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Different technical possibilities of post-therapeutic tandem 90Y/ /177Lu-DOTATATE imaging
Jolanta Kunikowska1, Adam Bajera, Magdalena Sawicka
1Nuclear Medicine Department, Medical University of Warsaw, Poland. jolanta.kunikowska@wum.edu.pl.
Background:
Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms derived from endocrine stem cells.These tumors are characterized by overexpression of somatostatin receptors (SSTR), which is utilized for imaging using SSTR analogs. Peptide receptor radionuclide therapy (PRRT) somatostatin analogs labeled with 90Y and 177Lu in neuroendocrine tumors (NETs) results in symptomatic improvement, prolonged survival,and enhanced quality of life. The post-therapeutic imaging leadsto possibility of biodistribution of therapy. The aim of our study was to describe different possibilities of post-therapeutic imaging in patients underwent tandem therapy 90Y/177Lu-DOTATATE with preliminary results of 90Y PET imaging.
Material And Methods:
Thirty patients (11 men, 19 women; the mean age 55 ± 10.9 y) with histological confirmation of metastatic neuroendocrine tumors (G1 and G2) were treated with tandem therapy 90Y/177Lu-DOTATATE. WHBA scan and SPECT acquisition of the abdomen were performed 24 hours post therapy injection, on the dual-head Varicam camera (ELSCINT) using 177Lu photopeak and 90Y bremsstrahlung. PET imaging of 90Y component was done on Siemens Biograph Truepoint PET/CT (window 511 keV ± 15%)4 hours after 90Y/177Lu-DOTATATE. Additionally phantom studies were performer to analyze the spatial resolution of different protocols.
Results:
Out of all the patients, median OS was 49.8 months and median EFS time 24.3 months. Spatial resolution achieved for 90Y, 177 Lu and PET imaging of 90Y component measured using the phantom of the torso filled up with water was 20 mm, 8 mm and 4-5 mm FWHM, respectively. Spatial resolution in human body in our study was about 30 mm for 90Y, 15 mm for 177Lu and 25-30 mm for PET imaging of 90Y component.
Conclusions:
The theoretically best spatial resolution offers PET scanner, however it is important to keep in mind that 90Y-imaging PET is not used for diagnosis purposes (small activities)but rather to present new possibility of post-therapeutic imaging (substantially higher activities). For post-therapeutic imaging after intravenous radiopharmaceutical administration the best spatial resolution offers standard scintigraphic camera for 90Y/177Lu DOTATATE imaging, with using 177Lu photopeaks. The worst spatial resolution offers standard scintigraphic camera for 90Y/177Lu DOTATATE imaging, with using 90Y bremsstrahlung gammas.
Insights
Post-therapeutic imaging using 90Y/177Lu-DOTATATE in neuroendocrine tumors (NETs) shows potential for biodistribution assessment. Standard scintigraphy with 177Lu photopeaks offers the best spatial resolution for this peptide receptor radionuclide therapy.
Area of Science:
- Nuclear Medicine
- Radiopharmaceutical Therapy
- Oncology
Background:
- Neuroendocrine tumors (NETs) are characterized by somatostatin receptor (SSTR) overexpression.
- SSTR analogs are used for NET imaging and Peptide Receptor Radionuclide Therapy (PRRT).
- Tandem therapy with 90Y/177Lu-DOTATATE improves survival and quality of life in NET patients.
Purpose of the Study:
- To evaluate post-therapeutic imaging possibilities after 90Y/177Lu-DOTATATE tandem therapy in NET patients.
- To assess the preliminary results of 90Y PET imaging for biodistribution analysis.
- To compare the spatial resolution of different imaging techniques for 90Y and 177Lu.
Main Methods:
- Thirty metastatic NET patients (G1/G2) received 90Y/177Lu-DOTATATE tandem therapy.
- Whole-body planar imaging (WHBA) and SPECT were performed 24 hours post-injection.
- 90Y PET imaging was conducted 4 hours post-injection; phantom studies analyzed spatial resolution.
Main Results:
- Median overall survival (OS) was 49.8 months; median event-free survival (EFS) was 24.3 months.
- Phantom spatial resolution: 20 mm (90Y), 8 mm (177Lu), 4-5 mm (90Y PET).
- In vivo spatial resolution: ~30 mm (90Y), 15 mm (177Lu), 25-30 mm (90Y PET).
Conclusions:
- PET offers theoretically best spatial resolution but is used for high activity post-therapy, not diagnosis.
- Standard scintigraphy using 177Lu photopeaks provides the best spatial resolution for 90Y/177Lu-DOTATATE imaging.
- 90Y bremsstrahlung imaging yields the worst spatial resolution with standard scintigraphy.
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