Phase II Study Comparing Neoadjuvant Endocrine Therapy and Chemotherapy for Early and Locally Advanced ERHER2- Breast Cancer in Patients with No Detectable Circulating Tumor DNA and Endocrine Response

What this Trial Is About

Researchers are investigating whether neoadjuvant endocrine therapy is at least as effective as neoadjuvant chemotherapy for treating patients with early or locally advanced estrogen receptor-positive and HER2-negative breast cancer who have no detectable circulating tumor DNA ctDNA before treatment and show endocrine responsiveness. This phase II performance study focuses on comparing these treatments effectiveness, measured by the modified preoperative endocrine prognostic index PEPI score at surgery, while also considering quality of life outcomes. Participants first provide blood and tumor samples for ctDNA assessment using the SignateraTM test. They then receive aromatase inhibitor AI therapy for 4 weeks during a Run-in phase, with a tumor biopsy after 3 weeks to evaluate Ki-67 levels. Based on ctDNA results and Ki-67 values, participants are assigned to one of three groups neoadjuvant AI or tamoxifen if AI is not tolerated for responders, or chemotherapy for non-responders. The Main Treatment Phase lasts 6 to 8 months, followed by surgery and a 5-year follow-up period. Throughout the study, participants attend multiple clinic visits for checkups, blood draws for ctDNA monitoring, and questionnaires about quality of life, symptoms, and sexual health. Key assessment points include before treatment start, after 3 weeks of AI therapy, prior to the Main Treatment Phase, mid-therapy, post-treatment, surgery, and annual follow-ups. Some participants receiving adjuvant chemotherapy have an additional visit after completing chemotherapy. The study evaluates several outcomes including PEPI score, residual cancer burden, survival measures, and breast conservation rates.

ABCSG 61 / TEODOR : Neoadjuvant TrEatment Optimization Driven by Circulating Tumor DNA and endOcrine Responsiveness