[177Lu]Lu-PSMA extravasation: from quantitative imaging to clinical guidelines

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Therapy
• Medical Physics

Background:

• Extravasation of therapeutic radioligands like [177Lu]Lu-PSMA-617 can cause localized radiation injury.
• Current management strategies for radioligand extravasation lack standardization and are often empirical.

Purpose of the Study:

• To evaluate [177Lu]Lu-PSMA extravasation using automated, time-resolved dosimetry.
• To support evidence-based conservative management of radioligand extravasation.

Main Methods:

• Two patients with [177Lu]Lu-PSMA extravasation received conservative treatment (massage, warmth, elevation).
• Quantitative SPECT/CT imaging assessed clearance kinetics with early and delayed scans.
• Automated workflow included deep learning segmentation, partial volume correction, Monte Carlo dosimetry, and kinetic modeling.

Main Results:

• Both patients showed rapid clearance of extravasated activity (effective half-lives ~1.5 h).
• Highest absorbed doses in sub-volumes (<1 mL) were below necrosis thresholds (<10 Gy).
• Systemic dosimetry, including renal doses, was largely unaffected by extravasation events.

Conclusions:

• Conservative management of [177Lu]Lu-PSMA extravasation is effective, with rapid clearance and doses below deterministic injury thresholds.
• Automated quantitative dosimetry provides objective data for timely clinical decisions.
• This approach facilitates the development of standardized management protocols for radioligand extravasation.