Supplementary Material for: New insights from long-term clinical use of ctDNA-based minimal residual disease monitoring in translocation-associated sarcomas

Introduction: Assessment of circulating tumor DNA (ctDNA) as means to monitor disease activity in translocation-associated tumors has become very popular in clinical practice. However, there are still few studies on its clinical application to date. Our study evaluates the clinical applicability of ctDNA as a biomarker for monitoring minimal residual disease (MRD) in patients with translocation-associated sarcomas. Methods: In this retrospective study, we correlated 285 ctDNA samples from 34 patients diagnosed with translocation-associated sarcoma with the clinical course and images. Blood samples were collected at multiple time points during follow-up (median: 97 weeks, range: 7–398). Results: We discovered a significant association between ctDNA levels and the clinical course of the disease, particularly noting differences between patients in remission or with progressive disease (p = 0.001). Furthermore, although we noted that ctDNA levels remained undetectable in a few cases of unilocular recurrence (n = 3), they were consistently higher in patients with multilocular recurrence (n = 14; p = 0.008). Conclusion: Monitoring ctDNA levels provides highly specific, additional information enabling early recurrence detection in patients with translocation-associated sarcomas during the follow-up and can be integrated into clinical practice. However, MRD monitoring by ctDNA quantification alone does not allow the reliably detection of 100% of unilocular recurrences and should be complemented by the use of conventional imaging techniques.