Speaker
Description
Background:
Neuroblastoma is a paediatric solid tumour of the sympathetic nervous system, with high-risk disease typically corresponding to advanced-stage (stage 3–4). Activity administration is guided by body weight, with an initial activity of 444 MBq/kg, while the second cycle is adjusted to a cumulative whole-body absorbed dose of 4 Gy. Despite standardised regimens, absorbed doses to tumour lesions and critical organs vary substantially among, and hematological toxicity remains dose-limiting, often requiring supportive care prior to stem cell transplantation.
Methods:
The study retrospectively analyzed 23 patients (14 males, 9 females; median age 3.7 years, range 1–27) treated with two cycles of [¹³¹I]I-mIBG. Whole-body absorbed dose was estimated from serial dose-rate measurements, with the second cycle calculated to reach a cumulative 4 Gy. Post-therapy lesion-based dosimetry was not routinely feasible due to patient age and clinical constraints. Whole-body dose may overestimate red marrow exposure due to radiotracer accumulation in tumour lesions. Planar scintigraphy was available in a limited subset for approximate red marrow dose estimation. Hematological parameters and transfusion requirements were monitored and correlated with dose and clinical response.
Results:
All patients reached the target cumulative whole-body absorbed dose, with a median of 3.9 Gy (range 1.2–5.3 Gy). Hematological toxicity varied substantially; almost all patients required platelet transfusions prior to stem cell transplantation. Among 23 patients, 16 showed partial or complete tumour regression, 3 demonstrated stable disease and 4 experienced progression. Whole-body dose did not consistently correlate with clinical response.
Conclusion:
The current standardised [¹³¹I]I-mIBG regimen achieves the target cumulative whole-body absorbed dose but shows variable in hematological toxicity and heterogeneous responses. Given stem cell transplantation and supportive transfusions, there may be scope to increase administered activity to improve therapeutic effect without exceeding tolerable hematological toxicity.