New targeted radiation therapy shows near-complete response in rare sarcoma patients

Reston, VA (September 17, 2025)—A novel targeted radiation approach for a rare form of malignant tumor—the solitary fibrous tumor (SFT)—has shown significant success, achieving a near-complete response in three patients. The therapy significantly reduced cancer activity and provided symptom relief, underscoring its potential as a viable treatment option. This research was published in the September issue of The Journal of Nuclear Medicine.

SFT is a rare type of soft tissue tumor with few treatment options available. Although most SFTs are classified as benign with minimal risk of recurrence, about 15 to 20 percent are malignant, and those considered benign have the potential for malignant transformation. For patients with malignant disease, treatment options are scarce, and outcomes are often poor.

"In several sarcomas, particularly SFT, fibroblast activation protein (FAP) is highly expressed on the surface of tumor cells and surrounding fibroblasts,"  said Helena Lanzafame, MD, researcher in the Department of Nuclear Medicine at University Hospital Essen in Essen, Germany. "We sought to deliver radiation therapy directly to the FAP target with the novel radioligand therapy, ⁹⁰Y-FAPI-46."

The study included three patients who had already tried multiple standard therapies without success. Molecular analysis of their tumor tissues revealed remarkably high levels of the FAP protein, confirmed with advanced FAPI-46 PET imaging. Patients received four cycles of ⁹⁰Y-FAPI-46 therapy and their treatment response was evaluated with ¹⁸F-FDG and ⁶⁸Ga-FAPI-46 PET/CT.

Imaging revealed that all patients experienced tumor shrinkage or disease stabilization, as well as significant relief from symptoms, such as severe fatigue and abdominal pain. In addition, no serious side effects were observed among the patients.

"This is the first time we have seen such strong and deep responses in advanced SFT using this precision radiation approach,"  noted Rainer Hamacher, MD, lead oncologist in the Department of Medical Oncology, Sarcoma Center, West German Cancer Center at University Hospital Essen. "Our findings suggest that screening for FAP expression could help identify patients most likely to benefit from this novel therapy."

The team emphasizes that these are early results from a small number of carefully selected patients. Larger prospective clinical trials are needed to confirm the therapy s safety and effectiveness, and to understand how best to integrate it into existing treatment strategies.

The authors of ⁹⁰Y-FAPI-46 Theranostics Leads to Near-Complete Metabolic Response in 3 Patients with Solitary Fibrous Tumors include Helena Lanzafame, Kim Magaly Pabst, Pedro Fragoso Costa, Michael Nader, Stephan Leyser, and Wolfgang Peter Fendler, Department of Nuclear Medicine, West German Cancer Center, University Hospital Essen, Essen, Germany, and German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany; Christoph E. Heilig, Simon Kreutzfeldt, and Stefan Fr hling, Division of Translational Medical Oncology, German Cancer Research Center, Heidelberg, Germany, National Center for Tumor Diseases Heidelberg, a partnership between German Cancer Research Center and Heidelberg University Hospital, Heidelberg, Germany, and German Cancer Consortium, Core Center Heidelberg, Heidelberg, Germany; Eva Wardelmann and Sebastian M hl, Gerhard-Domagk-Institute of Pathology, University of M nster, M nster, Germany; M lanie Desaulniers, Department of Nuclear Medicine, West German Cancer Center, University Hospital Essen, Essen, Germany, German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany, and Department of Nuclear Medicine and Radiobiology, Universit de Sherbrooke, Sherbrooke, Quebec, Canada; Ilektra Antonia Mavroeidi, Ina Pretzell, and Rainer Hamacher, German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany, and Department of Medical Oncology, West German Cancer Center, University Hospital Essen, Essen, Germany; Martin Schuler and Sebastian Bauer, German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany, Department of Medical Oncology, West German Cancer Center, University Hospital Essen, Essen, Germany, and National Center for Tumor Diseases West, Essen, Germany; Jens Thomas Siveke, German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany, Department of Medical Oncology, West German Cancer Center, University Hospital Essen, Essen, Germany, Bridge Institute of Experimental Tumor Therapy, West German Cancer Center, University Hospital Essen, Essen, Germany, Division of Solid Tumor Translational Oncology, German Cancer Consortium, Partner Site Essen, Essen, Germany, and German Cancer Research Center, Heidelberg, Germany; Leila Kamkar, Division of Translational Medical Oncology, German Cancer Research Center, Heidelberg, Germany, and National Center for Tumor Diseases Heidelberg, a partnership between German Cancer Research Center and Heidelberg University Hospital, Heidelberg, Germany; and Ken Herrmann, Department of Nuclear Medicine, West German Cancer Center, University Hospital Essen, Essen, Germany, German Cancer Consortium, Partner Site University Hospital Essen, Essen, Germany, and National Center for Tumor Diseases West, Essen, Germany.

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