Pazopanib shows promise as Ewing’s sarcoma treatment

Researchers report success in using pazopanib to treat young patients diagnosed with deadly Ewing’s sarcoma.

They published their findings on Oct. 23, 2025 in Frontiers in Oncology

As background, the authors noted that Ewing sarcoma is one of the most common bone cancers seen in children. Prior research has shown that less than a quarter of children with multi-metastatic Ewing sarcoma survived five years after their diagnosis.

The authors said, “Despite the use of different treatment regimens, patients with primary multi-metastatic Ewing sarcoma disease have a dismal outcome. Lately, pazopanib has been proposed as an effective salvage regimen for soft tissue sarcoma (STS), including extraosseous Ewing sarcoma (ESS). Thus, we sought to evaluate this approach for young patients with primary multimetastatic bone Ewing sarcoma.”

“Pazopanib is a pill that blocks the tumor’s ability to grow new blood vessels, which tumors need to survive and spread,” added Prof Anna Raciborska of the Warsaw Mother and Child Institute. “By cutting off this ‘blood supply, the drug presumably makes tumors weaker and more sensitive to chemotherapy and radiation. This may slow down the disease and help existing treatments work better.”

Pazopanib was originally developed for the treatment of renal cell carcinoma.

The investigators enrolled 11 subjects with primary multi-metastatic bone Ewing sarcoma (metastasis to the bone and/or bone marrow).

The subjects were 5-11 years-old when they initiated treatment with pazopanib. They took pazopanib during and after their chemotherapy.

Pazopanib treatment was paused for surgery, and it was stopped if the disease progressed or a subject experienced unacceptable side effects.

On average, the patients took pazopanib for 1.7 years.

Five of the 11 subjects had surgery on their primary tumor.  Three subjects received stem cell transplants and 10 underwent radiotherapy.

Imaging revealed that all but one of the subjects responded to pazopanib treatment.

One patient (9.1%) suffered disease progress. Two patients suffered relapse (18.2%), and one patient died (9.1%). Ten patients (90.9%) are currently alive, with a median follow-up of 2.6 years (range 1.2 to 9.2 years).

The estimated 2-year event-free survival and overall survival for the whole group were 68.2% and 85.7%, respectively.

“Although combining cancer treatments carries a risk of increasing the treatment toxicity, pazopanib was also very well tolerated, with minimal, treatable side-effects,” the authors said.

The authors concluded, “Pazopanib was well-tolerated in young patients, even when it was administered with chemotherapy and radiation therapy together. Pazopanib turned out to be effective in patients with primary multi-metastatic Ewing sarcoma and particularly could be considered as an option for them. ”

Raciborska added, ““While we wait for new treatment options, it is possible to implement this existing drug to improve outcomes in very high-risk patients. It opens the door to targeted therapies earlier in the disease course, potentially improving survival and quality of life.”