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A Practical Guide for the Production and PET/CT Imaging of 68Ga-DOTATATE for Neuroendocrine Tumors in Daily Clinical Practice
Published on: April 17, 2019
Treatment-related changes in neuroendocrine tumors as assessed by textural features derived from 68Ga-DOTATOC PET/MRI
Manuel Weber1, Lukas Kessler2, Benedikt Schaarschmidt3
1Department of Nuclear Medicine, University Hospital Essen, University of Duisburg-Essen, Essen, Germany. manuel.weber@uk-essen.de.
Background:
Neuroendocrine tumors (NETs) frequently overexpress somatostatin receptors (SSTRs), which is the molecular basis for 68Ga-DOTATOC positron-emission tomography (PET) and radiopeptide therapy (PRRT). However, SSTR expression fluctuates and can be subject to treatment-related changes. The aim of this retrospective study was to assess, which changes in PET and apparent diffusion coefficient (ADC) occur for different treatments and if pre-therapeutic 68Ga-DOTATOC-PET/MRI was able to predict treatment response to PRRT.
Methods:
Patients with histopathologically confirmed NET, at least one liver metastasis > 1 cm and at least two 68Ga-DOTATOC-PET/MRI including ADC maps were eligible. 68Ga-DOTATOC-PET/MRI of up to 5 liver lesions per patients was subsequently analyzed. Extracted features comprise conventional PET parameters, such as maximum and mean standardized uptake value (SUVmax and SUVmean) and ADC values. Furthermore, textural features (TFs) from both modalities were extracted. In patients with multiple 68Ga-DOTATOC-PET/MRI a pair of 2 scans each was analyzed separately and the parameter changes between both scans calculated. The same image analysis was performed in patients with 68Ga-DOTATOC-PET/MRI before PRRT. Differences in PET and ADC maps parameters between PRRT-responders and non-responders were compared using Mann-Whitney test to test differences among groups for statistical significance.
Results:
29 pairs of 68Ga-DOTATOC-PET/MRI scans of 18 patients were eligible for the assessment of treatment-related changes. In 12 cases patients were treated with somatostatin analogues between scans, in 9 cases with PRRT and in 2 cases each patients received local treatment, chemotherapy and sunitinib. Treatment responders showed a statistically significant decrease in lesion volume and a borderline significant decrease in entropy on ADC maps when compared to non-responders. Patients treated with standalone SSA showed a borderline significant decrease in mean and maximum ADC, compared to patients treated with PRRT. No parameters were able to predict treatment response to PRRT on pre-therapeutic 68Ga-DOTATOC-PET/MRI.
Conclusions:
Patients responding to current treatment showed a statistically significant decrease in lesion volume on ADC maps and a borderline significant decrease in entropy. No statistically significant changes in PET parameters were observed. No PET or ADC maps parameters predicted treatment response to PRRT. However, the sample size of this preliminary study is small and further research needed.
Insights
Treatment response in neuroendocrine tumors (NETs) correlates with decreased lesion volume on apparent diffusion coefficient (ADC) maps, but not PET parameters. Pre-treatment imaging did not predict response to peptide receptor radionuclide therapy (PRRT).
Area of Science:
- Radiology
- Nuclear Medicine
- Oncology
Background:
- Neuroendocrine tumors (NETs) often overexpress somatostatin receptors (SSTRs), enabling imaging with 68Ga-DOTATOC positron-emission tomography (PET) and treatment with peptide receptor radionuclide therapy (PRRT).
- SSTR expression can change with treatment, impacting imaging and therapy effectiveness.
- This study investigated changes in PET and apparent diffusion coefficient (ADC) parameters during treatment and their predictive value for PRRT response.
Purpose of the Study:
- To assess changes in 68Ga-DOTATOC-PET/MRI and ADC parameters in NET patients undergoing various treatments.
- To determine if pre-therapeutic 68Ga-DOTATOC-PET/MRI can predict treatment response to PRRT.
Main Methods:
- Retrospective analysis of 68Ga-DOTATOC-PET/MRI scans (including ADC maps) from NET patients with liver metastases.
- Extracted conventional PET parameters (SUVmax, SUVmean) and ADC values, along with textural features.
- Analyzed changes between serial scans and compared parameters between PRRT responders and non-responders.
Main Results:
- Treatment responders showed a significant decrease in lesion volume and a borderline significant decrease in ADC map entropy compared to non-responders.
- Patients treated with somatostatin analogues (SSAs) had a borderline significant decrease in mean and maximum ADC compared to PRRT-treated patients.
- No pre-therapeutic PET or ADC parameters reliably predicted PRRT treatment response.
Conclusions:
- Decreased lesion volume on ADC maps and reduced ADC map entropy are associated with treatment response in NETs.
- PET parameters did not show significant changes related to treatment response.
- Current imaging parameters, including pre-treatment 68Ga-DOTATOC-PET/MRI, cannot predict PRRT response, necessitating further research due to small sample size.
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