Sirolimus in Combination With Metronomic Chemotherapy in Children With High-Risk Solid Tumors

Sirolimus, also known as rapamycin, is a potent immunosuppressive drug. Due to its profound immunosuppressive actions, sirolimus was initially developed and received regulatory approval for the indication of prevention of allograft rejection following solid organ transplant. Sirolimus also possesses anti-tumor activity through its anti-proliferative effect, by the inhibition of translation of key messenger ribonucleic acids (mRNAs) into proteins required for cell cycle progression from the G1 to the S phase. Palliative care with the use of antiangiogenic metronomic chemotherapy in the form of low-dose daily oral administration of etoposide and cyclophosphamide in combination with antiangiogenic agents such as celecoxib, is feasible and well-tolerated in children with refractory solid tumors Sirolimus is used orally in adults and children for the prevention of allograft rejection following solid organ transplant. The Pediatric Preclinical Testing Program (PPTP) performed testing of sirolimus as a single agent against an in vitro panel of pediatric cell lines, as well as against in vivo pediatric tumor panels. Sirolimus exhibited variable inhibition of cell line growth, ranging from 19% to 85% (median 49%). This study has three cohorts: a prospective cohort of patients with high-risk extracranial solid tumor, a prospective cohort of patients with recurrent solid tumors (any histology) in second complete remission, and a historical control cohort of patients matched on diagnosis, age, metastatic site, and date of diagnosis. The matched historical controls will be obtained from the same treating institution as the corresponding case to account for institutional differences in treatment and supportive care. The primary objective of the study is to improve the 2-year progression-free survival in children with high-risk solid tumors who are administered a maintenance regimen with continuous sirolimus administered on a backbone of metronomic chemotherapy following the completion of "standard" therapy, as compared to high-risk solid tumor patients treated with observation alone following completion of "standard" therapy.