Early Molecular Response of Marrow Disease to Biologic Therapy Is Highly Prognostic in Neuroblastoma

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Abstract
Purpose: A promising treatment strategy for stage 4 neuroblastoma patients is the repeated application of anti-GD2 immunotherapy after activating myeloid effectors with granulocyte-macrophage colony-stimulating factor (GM-CSF). To use early marrow response as a prognostic marker is particularly relevant for patients not likely to benefit from this therapy. Patients and Methods: Eighty-six stage 4 neuroblastoma patients older than 1 year at diagnosis were classified in four clinical groups on protocol entry: complete remission or very good partial remission (n = 33), primary refractory (n = 33), secondary refractory (n = 10), and progressive disease (n = 10). Bone marrow samples collected before and following treatment were assayed for GD2 synthase mRNA by real-time reverse transcriptase polymerase chain reaction. Response and survival analyses were performed on posttreatment samples before the third cycle at 1.8 months from protocol entry. Results: GD2 synthase mRNA was evident in pretreatment marrow samples of the four clinical groups (42%, 52%, 60%, and 80% of samples, respectively), with median transcript level of 10.0, 16.6, 26.5, and 87.2, respectively. This marker became negative following antibody plus GM-CSF in 77% of complete remission or very good partial remission, 45% of primary refractory, 25% of secondary refractory, and 0% of progressive disease group. Progression-free survival was statistically different between responder and nonresponder groups (P < .0001). Among patients with minimal residual disease, molecular responders had a significantly lower risk of disease progression at a median follow-up of 29.8 months (P = .0001). Conclusion: GD2 synthase mRNA is a sensitive response marker of neuroblastoma in the bone marrow. It is particularly useful for minimal residual disease evaluation and may potentially be useful as an early predictor of resistance to antibody plus GM-CSF immunotherapy.