Post-PRRT scans: which scans to make and what to look for

Area of Science:

• Nuclear Medicine
• Oncology
• Radiology

Background:

• Peptide receptor radionuclide therapy (PRRT) is a standard treatment for metastatic neuroendocrine tumors (NET).
• Post-therapy imaging is crucial for monitoring treatment response and disease progression.
• Current imaging protocols involve both planar imaging and SPECT/CT, potentially increasing patient burden.

Purpose of the Study:

• To evaluate the clinical utility of SPECT/CT and the added value of planar imaging in post-PRRT assessment.
• To simplify imaging protocols and reduce patient burden.
• To identify prognostic indicators from imaging findings.

Main Methods:

• 100 patients with metastatic NET undergoing PRRT were included.
• Post-therapy imaging included whole-body planar imaging and SPECT/CT (abdomen/thorax) 24 hours after each cycle.
• Images were assessed for new lesions, discordant findings, lesion location, and additional CT findings.

Main Results:

• SPECT/CT identified abdominal and/or thoracic disease in 55 patients.
• 16 patients had bone lesions only visible on planar imaging (out of SPECT/CT range).
• Additional CT findings, particularly ascites, were associated with significantly poorer overall survival (13.2 vs. 37.9 months).

Conclusions:

• Thoracoabdominal SPECT/CT is the preferred post-PRRT imaging modality, with planar imaging showing no added benefit in this cohort.
• Abdominal SPECT/CT may suffice for patients with abdominal disease only.
• Reviewing CT for additional findings, especially ascites, is critical for prognostic assessment.