Stable disease and improved health-related quality of life (HRQoL) following fractionated low dose 131I-metaiodobenzylguanidine (MIBG) therapy in metastatic paediatric paraganglioma: observation on false "reverse" discordance during pre-therapy work up and its implication for patient selection for high dose targeted therapy.

The incidence of paraganglioma in the paediatric population is exceedingly rare, accounting for < 0.1% of childhood cancers. We report here the response and toxicity profile in a case of malignant paraganglioma which was treated with what is currently perceived as an unconventional and non-standard approach, using three consecutive low doses of 131I-MIBG (a cumulative dose of 11 647.6 MBq). The patient had a stable disease at the end of 42 months follow-up following the first treatment with 131I-MIBG. Excellent symptomatic and hormonal responses were observed. The only adverse effect was mild nausea in the first 24 h after therapy. In addition to the potentially primary end point of radiological and biochemical response measurement, we, in this paper, endeavoured to look for a quality of life evaluation for this form of treatment. Given the rarity of this condition, the experience gained by this therapeutic approach is intriguing from response and toxicity standpoints and may be extrapolated to malignant pheochromocytoma as well. An apparent "reverse discordance" between 131I-MIBG scintigraphy and 99Tc(m)-MDP bone scan encountered during pre-therapy work up is also described with possible explanations. This draws attention to an important clinical issue in selecting patients for high dose targeted therapy.