Phase II trial of irinotecan in children with relapsed or refractory rhabdomyosarcoma: A joint study of the French Society of Pediatric Oncology and the United Kingdom Children's Cancer Study Group

Purpose: This phase II study was designed to evaluate the efficacy of irinotecan administered intravenously once every 3 weeks in pediatric patients with recurrent or refractory rhabdomyosarcoma. Patients and Methods: A total of 35 patients younger than age 20 years, with refractory or relapsed rhabdomyosarcoma for which standard treatments have failed, received irinotecan at 600 mg/m² administered as a 60-minute infusion every 3 weeks. Concomitant treatments included atropine for cholinergic symptoms, loperamide for diarrhea at the first liquid stool, and preventive antiemetic treatment. Tumor response was assessed every two cycles until progression according to WHO criteria. Results: The best overall response rate to irinotecan was 11.4% (95% CI, 3.2 to 26.7%; 2.9% complete responses, 8.5% partial responses) from all patients recruited. The median times to progression and survival were 1.4 and 5.8 months, respectively. A total of 112 cycles were administered, with a median number of two cycles per patient (range, 1 to 16). The most common grade 3/4 toxicities were neutropenia (46%), abdominal pain or cramping (17%), cholinergic syndrome (14%), nausea/vomiting (11%), anemia (11%), thrombocytopenia (9%), and diarrhea (6%). Conclusion: In heavily pretreated children with a high tumor burden who have been treated with multi-agent chemotherapy, irinotecan administered intravenously as a single agent, at 600 mg/m² every 3 weeks, showed an interesting objective response rate and a good tolerance profile in rhabdomyosarcoma.