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99mTc-depreotide tumour uptake in patients with non-Hodgkin's lymphoma
David L Bushnell1, Yusuf Menda, Mark T Madsen
1Iowa City Veterans Administration Hospital, Diagnostic Imaging and Radioisotope Therapy Service, Iowa City, IA 52246, USA. david-bushnell@uiowa.edu
Background:
99mTc-depreotide (NeoTect) is a synthetic somatostatin analogue, which binds to somatostatin receptor (SSTR) subtypes 2, 3 and 5. Imaging patients with non-Hodgkin's lymphoma (NHL) using the somatostatin analogue In-pentetreotide (Octreoscan) has demonstrated the feasibility of identifying lymphoma sites with this class of peptide radiopharmaceutical. SSTR peptides can be labelled with beta emitters and, if sufficient tumour uptake relative to normal organs can be demonstrated, therapeutic applications can be considered.
Methods:
In this prospective Institutional Review Board (IRB)-approved study, patients with NHL and a recent computed tomography (CT) examination were eligible. Whole-body and selected single-photon emission computed tomography (SPECT) imaging was performed 1 h after intravenous injection of 99mTc-depreotide. Images were compared with CT scan findings. The radioactivity concentration of 99mTc-depreotide in abdominal/pelvic tumour sites, together with normal organs, was determined and expressed as the percentage of injected activity per gram of tissue (%IA x g).
Results:
Paired CT and 99mTc-depreotide images for three patients with indolent and six with aggressive NHL revealed abnormal 99mTc-depreotide uptake corresponding to the tumour seen on CT in seven of these patients. In three of the patients, all known tumour sites were detected on 99mTc-depreotide images. The mean %IA x g for nine abdominal/pelvic tumour foci from four patients was found to be 0.004% (range, 0.001-0.007%). The mean tumour to bone marrow activity concentration ratio in these four patients was found to be 0.94 (range, 0.33-1.40), whereas the tumour to kidney ratio was 0.53 (range, 0.16-0.80).
Conclusions:
Levels of 99mTc-depreotide in tumour suggest at least the possibility of potential therapy with beta emitter-labelled SSTR peptides; however, depreotide itself appears not to be a suitable candidate as a targeting agent due to the relatively high bone marrow concentration.
Insights
99mTc-depreotide imaging detected non-Hodgkin
Area of Science:
- Nuclear Medicine
- Oncology
- Radiopharmaceutical Development
Background:
- 99mTc-depreotide is a somatostatin receptor (SSTR) targeting peptide with potential for imaging and therapy.
- Previous studies demonstrated feasibility of SSTR peptide imaging for non-Hodgkin's lymphoma (NHL).
- Therapeutic applications of SSTR peptides are considered if sufficient tumor uptake is achieved.
Purpose of the Study:
- To evaluate the diagnostic performance of 99mTc-depreotide for detecting non-Hodgkin's lymphoma (NHL).
- To assess the uptake of 99mTc-depreotide in NHL tumor sites and normal organs.
- To determine the suitability of 99mTc-depreotide as a targeting agent for potential therapeutic applications.
Main Methods:
- Prospective study of patients with NHL undergoing computed tomography (CT) and 99mTc-depreotide imaging.
- Whole-body and single-photon emission computed tomography (SPECT) imaging performed 1 hour post-injection.
- Quantification of radioactivity concentration in tumor sites and normal organs (%IA x g).
Main Results:
- 99mTc-depreotide imaging detected lymphoma sites in 7 out of 9 patients with NHL, correlating with CT findings.
- All known tumor sites were identified in 3 patients.
- Mean tumor uptake was 0.004% IA/g, with tumor-to-bone marrow and tumor-to-kidney ratios of 0.94 and 0.53, respectively.
Conclusions:
- 99mTc-depreotide shows potential for NHL detection, suggesting feasibility for targeted therapy with beta-emitter labeled SSTR peptides.
- Depreotide's relatively high bone marrow uptake limits its suitability as a therapeutic targeting agent.
- Further development of SSTR peptide radiopharmaceuticals for NHL therapy is warranted.
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