Phase II Study of Cixutumumab in Combination with Temsirolimus in Pediatric Patients and Young Adults with Recurrent or Refractory Sarcoma: a Report from the Children's Oncology Group

Background: The combined inhibition of insulin-growth factor type 1 receptor (IGF-1R) and the mammalian target of rapamycin (mTOR) has shown activity in preclinical models of pediatric sarcoma and in adult sarcoma patients. We evaluated the activity of the anti-IGF-1R antibody cixutumumab with the mTOR inhibitor temsirolimus in patients with relapsed or refractory Ewing sarcoma, osteosarcoma, rhabdomyosarcoma, and other soft tissue sarcoma, using the recommended dosages from a pediatric phase I trial.

Methods: Cixutumumab 6 mg/kg and temsirolimus 8 mg/m(2) were administered intravenously once weekly in 4-week cycles to patients <30 years. Temsirolimus was escalated to 10 mg/m(2) for subsequent cycles in patients who did not experience unacceptable first-cycle toxicity. A two-stage design was used to identify a response rate <10 or >35% for each tumor-specific cohort. Tumor tissue was analyzed by immunohistochemistry for potential biomarkers of response.

Results: Forty-three evaluable patients received a median of 2 cycles (range 1-7). No objective responses were observed, and 16% of patients were progression-free at 12 weeks. Dose-limiting toxicity was observed in 15 (16%) of 92 cycles. The most common toxicities were mucositis, electrolyte disturbances, and myelosuppression. The majority of patients receiving a second cycle were not eligible for temsirolimus escalation due to first-cycle toxicity. The lack of objective responses precluded correlation with tissue biomarkers.

Conclusions: Despite encouraging preclinical data, the combination of cixutumumab and temsirolimus did not result in objective responses in this phase II trial of pediatric and young adults with recurrent or refractory sarcoma.