Pre-treatment ¹¹¹In-pentetreotide SPECT/CT vs. baseline ¹⁷⁷Lu-DOTATATE SPECT/CT: are there differences in lesion...

Area of Science:

• Nuclear Medicine
• Oncology
• Radiology

Background:

• 111In-pentetreotide imaging is used for pre-treatment screening in peptide receptor radionuclide therapy (PRRT) where SSTR-PET tracers are unavailable.
• 177Lu-DOTATATE imaging post-first PRRT cycle serves as a baseline for response assessment.
• Differences between these somatostatin receptor (SSTR) scans have not been reported.

Purpose of the Study:

• To compare 111In-pentetreotide and 177Lu-DOTATATE imaging in neuroendocrine tumor (NET) patients.
• To evaluate differences in lesion detection and uptake between the two SSTR imaging tracers.
• To assess the implications for pre-treatment evaluation in PRRT.

Main Methods:

• Retrospective, single-center study of NET patients undergoing PRRT.
• Analysis of planar and SPECT/CT imaging (111In-pentetreotide pre-treatment, 177Lu-DOTATATE post-first cycle).
• Comparison of lesion counts (Krenning score ≥2) and quantitative uptake (SUVmax, T/B ratio) using Wilcoxon signed-rank test.

Main Results:

• 177Lu-DOTATATE detected significantly more lesions than 111In-pentetreotide on both planar and SPECT/CT (p<0.05).
• Lesion uptake was significantly higher with 177Lu-DOTATATE (SUVmax and T/B ratios, p<0.001).
• Sub-centimeter lesions were primarily responsible for increased detection with 177Lu-DOTATATE SPECT/CT.

Conclusions:

• Baseline 177Lu-DOTATATE imaging shows superior lesion detection and higher uptake compared to pre-treatment 111In-pentetreotide imaging.
• Careful interpretation of baseline 177Lu-DOTATATE scans is crucial to avoid misinterpreting increased lesion detection as disease progression.
• 111In-pentetreotide screening may underestimate treatable lesions, emphasizing the need for SSTR PET in pre-treatment evaluation.