On June 22, 2026 Delphi Diagnostics reported the publication of findings from the GEICAM/9906 clinical trial demonstrating that the company’s Endocrine Activity Index (EAI) can identify patients with hormone receptor-positive, HER2-negative (HR+/HER2−) breast cancer who derive meaningful benefit from adjuvant chemotherapy containing weekly paclitaxel.

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The study, published in Clinical Cancer Research, is titled "Sensitivity to endocrine therapy index predicts benefit from weekly adjuvant paclitaxel for hormone receptor-positive breast cancer in the GEICAM/9906 trial," and was conducted by investigators from the GEICAM Spanish Breast Cancer Group and The University of Texas MD Anderson Cancer Center.

This prospective-retrospective analysis independently validated previous findings and further helps to establish EAI as the first genomic assay shown to predict benefit from a contemporary taxane-based chemotherapy regimen in HR+/HER2− breast cancer.

The study evaluated tumor samples and outcomes from patients enrolled in the landmark GEICAM/9906 randomized phase III trial. Investigators found that patients with very low endocrine activity, score of <0.75 as measured by EAI, experienced significantly improved distant recurrence-free outcomes when weekly paclitaxel was added to anthracycline-based chemotherapy. In contrast, patients with higher endocrine activity did not demonstrate additional benefit from paclitaxel treatment.

"This study represents an important milestone for precision oncology and provides independent confirmation that endocrine activity within an HR+/HER2- breast tumor can predict sensitivity to specific chemotherapy approaches," said Federico A. Monzon, MD, Chief Medical Officer at Delphi Diagnostics. "These findings support the potential for EAI to help clinicians personalize treatment decisions and select chemotherapy regimens more likely to benefit individual patients."

The results build upon previous clinical evidence and demonstrate reproducibility across two independent randomized clinical trials. Together, these studies suggest that EAI may provide oncologists with actionable information beyond traditional prognostic tests by helping determine not only whether chemotherapy should be considered, but which chemotherapy strategy is most likely to provide clinical benefit.

"Current genomic assays primarily estimate recurrence risk, but they generally do not predict which specific chemotherapy regimen will be most effective," said Winz Casagrande, Chief Executive Officer, Delphi Diagnostics. "EAI represents a new generation of predictive biomarkers designed to guide treatment selection and help deliver more individualized care for patients with breast cancer."

The GEICAM/9906 analysis showed that approximately 16% of HR+/HER2− tumors exhibited low endocrine activity and were associated with improved outcomes from weekly paclitaxel-containing therapy. The findings support the growing role of biologically informed treatment selection and may help reduce unnecessary exposure to treatments unlikely to provide benefit.

(Press release, Delphi Diagnostics, JUN 22, 2026, View Source [SID1234668881])