MRD to identify no evidence of disease status in advanced breast cancer with CR.

e13034 Background: Although advanced breast cancer remains to be considered as uncurable, an increasing number of patients achieved long-term complete remission. How to accurately assess the disease remission status after treatment for advanced breast cancer helps subsequent treatment. We aim to evaluate the molecular residual disease detection in metastatic breast cancer patients who achieved complete clinical remission and assess its prognostic significance. Methods: This cross-sectional study included 33 recurrent or metastatic breast cancer patients who achieved clinical complete response between June-December 2023. A comprehensive next-generation sequencing analysis of plasma-derived circulating tumor DNA was performed. The primary endpoint was to assess molecular residual disease status in advanced breast cancer patients who achieved complete metabolic response on PET-CT imaging. The secondary endpoint was to characterize the genomic mutation profile of CR patients. Results: In the cohort of 33 advanced breast cancer patients who achieved complete metabolic response on PET-CT, 93.9% maintained disease-free status for more than 12 months after combination therapy. Circulating tumor DNA (ctDNA) remained detectable in 33.3% of these patients despite clinical remission. Human epidermal growth factor receptor 2 (HER2)-positive patients demonstrated a higher propensity for recurrence, predominantly presenting with central nervous system metastases. Patients with undetectable ctDNA showed significantly improved overall survival compared to those with detectable ctDNA (P = 0.046). Conclusions: This study demonstrates that achieving No Evidence of Disease (NED) status is an attainable goal in advanced breast cancer treatment and correlates with improved survival outcomes. The findings highlight the clinical utility of ctDNA monitoring and emphasize the importance of intensive surveillance in HER2-positive patients. While the results support the feasibility of long-term disease control in advanced breast cancer, they also underscore the critical need for risk-stratified follow-up strategies. Clinical trial information: ChiCTR2300071524 .