Abstract
10060 Background: Neuroblastoma (NB) is the most common solid extra-cranial tumor of childhood. 131I-mIBG is a targeted radiopharmaceutical for patients with advanced NB and is one of the most active agents in this treatment resistant population. To date, no clinically relevant biomarkers of response or toxicity have been reported in patients treated with 131I-mIBG. Methods: Patients with relapsed or refractory NB who received 131I-mIBG at UCSF were eligible to participate in this prospective correlative study. Blood samples were obtained at baseline and 72 hours after 131I-mIBG infusion. We quantified a panel of biomarkers shown to be effected in patients receiving other forms of radiation, including: serum amylase; plasma Flt-3 ligand; plasma monocyte colony stimulating factor (MCSF); and CDKN1A mRNA in mononuclear cells. Extent of modulation of each marker was evaluated using paired t-tests at hour 0 and 72. We assessed potential differential modulation between groups based on response (PR/CR vs SD/PD), toxicity (grade 3 non-hematologic toxicity; grade 4 neutropenia or thrombocytopenia) or administration of combination therapy (131I-mIBG alone vs in combination with vincristine/irinotecan or vorinostat) using unpaired t-tests. Results: 26 patients (21 male; median age 7 years) participated and received a median 131I-mIBG dose of 18 mCi/kg. 16 patients received 131I-mIBG in combination. We observed robust modulation of amylase (median fold increase from baseline 3.1; p <0.0001), Flt-3 ligand (median fold increase from baseline 3.6; p=0.0005), and CDKN1A mRNA (median fold decrease from baseline 4.3, p=0.0002). No differences were noted in MCSF (p=0.80). Patients receiving combination 131I-mIBG had more robust modulation of Flt-3 ligand (mean difference 296 pg/mL; p=0.02) compared to single agent 131I-mIBG. No correlations with clinical response or toxicity were found. Conclusions: Amylase, Flt-3 ligand, and CDKN1A mRNA all show robust modulation after 131I-mIBG treatment. Patients receiving 131I-mIBG in combination demonstrated the largest changes in plasma Flt-3 ligand. In this initial analysis, no associations were found between response or toxicity and the proposed biomarkers.
Published Version
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