A DECADE OF INITIAL EXPERIENCE IN ADMINISTRATION OF METAIODOBENZYLGUANIDINE THERAPY FOR ADVANCED STAGE PARAGANGLIOMA AND PHEOCHROMOCYTOMA

Abstract

INTRODUCTION/BACKGROUND
Metaiodobenzylguanidine (MIBG) labeled with radioactive iodine can be utilised for imaging and therapy in advanced stage paraganglioma and pheochromocytoma. Our centre became a local pioneer and started to offer MIBG therapy in 2013. Patients received 200 mCi of Iodine-131 MIBG for each therapy session. We present a case series to highlight the clinical complexity of these rare endocrine neoplasms and our early experience with MIBG therapy.

CASE
The first case involves a 57-year-old male with a large, right pheochromocytoma diagnosed in 2013. Recurrence was noted post-debulking surgery and chemoembolisation. He had 2 MIBG therapies between 2015 and 2016. Surveillance showed a stable underlying tumour and decreasing urine metanephrine level. However, he developed a metastatic pleural nodule and multiple abdominal nodes in 2021. The third MIBG therapy was given in October 2022. Stable disease was noted on a follow-up MIBG scan in April 2023 with markedly decreasing serum Chromogranin A (CgA). For the second case, a 74-year-old male diagnosed with retroperitoneal paraganglioma in 2002 underwent surgery but presented back with metastatic lesions involving the liver and right ilium in 2012. He received 3 cycles of MIBG therapy between 2015 and 2017. Unfortunately, he deteriorated over the subsequent 18 months due to progressive multiple liver, abdominal nodes, lungs and skeletal metastases. The third case is a 50-year-old male with subhepatic paraganglioma diagnosed in 2017. Transarterial embolisations were done as surgery was deemed infeasible. He had 3 MIBG therapies between 2018 and 2020. Surveillance in 2021 showed a stable, focal upper abdomen lesion and decreasing CgA level. However, he developed metastatic disease progression with rebound CgA elevation in February 2022. Fourth MIBG therapy was given in September 2022. A MIBG-avid subhepatic mass was seen with extensive skeletal and cervical, thoracic and abdominal node metastases.

CONCLUSION
MIBG therapy may offer potential palliative benefit in pheochromocytoma and paraganglioma as seen among cases with a solitary large lesion or oligometastasis. However, advanced stage diseases especially those with bone metastasis show a poorer prognosis.