Clinical Significance of Persistent Tumor in Bone Marrow during Treatment of High-risk Neuroblastoma

The records of 63 high-risk neuroblastoma patients with bone marrow (BM) tumors at diagnosis were retrospectively reviewed. All patients received nine cycles of induction chemotherapy followed by tandem high-dose chemotherapy and autologous stem cell transplantation (HDCT/auto-SCT). Follow-up BM examination was performed every three cycles during induction chemotherapy and every three months for one year after the second HDCT/auto-SCT. BM tumor cells persisted in 48.4%, 37.7%, 23.3%, and 20.4% of patients after three, six, and nine cycles of induction chemotherapy and three months after the second HDCT/auto-SCT, respectively. There was no difference in progression-free survival (PFS) rate between patients with persistent BM tumor and those without during the induction treatment. However, after tandem HDCT/auto-SCT, the PFS rate was worse in patients with persistent BM tumor than in those without (probability of 5-yr PFS 14.7% ± 13.4% vs. 64.2% ± 8.3%, P = 0.009). Persistent BM tumor during induction treatment is not associated with a worse prognosis when intensive tandem HDCT/auto-SCT is given as consolidation treatment. However, persistent BM tumor after tandem HDCT/auto-SCT is associated with a worse prognosis. Therefore, further treatment might be needed in patients with persistent BM tumor after tandem HDCT/auto-SCT.