MIBG scores: A means of identifiying an ultra-high risk group of patients

Objectives Treatment of neuroblastoma ranges from tumoral resection alone (Stage 1) to aggressive protocols involving resection following chemotherapy, with subsequent bone marrow transplant (BMT) and adjuvant biotherapy (Stage 4). We sought to determine if MIBG scan scores could be used to identify an ultra-high risk group of patients (pts) that might benefit from alternatives to standard Stage 4 therapies.

Methods Newly diagnosed, Stage 4 neuroblastoma pts enrolled on Children’s Oncology Group protocol A3973 who were MIBG positive at diagnosis (DX: 280 pts) were evaluated with MIBG scans at the end of induction therapy(EOI: 274 pts), post BMT(PBMT; 203 pts), and post biotherapy(PBT; 99 pts). These MIBG scans were analyzed using the Curie score(CS) which is calculated by summing the evaluation of 10 body sites. Using the Youden index, optimal cut-off points were determined to differentiate pts who did and did not have events impacting survival (EFS) and to assess overall survival (OS). A cut-off score of 5 at EOI was also examined as it was comparable to the optimum value and diverted approximately 15% of high-risk pts with EFS of 10% to the high risk group.

Results The optimal cut-off Curie scores were 9, 2, 0, and 0 for DX, EOI, PBM and PBT, respectively. The results of MIBG scans at EOI appear to identify high risk neuroblastoma pts who are at greater risk for an event or death. The EOI CS appears to be more useful in identifying MYCN amplified pts at greater risk for an event of death than for non-MYCN amplified pts. The prognostic ability of the CS (< / =5 vs.>5) was determined to be most relevant to the identification of a post-induction ultra high risk subset of pts.

Conclusions End of induction MIBG scores can successfully identify an ultra high risk subset of pts with poor prognosis. Identification of such pts may allow changes to and/or institution of alternative therapies that may improve overall prognosis or quality of life