(P 454) TREATMENT PATTERNS AND OUTCOMES IN RADIATION-INDUCED SARCOMA: FIRST RESULTS OF THE TETRIS-PROJECT - A MULTIMODAL RETROSPECTIVE ANALYSIS FROM A TERTIARY CENTER

Author(s)

Melissa Harbrücker, MD (she/her/hers)

Resident
Sarcoma Unit, Department of Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University
Mannheim, Baden-Wurttemberg, Germany

Co-Author(s)

MH

Madelaine Hettler, MD

Sarcoma unit, Department of Surgery, University Medical Center and Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
Mannheim, Baden-Wurttemberg, Germany
Franka Menge, MD

Dr.
Sarcoma Unit, Department of Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University
Mannheim, Baden-Wurttemberg, Germany
PH

Peter Hohenberger, N/A, MD

Sarcoma Unit, Department of Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University
Mannheim, Baden-Wurttemberg, Germany
CR

Christoph Reissfelder, MD

Department of Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University
Mannheim, Baden-Wurttemberg, Germany
Bernd Kasper, MD, PhD (he/him/his)

Medical Director Mannheim Cancer Center (MCC)
Mannheim University Medical Center, University of Heidelberg
Mannheim, Baden-Wurttemberg, Germany
UK

Ulrich Kneser, MD

Department of Hand, Plastic and Reconstructive Surgery, Microsurgery, Burn Trauma Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, 67071 Germany.
Ludwigshafen, Rheinland-Pfalz, Germany
FS

Felix Strübing, MD

Department of Hand, Plastic and Reconstructive Surgery, Microsurgery, Burn Trauma Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, 67071 Germany.
Ludwigshafen, Rheinland-Pfalz, Germany
GM

Gina Mackert, MD

Department of Hand, Plastic and Reconstructive Surgery, Microsurgery, Burn Trauma Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, 67071 Germany.
Ludwigshafen, Rheinland-Pfalz, Germany
SB

Sylvia Büttner, Dr.

University of Heidelberg, Mannheim University Medical Center, Medical Statistics, Biomathematics and Information Processing, Mannheim, Germany.
Mannheim, Baden-Wurttemberg, Germany
MR

Mattea Reinisch, MD

Department of Gynecology and Obstetrics, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
Mannheim, Baden-Wurttemberg, Germany
CB

Christoph Brochhausen, MD

Institute of Pathology, University Medical Center Mannheim, Medical Faculty Mannheim, University Heidelberg, Mannheim, Germany
Mannheim, Baden-Wurttemberg, Germany
MW

Markus Wartenberg, n/a

Deutsche Sarkom-Stiftung (DSS) / German Sarcoma Foundation, patient support.
Wölfersheim (Södel), Hessen, Germany
KA

Karin Arndt, n/a

Deutsche Sarkom-Stiftung (DSS) / German Sarcoma Foundation, patient support.
Wölfersheim, Hessen, Germany
Jens Jakob, MD (he/him/his)

Consultant Sarcoma Surgeon
Sarcoma Unit, Department of Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University
Mannheim, Baden-Wurttemberg, Germany
Stefan Fröhling, M.D. (he/him/his)

Division Head
German Cancer Research Center
Heidelberg, Baden-Wurttemberg, Germany

Objective: This study presents the first results of the "TumorEcoSystems in Radiation-Induced Sarcoma (TETRIS)-project, funded by the DKFZ-Hector Foundation, which aims to establish an integrated clinical and translational research framework for radiation-induced sarcomas (RIS). RIS are rare, high-grade malignancies arising as a late complication of radiotherapy. Their management is clinically challenging due to prior treatment burden, anatomical constraints, and poor prognosis. This study aimed to characterize treatment strategies and assess outcomes in RIS patients treated at a certified sarcoma center.

Methods: We retrospectively analyzed RIS patients treated at the Sarcoma Center Mannheim, Germany. Patient records were reviewed for treatment modalities including across up to five therapy lines. Key data included intervention types, timing, and time to recurrence or progression. Response was quantified in months from therapy initiation to disease recurrence. Subgroup analyses were performed for patients treated at our certified sarcoma center.

Results: Notably, 92 % of patients were initially treated outside of certified centers. 60 RIS patients were analyzed, with 89.9% having a history of breast cancer. Radiation-induced angiosarcoma was the most common histological subtype (75.4%). The median latency was 9.2 years. Among RIS patients, initial surgical treatment was performed in 91.4% of cases. First-line chemotherapy was administered in 8.6% of patients, primarily with anthracycline-based regimens. Time to progression after first-line therapy ranged from 1 to 32 months (mean 8.1, SD 7.9). In the subgroup treated at our center (n = 29), 62% received neoadjuvant chemotherapy, while 38% underwent primary surgery. Second-line treatments included repeat resections and taxane-based chemotherapy. Mean response duration dropped to 5.3 months in second-line therapy. Only three durable remissions were observed beyond the second line.

Conclusion: Neoadjuvant chemotherapy combined with surgery showed more favorable outcomes in our center compared to surgery elsewhere. These results underscore the need for early referral to specialized centers and highlight that simple surgical excision in breast centers without sarcoma expertise and without initiation of multimodal therapy remains a major burden in RIS therapy. The TETRIS project aims to provide insights into molecular mechanisms of RIS, develop translational therapeutic approaches and includes patient participation in focus groups.

Initial Treatment Patterns Radiation-Induced Sarcoma
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