HOUSTON, Texas, June 22, 2026
Delphi Diagnostics has announced the publication of new clinical findings validating the predictive power of its Endocrine Activity Index® (EAI™) in identifying patients with hormone receptor-positive, HER2-negative (HR+/HER2−) breast cancer who are most likely to benefit from weekly paclitaxel-based adjuvant chemotherapy. The study, published in Clinical Cancer Research, analyzed data from the landmark GEICAM/9906 Phase III clinical trial and demonstrated that EAI can identify a distinct subset of patients who experience significantly improved outcomes when treated with weekly paclitaxel in combination with anthracycline-based chemotherapy. The findings represent an important advancement in precision oncology, helping establish EAI as the first genomic assay shown to predict benefit from a contemporary taxane-based chemotherapy regimen in HR+/HER2− breast cancer. As oncology increasingly shifts toward personalized treatment approaches, the study highlights the growing value of predictive biomarkers capable of guiding chemotherapy selection and optimizing patient outcomes.
Phase III Trial Analysis Confirms Predictive Value of EAI
The newly published analysis was conducted by investigators from the GEICAM Spanish Breast Cancer Group and The University of Texas MD Anderson Cancer Center using tumor samples and clinical outcomes from patients enrolled in the randomized Phase III GEICAM/9906 trial. Researchers found that patients exhibiting very low endocrine activity, defined as an EAI score below 0.75, experienced significantly improved distant recurrence-free survival when weekly paclitaxel was added to anthracycline-based chemotherapy. In contrast, patients with higher endocrine activity did not derive a meaningful additional benefit from paclitaxel treatment.
Importantly, the study independently validated previous clinical findings and demonstrated reproducibility across separate randomized trials, strengthening confidence in EAI as a clinically relevant predictive biomarker. Approximately 16% of HR+/HER2− breast tumors were identified as having low endocrine activity, representing a patient population that may particularly benefit from paclitaxel-containing treatment strategies.
Advancing Precision Oncology Through Biomarker-Guided Treatment
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Current genomic tests used in breast cancer management primarily focus on estimating recurrence risk and determining whether chemotherapy should be considered. However, they generally provide limited information regarding which specific chemotherapy regimen may deliver the greatest clinical benefit. The Endocrine Activity Index aims to address this gap by measuring endocrine activity within a tumor and identifying biological characteristics associated with chemotherapy sensitivity. According to the study findings, EAI offers clinicians a more refined approach to treatment selection by helping determine not only whether chemotherapy is appropriate but also which therapeutic strategy may be most effective for an individual patient.
This approach aligns with the broader movement toward personalized medicine, where treatment decisions are increasingly guided by molecular and genomic characteristics rather than traditional clinical factors alone. By identifying patients most likely to respond to weekly paclitaxel, EAI has the potential to improve outcomes while reducing unnecessary exposure to treatments that may offer limited benefit.
Expanding Opportunities for Individualized Breast Cancer Care
The publication further strengthens the clinical evidence supporting Delphi Diagnostics’ strategy of developing predictive tools that guide personalized breast cancer treatment. The company’s proprietary EAI test measures endocrine activity in stage II and stage III HR+/HER2− breast cancer and has demonstrated value as both a prognostic and predictive biomarker across multiple studies. Beyond estimating long-term recurrence risk, the assay provides actionable information regarding responsiveness to dose-intense taxane-based chemotherapy regimens. As precision oncology continues to evolve, technologies capable of matching patients with the most effective therapies are expected to play an increasingly important role in clinical decision-making.
The latest findings suggest that EAI may help oncologists optimize treatment planning, improve therapeutic outcomes, and support more individualized care strategies for breast cancer patients. With validation from a major Phase III clinical trial and publication in a leading oncology journal, EAI is emerging as a promising tool for advancing biomarker-driven cancer treatment.
Source: Delphi Diagnostics press release
