Decitabine (DAC) in combination with doxorubicin (DOX) and cyclophosphamide (CTX) in relapsed neuroblastoma (NBL): A Children's Oncology Group Study

Abstract

9565 Background: Loss of caspase-8 expression causes resistance to apoptosis-inducing agents and potentiates metastasis in NBL. In vitro treatment of NBL cell lines with DAC results in increased caspase-8 expression and enhanced apoptosis following exposure to DOX. As a component of a pediatric phase 1 study, we evaluated low-dose DAC with DOX and CTX in a cohort of children with relapsed NBL. Promoter specific DNA methylation in peripheral blood mononuclear cells (PBMC) was studied. Methods: Patients received a 1-hour infusion of DAC, 5 mg/m2, daily on days 0–6, followed on day 7 by 45 mg/m2 of DOX (with dexrazoxane) and 1 g/m2 of CTX. All patients received G-CSF. Cycles were repeated every 28 days. Methylation-specific and quantitative PCR were used to measure promoter-specific DNA methylation in PBMC prior to and after DAC (day 7 and day 28). Results: Twelve patients with recurrent NBL (median age 9 years, 10 males) were enrolled. DAC/DOX/CTX was well tolerated with grade 4 myelosuppression being the predominant toxicity. Grade 4 neutropenia, median 11 days duration, occurred in 10 pts and grade 4 thrombocytopenia, median 10 days, in 7 patients. Eight patients had progressive disease after = 2 courses of therapy. The remaining 4 patients had stable disease with 5 to 8 courses. Methylation and subsequent demethylation (40–90% decreased methylation) of the MAGE-1 promoter was detected before and after DAC respectively, in PBMC from 6 of 9 patients analyzed to date. Re-expression of MAGE-1 mRNA was also demonstrated in post treatment samples. Caspase-8 demethylation was not detected in PBMC; nor was hypermethylation of caspase-8 detected in pre-treatment PBMC, possibly due to low tumor burden in blood. Conclusions: DAC in combination with cytotoxic chemotherapy was relatively well tolerated in heavily pre-treated children with relapsed NBL. Low-dose DAC induces demethylation and re-expression of MAGE-1 in PBMC, and may be a potential surrogate marker of demethylation within tumor cells. The use of low dose DAC in combination with other agents warrants further study in NBL. No significant financial relationships to disclose.