Ppgl Radionuclide Therapy Selection

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name: ppgl-radionuclide-therapy-selection
description: Selects between 131I-MIBG and 177Lu-DOTATATE radionuclide therapy for PPGL based on imaging results. Triggers include PPGL patient requires radionuclide therapy, positive 123I-MIBG scintigraphy indicating MIBG-avid tumor, and positive somatostatin receptor scintigraphy for SSTR-avid tumor.
---

# Radionuclide Therapy Selection for PPGL Based on Imaging Results

## STEP 1 — Gather Information
Collect recent 123I-MIBG scintigraphy and somatostatin receptor scintigraphy reports; confirm PPGL diagnosis via biochemical or pathological criteria; verify patient has unresectable or metastatic PPGL requiring systemic therapy; assess eligibility for radionuclide therapy (adequate marrow function, no pregnancy, access to licensed facility).

## STEP 2 — Rule In / Rule Out
Is the 123I-MIBG scintigraphy positive (avid tracer uptake in PPGL lesions)?  
- **Yes** → Rule in for 131I-MIBG therapy; proceed to Step 4.  
- **No** → Rule out 131I-MIBG; proceed to Step 3.

## STEP 3 — Classify or Stratify
Is the somatostatin receptor scintigraphy positive (avid tracer uptake in PPGL lesions)?  
- **Yes** → Classify as SSTR-avid tumor; proceed to Step 4 for 177Lu-DOTATATE.  
- **No** → Both imaging modalities negative; consider alternative systemic therapies (e.g., CVD chemotherapy) or clinical trial; radionuclide therapy not indicated based on current imaging.

## STEP 4 — Decide
- If 123I-MIBG positive: administer 131I-MIBG therapy per approved dosing (5.55–7.4 GBq IV over 1 hour) with thyroid blockade (potassium iodide) and renal amino acid infusion.  
- If somatostatin receptor scintigraphy positive: administer 177Lu-DOTATATE therapy per approved dosing (7.4 GBq IV over 30 minutes, up to four doses at 8-week intervals) with renal amino acid infusion.  
Document treatment decision and obtain informed consent for radionuclide handling.

## Clinical Guardrails / Mimics / Pitfalls
Do not rely solely on 123I-MIBG scintigraphy in SDHx-related PPGL due to false negatives; avoid 131I-MIBG in pregnancy without thyroid protection; do not omit amino acid infusion for 177Lu-DOTATATE to reduce renal toxicity; false-positive MIBG uptake can occur in normal adrenal glands—correlate with lesion anatomy; ensure therapy is administered in a licensed radionuclide room with radiation safety oversight; do not substitute with non‑insurance‑covered agents (e.g., 68Ga-DOTATATE PET) for treatment selection.

## Concrete Clinical Example
A 52‑year‑old with metastatic PPGL presents with symptomatic liver lesions. 123I-MIBG scintigraphy shows intense uptake in hepatic metastases; somatostatin receptor scintigraphy is negative. Based on positive MIBG scan, 131I-MIBG therapy is selected. Patient receives 7.4 GBq IV 131I-MIBG with potassium iodide blockade and L‑lysine/L‑arginine infusion; post‑treatment scan shows partial response and decreased catecholamines.

**Source:** Japan Endocrine Society Clinical Practice Guideline for the Diagnosis and Management of Pheochromocytoma and Paraganglioma 2025, Japan Endocrine Society, 2025, DOI:10.1507/endocrj.EJ25-0165