Double‐conditioning regimen consisting of high‐dose thiotepa and melphalan with autologous stem cell rescue for high‐risk pediatric solid tumors: A second report

BACKGROUND: Pediatric patients with high-risk, relapsed, or refractory solid tumors have a poor prognosis. We have previously reported a dose-finding experience of high-dose chemotherapy consisting of thiotepa and melphalan ("double-conditioning regimen"). Using doses derived from that study, we have treated patients since 2005. We now report a retrospective review of patients treated by this fixed dose. PROCEDURE: We reviewed 50 patients (median 4 years; range 0-15 years) with high-risk or relapsed/refractory solid tumors treated by this dose-fixed, double-conditioning regimen from April 2005 to May 2014. Doses were thiotepa 800 mg/m2 and melphalan 280 mg/m2 for children ≥2 years of age, and 32 mg/kg and 6 mg/kg, respectively, for children <2 years of age. Further, doses were reduced according to creatinine clearance with poor renal function. RESULTS: Nonhematological toxicity was mainly gastrointestinal-grade 3 mucositis (n = 41) and grade 3-4 diarrhea (n = 10). Neurological, renal, and endothelial cell toxicity and sinusoidal obstruction syndrome were not observed. There were two toxic deaths (interstitial viral pneumonia). This regimen demonstrated antitumor activity against several types of tumors. Although the frequency of gastrointestinal toxicity was high, other severe toxicity was not observed. CONCLUSIONS: Our double-conditioning regimen was very well tolerated and demonstrated antitumor activity. We are moving forward with multi-institutional trials now.