ABCSG 61 / TEODOR: First center opened for patient enrollment
30.07.2025The new ABCSG study ABCSG 61 / TEODOR (Neoadjuvant TrEatment Optimization driven by ctDNA and endOcrine Responsiveness) has launched with the activation of its first site – the Center for Breast Health in the Department of Gynecology at the Medical University of Vienna, headed by Prof. Christian Singer.
TEODOR is dedicated to optimizing neoadjuvant treatment for patients with estrogen receptor-positive, HER2-negative early or locally advanced breast cancer. The trial will investigate whether patients in this subgroup, characterized by no detectable ctDNA in their blood and endocrine responsiveness after 3 weeks of aromatase inhibitor therapy, may benefit from a higher quality of life when receiving endocrine therapy as compared to chemotherapy.
At the start of the study, the ctDNA status of all potential participants is assessed centrally in blood samples, using the Signatera™ test by Natera. After three weeks of treatment with an aromatase inhibitor during the initial run-in phase, the Ki-67 value is measured locally to assess endocrine response.
Participants without detectable ctDNA and a Ki-67 value of ≤10%are randomized in a 2:1 ratio to either receive neoadjuvant endocrine therapy or chemotherapy as per standard of care. Patients who are ctDNA-positive or whose Ki-67 value exceeds 10% after 3 weeks of aromatase inhibitors are assigned to a third study arm receiving chemotherapy.
This national phase II study will include 14 sites across Austria and aims to enroll a total of 256 patients. Following the approximately 8-10 months treatment phase, all participants will be monitored for five years. The study is coordinated by Prof. Michael Gnant, Medical University Vienna and Dr. Daniel Egle, Medical University Innsbruck.
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