Lesion-level Quantitative Post-therapy SPECT/CT During <sup>177</sup>Lu-DOTATATE PRRT for NET Liver Metastases.
Quantitative SPECT/CT metrics like kBq/ml max and SUVmax may correlate with volumetric changes in liver metastases during PRRT, but the small sample size limits the conclusions.
Where it sits
this study against the rest of the octreotide corpusSummary and findings
This study assessed lesion-level changes in quantitative indices during 177Lu-DOTATATE PRRT in 12 patients with neuroendocrine tumors (NETs) and liver metastases. Significant reductions in kBq/ml max and SUVmax were observed from baseline to final evaluation. The study aimed to correlate these changes with CT-based volumetric assessments.
Abstract
<h4>Background/aim</h4>Quantitative post-therapy single-photon emission computed tomography/computed tomography (SPECT/CT) may offer valuable insights for response assessment during peptide receptor radionuclide therapy (PRRT), but lesion-level evidence for liver metastases from neuroendocrine tumors (NETs) remains limited. This study assessed lesion-level longitudinal changes in practical quantitative indices, including kBq/ml max and maximum standardized uptake value (SUVmax), during <sup>177</sup>Lu-DOTATATE PRRT and their association with CT-based volumetric change.<h4>Patients and methods</h4>This retrospective single-center study included 12 patients with NETs (51 liver metastases) treated with <sup>177</sup>Lu-DOTATATE PRRT. Quantitative SPECT/CT was performed the day after each cycle. SUVmax and kBq/ml max were measured for each lesion, and tumor volume was assessed using the CT component. Baseline (post-cycle 1) and final-cycle values were recorded. Lesions were classified as non-progressive (shrinkage/disappearance/stable) or progressive based on CT volumetric change. Spearman's rank correlation, the Wilcoxon signed-rank test, and the Mann-Whitney <i>U</i>-test were used.<h4>Results</h4>Eleven patients completed four cycles and one discontinued after three cycles. Lesion volume, kBq/ml max, and SUVmax significantly decreased from baseline to final evaluation (all <i>p</i><0.01). Of 51 lesions, 39 were non-progressive and 12 were progressive. Percentage reductions in kBq/ml max and SUVmax were strongly correlated with volumetric shrinkage (ρ=0.757 and 0.734). Non-progressive lesions showed greater reductions in both indices than progressive lesions (both <i>p</i><0.01). Baseline kBq/ml max and SUVmax were higher in non-progressive lesions (<i>p</i>=0.029 and 0.030).<h4>Conclusion</h4>In this exploratory lesion-level analysis for NET liver metastases, post-therapy quantitative SPECT/CT metrics (kBq/ml max and SUVmax) were associated with CT-based volumetric change during <sup>177</sup>Lu-DOTATATE PRRT.
Background
This paper addresses the assessment of response to peptide receptor radionuclide therapy (PRRT) using quantitative post-therapy SPECT/CT in patients with liver metastases from neuroendocrine tumors (NETs). Prior studies have indicated the potential of SPECT/CT in evaluating treatment response, but lesion-level evidence remains limited. Understanding these metrics could enhance the evaluation of treatment efficacy in this patient population.
Methods
This retrospective single-center study included 12 patients with NETs, encompassing 51 liver metastases treated with 177Lu-DOTATATE PRRT. Quantitative SPECT/CT was performed the day after each treatment cycle, with SUVmax and kBq/ml max measured for each lesion. The study recorded baseline (post-cycle 1) and final-cycle values, classifying lesions based on CT volumetric change.
Results
Lesion volume, kBq/ml max, and SUVmax significantly decreased from baseline to final evaluation (all p<0.01). Of the 51 lesions, 39 were classified as non-progressive and 12 as progressive. The percentage reductions in kBq/ml max and SUVmax were strongly correlated with volumetric shrinkage (ρ=0.757 and 0.734). Non-progressive lesions exhibited greater reductions in both indices compared to progressive lesions (both p<0.01).
Interpretation
The findings suggest that quantitative SPECT/CT metrics may provide valuable insights into treatment response during PRRT for NET liver metastases. While the statistical significance of the results is clear, the clinical significance remains uncertain due to the small sample size and the exploratory nature of the study. The correlation between imaging metrics and volumetric change is noteworthy but requires further validation in larger cohorts.
Key findings
- Lesion volume, kBq/ml max, and SUVmax significantly decreased from baseline to final evaluation (all p<0.01).
- Of 51 lesions, 39 were classified as non-progressive and 12 as progressive.
- Percentage reductions in kBq/ml max and SUVmax were strongly correlated with volumetric shrinkage (ρ=0.757 and 0.734).
- Non-progressive lesions showed greater reductions in both kBq/ml max and SUVmax than progressive lesions (both p<0.01).
- Baseline kBq/ml max and SUVmax were higher in non-progressive lesions (p=0.029 and 0.030).
Limitations
- small sample size of n=12
- retrospective single-center design
- no long-term follow-up reported
- exploratory nature of the analysis