New Targeted Radiation Therapy Shows Remarkable Promise in Rare Sarcoma

A novel targeted radiation therapy has achieved a near-complete response in patients with solitary fibrous tumor (SFT), a rare and often difficult-to-treat cancer. The findings, published in the September issue of The Journal of Nuclear Medicine, highlight a potential breakthrough for patients with limited treatment options.

SFT is an uncommon type of soft tissue tumor. While most cases are classified as benign, 15–20 percent are malignant—and even benign tumors can later transform into aggressive forms. For patients with malignant SFT, current therapies are scarce and long-term outcomes are often poor.

Researchers at University Hospital Essen in Germany tested a radioligand therapy called 90Y-FAPI-46, which delivers radiation directly to tumor cells by targeting fibroblast activation protein (FAP). FAP is highly expressed in several sarcomas, including SFT.

“We sought to deliver radiation therapy directly to the FAP target with this novel approach,” said Helena Lanzafame, MD, of the hospital’s Department of Nuclear Medicine.

The study involved three patients whose cancers had progressed despite multiple prior treatments. Molecular testing confirmed high levels of FAP in their tumors, which were then visualized using advanced FAPI-46 PET imaging. Each patient received four cycles of 90Y-FAPI-46 therapy.

Follow-up scans showed that tumors either shrank or stabilized, and patients experienced meaningful relief from debilitating symptoms such as fatigue and abdominal pain. Importantly, no serious side effects were reported.

“This is the first time we have seen such strong and deep responses in advanced SFT using this precision radiation approach,” said Rainer Hamacher, MD, lead oncologist at the West German Cancer Center. “Our findings suggest that screening for FAP expression could help identify patients most likely to benefit.”

While the results are promising, the researchers caution that they are based on a very small patient group. Larger clinical trials are needed to confirm safety, determine long-term outcomes, and define how best to incorporate the therapy into standard treatment plans.