including MammaPrint and Oncotype DX, in clinical settings where patients' lymph nodes are not yet affected by cancer.

The report calls for a reevaluation of treatment protocols, emphasizing the need for a more personalized approach to breast cancer therapy. Experts suggest that clinical characteristics and patient-specific factors should take precedence over biomarker test results in premenopausal women, advocating for a balanced consideration of both biological markers and individual patient circumstances.

In a broader context, this study reflects a growing trend in oncology where precision medicine is being scrutinized for its efficacy in various populations. The challenges of integrating biomarker testing into clinical practice underline the necessity for ongoing research and a critical assessment of current methodologies. As the field of oncology evolves, the need for guidelines that are both evidence-based and tailored to specific patient demographics becomes increasingly apparent.

In conclusion, as the healthcare landscape continues to adapt to advancements in cancer treatment, the findings from IQWiG serve as a crucial reminder of the complexities involved in making treatment decisions. Policymakers and healthcare providers must prioritize robust, evidence-based approaches to ensure optimal outcomes for all breast cancer patients, particularly those in vulnerable demographics. Further research is essential to clarify the roles of biomarker testing in the nuanced landscape of breast cancer treatment, ensuring that all patients receive the best possible care based on sound clinical evidence.