Quantitative analysis of standardized uptake values (SUV) of metastatic bone lesions in scintigraphy with [99mTc]Tc-EDDA/HYNIC-Tyr3-octreotide in patients with neuroendocrine tumours.

BACKGROUND: Neuroendocrine tumours (NETs) are a group of cancers that can produce hormones and other metabolically active compounds. The majority of NETs have specific tissue characteristics, such as the expression of somatostatin receptors (SSTR). Metabolic testing with [99mTc]Tc-EDDA/HYNIC-Tyr3-octreotide ([99mTc]Tc-EDDA/HYNIC-TOC) can be used in patients with NETs to visualize the presence of receptors in different locations of pathological lesions, including the skeletal system. The study aimed to calculate the body weight maximum standardized uptake value (SUVbwmax) of pathological bone lesions and healthy bone tissues, estimate the size of lesions, and identify a relationship between the SUVbwmax of the bone tissues, age and body mass of the study participants. MATERIAL AND METHODS: The somatostatin receptor scintigraphies (SRS) with [99mTc]Tc-EDDA/HYNIC-TOC were carried out at the Department of Nuclear Medicine, University Clinical Hospital No. 1, Pomeranian Medical University (PMU) in Szczecin from 2019 to 2022. Whole body and single photon emission computed tomography/computed tomography (SPECT/CT) scans were performed four hours after the injection of 700-800 MBq of [99mTc]Tc-EDDA/HYNIC-TOC in 344 patients with neuroendocrine tumours of various primary lesion locations. In 19 patients, who showed foci of increased radiopharmaceutical accumulation in bone location, the SUVbwmax was measured. The SUVbwmax of pathological bone lesions and healthy tissues were determined on SPECT/CT cross-sectional images using Xeleris 4 software. RESULTS: The total number of foci with increased SSTR expression in bone regions seen on scintigraphic images was 89. Among them, 32 bone lesions were visible on the corresponding CT scans. The mean SUVbwmax of these lesions was 31.39 [standard deviation (SD) 34.31]. For the other 57 lesions that were not visible on corresponding CT scans, the mean SUVbwmax was 19.12 (SD 24.24). The smallest bone lesion detected on the scintigram and visible on the corresponding CT location was 5 mm × 5 mm, measured in cross-section, and was located in the Th8 vertebral body; the largest, measuring 20 mm × 22 mm, was detected in the L3 vertebral body. The SUVbwmax of these lesions was 24.70 and 142.40, respectively. CONCLUSIONS: Bone lesions seen on SPECT/CT in [99mTc]Tc-EDDA/HYNIC-TOC scintigraphy can be quantitatively analysed using the SUV index. Even a very small pathological bone lesion can be detected on [99mTc]Tc-EDDA/HYNIC-TOC scintigraphy. It was shown that in cases where bone lesions were visible on CT scans, the SUVbwmax of bone tumour lesions was higher than when lesions were not visible on CT. Body mass does not affect the SUVbwmax of bone lesions. SUVbwmax of healthy bone tissue decreased with age.

Optimized Production of 188Re-HYNIC-Bombesin: New Therapeutic Agent for GRPR Targeting.

Purpose: One of the most interesting methods to deliver therapeutic doses of ionizing radiation to tumor sites is radiolabeled compounds. Bombesin peptide binds to gastrin-releasing peptide receptors (GRPRs) with great affinity. Through its appropriate physical characteristics and accessibility as the 188W/188Re generator, 188Re can be effectively used to develop a therapeutic radio complex. In this study, 188Re-HYNIC-BBN was prepared under optimal conditions. Methods: Optimization of the effective parameters on 188Re-HYNIC-BBN radio-labeling yield like ligand concentration, pH, reaction time, and temperature were performed. The final product's radiochemical purity was measured by RTLC and HPLC. The stability of the radio-complex was checked in PBS buffer (4 °C) and human blood serum (37 °C). The partition coefficient of the final radio-complex was studied using standard procedure. Finally, the biodistribution of 188Re-HYNIC-BBN and free 188Re in different organs of the rats were compared in various intervals. Results: The final product was prepared with a specific activity of 7.11 TBq/mmol and radiochemical purity > 95% at the optimized conditions (pH = 4-5, reaction time = 45 min, temp = 95℃). This radio-complex was found to be stable in PBS and blood serum over 24 h. LogPo/w was - 1.78, showing the high hydrophilic nature of the radio-complex. The biodistribution of 188Re-HYNIC-BBN demonstrated the fast clearance of the radio-peptide from the blood circulation. The most portion of the radioactivity was excreted from the body via the urinary tract and the remaining activity was accumulated in GRPR-expressing organs. Conclusion: The special characteristics of the complex introduce 188Re-HYNIC-BBN as a new therapeutic agent for targeting GRPRs, however, more biological data is still needed.

Calcitonin-producing Duodenal Neuroendocrine Tumor: A Case Report and Literature Review.

INTRODUCTION: Neuroendocrine tumors [NETs] exhibit a wide range of clinical presentations, including the production of various hormones. Calcitonin, a sensitive marker for medullary thyroid cancer [MTC], is nonspecific and may be elevated in extra-thyroidal NETs. CASE REPORT: We present the case of a 64-year-old female patient who underwent total thyroidectomy due to a nodule in the isthmus, with a fine-needle aspiration biopsy indicating follicular neoplasia. Pathological examination revealed macro- and micro-nodular thyroid hyperplasia, along with a parathyroid adenoma. During postoperative follow-up, a progressive elevation of calcitonin was observed, reaching 64.2 pg/ml, while carcinoembryonic antigen levels remained normal. Since no MTC foci were found upon reviewing the thyroidectomy specimen, an investigation into the origin of the elevated calcitonin was initiated. Serum chromogranin A and specific neuronal enolase levels were within normal ranges. Tc-99m HYNIC-TOC scintigraphy yielded negative results. Additionally, an upper gastrointestinal endoscopy revealed a submucosal lesion in the second portion of the duodenum, with a biopsy confirming a grade 1 NET. The patient underwent Whipple surgery and hepatic metastasectomy. Postoperatively, a decrease in baseline serum calcitonin levels was observed. Seven years after surgery, she continues specialized monitoring with no biochemical or imaging evidence of disease. CONCLUSION: Serum calcitonin contributes to the diagnosis and monitoring of anterior intestine NETs.

[99mTc]Tc-labeled HYNIC conjugated chlorambucil as a tumor targeting Agent: Synthesis, characterization and ex-vivo evaluation.

Chlorambucil is an alkylating drug that finds application towards chemotherapy of different types of cancers. In order to explore the possibility of utilization of this drug as an imaging agent for early diagnosis of solid tumors, attempt was made to synthesize a 99mTc complex of chlorambucil and evaluate its potential in tumor bearing small animal model. HYNIC-chlorambucil was synthesized by conjugation of HYNIC with chlorambucil via an ethylenediamine linker. All the intermediates and final product were purified and characterized by standard spectroscopic techniques viz. FT-IR, 1H/13C-NMR as well as by mass spectrometry. HYNIC-chlorambucil conjugate was radiolabeled with [99mTc]Tc and found to be formed with > 95 % radiochemical purity via RP-HPLC studies. The partition coefficient (Log10Po/w) of the synthesized complex was found to be -0.78 ± 0.25 which indicated the moderate hydrophilic nature for the complex. Biological behaviour of [99mTc]Tc-HYNIC-chlorambucil, studied in fibrosarcoma bearing Swiss mice, revealed a tumor uptake of about 4.16 ± 1.52 %IA/g at 30 min post-administration, which declined to 1.91 ± 0.13 % IA/g and 1.42 ± 0.14 %IA/g at 1 h and 2 h post-administration, respectively. A comparison of different [99mTc]Tc-chlorambucil derivatives (reported in the contemporary literature) formulated using different methodologies revealed that tumor uptake and pharmacokinetics exhibited by these agents strongly depend on the lipophilicity/hydrophilicity of such agents, which in turn is dependent on the bifunctional chelators used for formulating the radiolabeled chlorambucils.

Comparative Preclinical Evaluation of HYNIC-Modified Designed Ankyrin Repeat Proteins G3 for the 99mTc-Based Imaging of HER2-Expressing Malignant Tumors.

HER2 status determination is a necessary step for the proper choice of therapy and selection of patients for the targeted treatment of cancer. Targeted radiotracers such as radiolabeled DARPins provide a noninvasive and effective way for the molecular imaging of HER2 expression. This study aimed to evaluate tumor-targeting properties of three 99mTc-labeled DARPin G3 variants containing Gly-Gly-Gly-Cys (G3C), (Gly-Gly-Gly-Ser)3-Cys ((G3S)3C), or Glu-Glu-Glu-Cys (E3C) amino acid linkers at the C-terminus and conjugated to the HYNIC chelating agent, as well as to compare them with the clinically evaluated DARPin G3 labeled with 99mTc(CO)3 using the (HE)3-tag at the N-terminus. The labeling of DARPin G3-HYNIC variants provided radiochemical yields in the range of 50-80%. Labeled variants bound specifically to human HER2-expressing cancer cell lines with affinities in the range of 0.5-3 nM. There was no substantial influence of the linker and HYNIC chelator on the binding of 99mTc-labeled DARPin G3 variants to HER2 in vitro; however, [99mTc]Tc-G3-(G3S)3C-HYNIC had the highest affinity. Comparative biodistribution of [99mTc]Tc-G3-G3C-HYNIC, [99mTc]Tc-G3-(G3S)3C-HYNIC, [99mTc]Tc-G3-E3C-HYNIC, and [99mTc]Tc-(HE)3-G3 in healthy CD1 mice showed that there was a strong influence of the linkers on uptake in normal tissues. [99mTc]Tc-G3-E3C-HYNIC had an increased retention of activity in the liver and the majority of other organs compared to the other conjugates. The tumor uptake of [99mTc]Tc-G3-(G3S)3C-HYNIC and [99mTc]Tc-(HE)3-G3 in Nu/j mice bearing SKOV-3 xenografts was similar. The specificity of tumor targeting in vivo was demonstrated for both tracers. [99mTc]Tc-G3-(G3S)3C-HYNIC provided comparable, although slightly lower tumor-to-lung, tumor-to spleen and tumor-to-liver ratios than [99mTc]Tc-(HE)3-G3. Radiolabeling of DARPin G3-HYNIC conjugates with 99mTc provided the advantage of a single-step radiolabeling procedure; however, the studied HYNIC conjugates did not improve imaging contrast compared to the 99mTc-tricarbonyl-labeled DARPin G3. At this stage, [99mTc]Tc-(HE)3-G3 remains the most promising candidate for the clinical imaging of HER2-overexpressing cancers.

[99mTc]Tc-HYNIC-ALUG SPECT/CT in the initial staging of 227 consecutive patients with newly diagnosed prostate cancer: a 5-year monocentric retrospective study.

Purpose: The purpose of this study was to assess the effectiveness of [99mTc]Tc-HYNIC-ALUG SPECT/CT in the initial staging of patients with newly diagnosed PCa. Methods: A retrospective analysis was conducted on 227 consecutive patients who underwent [99mTc]Tc-HYNIC-ALUG SPECT/CT imaging for the primary staging of newly diagnosed PCa. The presence and location of PSMA-positive lesions were determined, and the maximum standardized uptake values (SUVmax) of the primary prostate tumor were also measured. The metastatic findings and SUVmax were stratified according to International Society of Urological Pathology (ISUP) grade, prostate-specific antigen (PSA) levels, and D'Amico classification. Furthermore, the [99mTc]Tc-HYNIC-ALUG SPECT/CT findings were compared to the histopathological findings in patients who had undergone radical prostatectomy with pelvic lymph node dissection (PLND). Results: Of the 227 patients, 92.1% (209/227) had positive [99mTc]Tc-HYNIC-ALUG SPECT/CT findings. Advanced disease was detected in 38.8% (88/227) of the patients and was positively correlated with increasing ISUP grade and PSA levels. Lymph node metastases (both pelvic and extrapelvic), bone metastases, and visceral metastases were detected in 30.0% (68/227), 25.6% (58/227), and 3.1% (7/227) of the patients, respectively. For the 129 patients who underwent radical prostatectomy with PLND, the sensitivity of [99mTc]Tc-HYNIC-ALUG SPECT/CT in the evaluation of PCa was 90.7% (117/129). The sensitivity, specificity, accuracy, and positive and negative predictive values for detecting pelvic lymph node metastases on [99mTc]Tc-HYNIC-ALUG SPECT/CT were 23.5% (12/51), 93.6% (73/78), 65.9% (85/129), 70.6% (12/17), and 65.2% (73/112), respectively. Among the 209 patients with PSMA-avid primary prostate disease, the SUVmax of the primary prostate tumor was significantly associated with ISUP grade (p<0.0001), PSA levels (p<0.0001), D'Amico classification (p<0.0001), and advanced disease (p<0.0001). Receiver operating characteristic (ROC) analysis revealed that a PSA level >19.8 ng/ml and SUVmax of the primary prostate tumor >7.4 had a sensitivity of 71.6% and 71.6% and specificity of 76.9% and 82.6%, respectively, for detecting metastatic disease. Conclusions: [99mTc]Tc-HYNIC-ALUG SPECT/CT emerges as a valuable imaging tool for the initial staging of newly diagnosed PCa. The presence of advanced disease and the SUVmax of the primary prostate tumor were positively correlated with ISUP grade and PSA levels.

PPY-cell hyperplasia accompanying NENs: Immunohistochemical and nuclear medicine analysis.

Pancreatic polypeptide cell hyperplasia (PPY-H) is a multiplication of the neuroendocrine cells producing pancreatic polypeptide (PPY). The development and role of PPY-H and its corresponding clinical and imaging findings still need to be fully elucidated. We present 12 cases of PPY-H accompanying pancreatic neuroendocrine neoplasias (NEN). PPY-H was analyzed with the help of immunohistochemistry and confocal microscopy; preoperative clinical data and imaging studies were evaluated retrospectively. We observed PPY-H emerging from pancreatic ducts, and in some cases, we observed simultaneous NKX6.1 positivity in ducts and PPY-H. Additional clinical-pathological correlations suggests that gastrointestinal symptoms (e.g., epigastric pain and cholestasis) could be more related to PPY-H than to NEN hormonal production. In particular cases, SSTR2 expression was strong in PPY-H and correlated with distinguishable accumulation of activity next to NEN on 99 mTc EDDA/Hynic-TOC SPECT/CT. In another case, 18F-FDG-PET/CT showed increased metabolic activity in the area of PPY-H surrounding NEN. Our data suggest that PPY-H originates in the lining of pancreatic ducts. Confirmation of SSTR2 in PPY-H, using immunohistochemistry, suggests the utility of 99 mTc EDDA/Hynic-TOC or 68Ga-DOTA radiotracers in clinical diagnostics; however, studies with larger cohort are needed.

Radiolabeling of Platelets with 99mTc-HYNIC-Duramycin for In Vivo Imaging Studies.

Following the in vivo biodistribution of platelets can contribute to a better understanding of their physiological and pathological roles, and nuclear imaging methods, such as single photon emission tomography (SPECT), provide an excellent method for that. SPECT imaging needs stable labeling of the platelets with a radioisotope. In this study, we report a new method to label platelets with 99mTc, the most frequently used isotope for SPECT in clinical applications. The proposed radiolabeling procedure uses a membrane-binding peptide, duramycin. Our results show that duramycin does not cause significant platelet activation, and radiolabeling can be carried out with a procedure utilizing a simple labeling step followed by a size-exclusion chromatography-based purification step. The in vivo application of the radiolabeled human platelets in mice yielded quantitative biodistribution images of the spleen and liver and no accumulation in the lungs. The performed small-animal SPECT/CT in vivo imaging investigations revealed good in vivo stability of the labeling, which paves the way for further applications of 99mTc-labeled-Duramycin in platelet imaging.

Design of a New 99mTc-radiolabeled Cyclo-peptide as Promising Molecular Imaging Agent of CXCR4 Receptor: Molecular Docking, Synthesis, Radiolabeling, and Biological Evaluation.

INTRODUCTION: C-X-C Chemokine receptor type 4 (CXCR4) is often overexpressed or overactivated in different types and stages of cancer disease. Therefore, it is considered a promising target for imaging and early detection of primary tumors and metastasis. In the present research, a new cyclo-peptide radiolabelled with 99mTc, 99mTc-Cyclo [D-Phe-D-Tyr-Lys (HYNIC)- D-Arg-2-Nal-Gly-Lys(iPr)], was designed based on the parental LY251029 peptide, as a potential in vivo imaging agent of CXCR4-expressing tumors. METHODS: The radioligand was successfully prepared using the method of Fmoc solid-phase peptide synthesis and was evaluated in biological assessment. Molecular docking findings revealed high affinity (binding energy of -9.7 kcal/mol) and effective interaction of Cyclo [D-Phe- D-Tyr-Lys (HYNIC)-D-Arg-2-Nal-Gly-Lys(iPr)] in the binding pocket of CXCR4 receptor (PDB code: 3OE0) as well. RESULT: The synthesized peptide and its purity were assessed by both reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectroscopy. High stability (95%, n = 3) in human serum and favorable affinity (Kd = 28.70 ± 13.56 nM and Bmax = 1.896 ± 0.123 fmol/mg protein) in the B16-F10 cell line resulted. Biodistribution evaluation findings and planar image interpretation of mice both showed high affinity and selectivity of the radiotracer to the CXCR4 receptors. CONCLUSION: Therefore, the findings indicate this designed radioligand could be used as a potential SPECT imaging agent in highly proliferated CXCR4 receptor tumors.

Diagnostic accuracy of 99mTc-HYNIC-TOC SPECT/CT for detecting osteomalacia-associated tumors.

Objectives: Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic disorder characterized by hypophosphatemia resulting from tumor-secreted fibroblast growth factor-23 (FGF23). Surgical resection of the culprit TIO is the first choice of treatment. However, TIO is difficult to detect with conventional diagnostic tools due to its small size and variable location in the body. Somatostatin receptor scintigraphy (SSR) has recently emerged as a functional molecular imaging choice for TIO detection and localization. This research was undertaken to evaluate the efficacy of 99mTc-labeled hydrazinonicotinyl-Tyr3-octreotide (99mTc-HYNIC-TOC) SPECT/CT in detecting TIO. Methods: 99mTc-HYNIC-TOC SPECT/CT and the available clinical data of 25 patients with suspected TIO were analyzed retrospectively. The 99mTc-HYNIC-TOC SPECT/CT findings were compared with the post-surgical pathology diagnosis and clinical follow-up results. Results: Using 99mTc-HYNIC-TOC SPECT/CT, suspicious tumors were found in 18 of the 25 patients, and 15 of them underwent surgical resection. The post-operative pathology confirmed a TIO in those 13 patients whose symptoms and biochemical anomalies gradually resolved after the surgery. The remaining five patients were finally considered false positives. Moreover, the 99mTc-HYNIC-TOC SPECT/CT results were negative in seven patients, with six patients being true negative (4 patients were diagnosed with acquired Fanconi syndrome and 2 patients responded well to conservative therapy) and one being false negative. Therefore, the sensitivity and specificity values of 99mTc-HYNIC-TOC SPECT/CT in the evaluation of TIO were 92.9% (13/14) and 54.5% (6/11), respectively. The overall accuracy of 99mTc-HYNIC-TOC SPECT/CT for detecting TIO was 76.0% (19/25). Conclusions: The 99mTc-HYNIC-TOC SPECT/CT is an accurate imaging modality for locating culprit tumors in TIO.

Synthesis and Evaluation of 99mTc-Labeled PSMA-Targeted Tracers Based on the Lys-Urea-Aad Pharmacophore for Detecting Prostate Cancer with Single Photon Emission Computed Tomography.

Prostate-specific membrane antigen (PSMA) is a well-validated prostate cancer marker but reported PSMA-targeted tracers derived from the Lys-urea-Glu pharmacophore including the clinically validated [99mTc]Tc-EDDA/HYNIC-iPSMA have high off-target uptake in kidneys, spleen, and salivary glands. In this study, we synthesized and evaluated three novel 99mTc-labeled PSMA-targeted tracers and investigated if the tracers derived from the Lys-urea-Aad pharmacophore could have minimized uptake in off-target organs/tissues. In vitro competition binding assays showed that compared with HYNIC-iPSMA, the three novel ligands had slightly weaker PSMA binding affinity (average Ki = 3.11 vs. 8.96-11.6 nM). Imaging and ex vivo biodistribution studies in LNCaP tumor-bearing mice showed that [99mTc]Tc-EDDA/HYNIC-iPSMA and the three novel tracers successfully visualized LNCaP tumor xenografts in SPECT images and were excreted mainly via the renal pathway. The average tumor uptake at 1 h post-injection varied from 5.40 to 18.8%ID/g, and the tracers derived from the Lys-urea-Aad pharmacophore had much lower uptake in the spleen and salivary glands. Compared with the clinical tracer [99mTc]Tc-EDDA/HYNIC-iPSMA, the Lys-urea-Aad-derived [99mTc]Tc-EDDA-KL01127 had lower background uptake and superior tumor-to-background contrast ratios and is therefore promising for clinical translation to detect prostate cancer lesions with SPECT.

The efficacy of 99mTc-HYNIC-PSMA SPECT/CT in detecting primary lesions and metastasis in newly diagnosed prostate cancer.

Purpose: Compared with PET/CT or PET/MRI, SPECT/CT is cheaper and more readily accessible. This study was designed to investigate the efficacy of 99mTc-HYNIC-PSMA SPECT/CT in detecting primary tumors and metastases in patients with newly diagnosed prostate cancer (PCa). Methods: A retrospective analysis of 31 patients with pathologically proven PCa was performed at Shanghai General Hospital from November 2020 to November 2021. Planar whole-body imaging was performed on all patients with a SPECT/CT scan of PSMA-positive regions 3-4 h after intravenous injection of 740 MBq 99mTc-HYNIC-PSMA. Positive PSMA uptake lesions were evaluated, and SUVmean and SUVmax were measured in each lesion. Associations between SPECT/CT parameters and clinicopathologic factors (tPSA and Gleason Score) were analyzed. The diagnostic capability of SPECT/CT parameters, tPSA, and GS in distant metastatic detection was evaluated by logistic regression. Results: The SUVmean and SUVmax of the high-risk stratification subgroups (tPSA>20 ng/ml, GS ≥8, and tPSA >20 ng/ml and GS≥8) were higher than those of the low-moderate risk stratification subgroups, with sensitivities of 92% and 92%, respectively. Neither SPECT/CT parameters (SUVmean, SUVmax) nor clinicopathologic factors (tPSA, GS) had high sensitivity (80%, 90%, 80%, and 90%, respectively, P <0.05) in distant metastatic prediction. For both the guideline tPSA level (20 ng/ml) and the cut-off level (84.3 ng/ml), the difference in the distant metastasis detection rate between the low predicted tPSA group and the high predicted tPSA group was statistically significant (0% vs. 47.62%, P = 0.005; 9.09% vs. 88.89%, P = 0.000, respectively). Twenty patients with pathological 99mTc-PSMA avid only in the prostate beds underwent radical prostatectomy. Seven of them underwent lymph node dissection, a total of 35 lymph nodes were removed, and no lymph nodes were detected with metastasis, which was consistent with 99mTc-HYNIC-PSMA SPECT/CT. Conclusion: 99mTc-HYNIC-PSMA SPECT/CT is effective in the risk stratification and distant metastasis detection of primary PCa patients. It is of great value in guiding treatment strategies.

SPECT Imaging with Tc-99m-Labeled HYNIC-FAPI-04 to Extend the Differential Time Window in Evaluating Tumor Fibrosis.

The so-far used Ga-68- or F-18-labelled tracers are of a relative short time window in differentiating tumor fibrosis. SPECT applicable imaging probe, 99mTc-HYNIC-FAPI-04, was synthesized and evaluated in tumor cells and animal models of FAP-positive glioma and FAP-negative hepatoma, and then compared with 18F-FDG or 68Ga-FAPI-04 PET/CT. The radio-labeling rate of 99mTc-HYNIC-FAPI-04 was greater than 90%, and the radiochemical purity was >99% after purification with sep-pak C18 column. In vitro cell uptake experiments of 99mTc-HYNIC-FAPI-04 showed good FAP binding specificity, and the cellular uptake significantly decreased when blocked by DOTA-FAPI-04, reflecting the similar targeting mechanism of HYNIC-FAPI-04 and DOTA-FAPI-04. SPECT/CT imaging showed that U87MG tumor was distinguishable and of a high uptake of 99mTc-HYNIC-FAPI-04 (2.67 ± 0.35 %ID/mL at 1.5 h post injection (h P.I.), while tumor signal of FAP-negative HUH-7 was as low as 0.34 ± 0.06 %ID/mL. At 5 h P.I., U87MG tumor was still distinguishable (1.81 ± 0.20 %ID/mL). In comparison, although U87MG tumor was of obvious 68Ga-FAPI-04 uptake and clearly visible at 1 h P.I., the tumorous radioactive signals were fuzzy at 1.5 h P.I. 99mTc-HYNIC-FAPI-04 specifically bound to FAP-positive tumors and qualified with the ability of evaluating tumor fibrosis over longer time windows.

[99mTc]Tc-HYNIC-RM2: A potential SPECT probe targeting GRPR expression in prostate cancers.

INTRODUCTION: Elevated density of gastrin releasing peptide receptors (GRPR) in prostate cancer has led to exploration of several radiolabeled peptides for imaging and staging of the disease. The GRPR antagonist peptide RM2 has been successfully conjugated with several chelators and radiolabeled with gallium-68. The goal of this study was to synthesize a 99mTc-labeled probe and investigate its potential for SPECT imaging of prostate cancer. Towards this HYNIC-RM2 peptide conjugate was synthesized, radiolabeled with 99mTc and evaluated in GRPR-positive PC3 tumor xenografts. METHODS: HYNIC-RM2 was manually synthesized by standard Fmoc solid phase strategy and radiolabeled with 99mTc. In vitro cell studies were performed in GRPR-positive human prostate carcinoma (PC3) cells. Metabolic stability studies of [99mTc]Tc-HYNIC-RM2 were performed in normal mice in the presence as well as absence of neutral endopeptidase (NEP) inhibitor, phosphoramidon (PA). Biodistribution and imaging studies of [99mTc]Tc-HYNIC-RM2 were performed in SCID mice bearing PC3-xenograft. RESULTS: [99mTc]Tc-HYNIC-RM2 exhibited high binding affinity in low nanomolar range (Kd = 1.83 ± 0.31 nM). Metabolic stability studies in mice indicated that in the absence of PA, radiolabeled peptide was about 65 % intact in the blood at 15 min p.i., whereas proportion of intact radiolabeled peptide was enhanced to 90 % on co-administration of PA. Biodistribution studies in PC3 tumor bearing mice demonstrated high tumor uptake (8.02 ± 0.9%ID/g and 6.13 ± 0.44%ID/g at 1 h and 3 h p.i.). Co-administration of PA with the radiolabeled peptide resulted in further enhancement of tumor uptake (14.24 ± 0.76 % ID/g and 11.71 ± 0.59%ID/g at 1 h and 3 h p.i.). SPECT/CT images of [99mTc]Tc-HYNIC-RM2 could clearly visualize the tumor. Significant (p < 0.001) reduction in the tumor uptake with a co-injected blocking dose of unlabeled peptide ascertained the GRPR specificity of [99mTc]Tc-HYNIC-RM2. CONCLUSION: Encouraging results obtained in biodistribution and imaging studies indicate the potential of [99mTc]Tc-HYNIC-RM2 for further exploration as GRPR targeting agent.

Comparative Evaluation of 99mTc-Octreotide for Diagnostic Accuracy Assessment and Localization of 177Lu-DOTA-TATE in Neuroendocrine Tumors.

INTRODUCTION: Neuroendocrine tumors, due to uncommon and multi-centric origin, pose a clinical challenge for their diagnosis and treatment. Developing countries where Ga-68 DOTA-TOC/NOC PET imaging is very limited and costly, 99mTc based SSR imaging can be used as the key tool for its diagnosis and assessment of therapy response. Hence we used two different 99mTc-radiopharmaceuticals for NET imaging designated as RP-1 and RP-2 for clinical assessment and peptide receptor therapy response of 177Lu-DOTA-TATE by manually synthesized acetate buffer. 99mTc- labeled RP-1 and RP-2 sensitivity, specificity; positive and negative predictive values were calculated and compared by SPECT/CT images for utilization in peptide receptor radionuclide therapy (PRRT). METHOD: Sodium-pertechnetate was used for labeling both radiopharmaceuticals, while 177Lu nca (0.04 N HCl) DOTA-TATE was synthesized by 0.1M ammonium acetate/ascorbic acid. 75 patients of known primary NET imaging with RP-1 and RP-2 were evaluated for SRR avidity and 3 were selected for PRRT. All images were correlated with 68Ga-DOTA-TOC scan, histopathology, CT and/or MRI reports. RESULTS: Out of 75 patients, the somatostatin receptor imaging of 39 patients of neuro-endocrine was performed with RP-1, found 23 as true positive, 7 as true negative with sensitivity, specificity, PPV and NPV of 71.87%, 100%, 100% and 43.75%, whereas 36 images with RP-2 calculated 22 T/P, 6 as T/N, 8 as F/N, with 75.8%, 100%, 100% and 50% respectively. Their 177Lu-DOTA-TATE SPECT/CT revealed specific localization of therapeutic radionuclide. CONCLUSION: 99mTc-imaging of RP-2, as compared to RP-1, had better efficiency and sensitivity and could effectively be used as an alternative to Ga-68 DOTA/TOC PET imaging and Lu-177 DOTA-TATE PRRT therapy response evaluation.

Standardized Uptake Values on SPECT/CT: A Promising Alternative Tool for Treatment Evaluation and Prognosis of Metastatic Neuroendocrine Tumours.

(1) Background: The aim of our study was to assess the feasibility of 99mTcEDDA/HYNIC-TOC SPECT/CT quantitative analysis in evaluating treatment response and disease progression in patients with NETs. (2) Methods: This prospective monocentric study evaluated 35 SPECT/CT examinations performed on 14 patients with neuroendocrine tumours who underwent a baseline and at least one follow-up 99mTcEDDA/HYNIC-TOC scan as part of their clinical management. The examination protocol included a whole-body scan acquired 2 h after the radiotracer's administration, with the SPECT/CT performed 4 h post-injection. Images were analyzed by two experienced physicians and patients were classified into response categories based on their changes in SUV values. (3) Results: We evaluated 14 baseline studies and 21 follow-up scans, accounting for 123 lesions. A statistically positive correlation has been found between the SUVmax and SUVpeak values in tumoral lesions (p < 0.05). No correlation has been found between the SUV values and the ki67 proliferation index. Finally, 64.29% patients were classified as SD at the end of the study, with only 14.29% of patients exhibiting PD and 21.43% patients with PR. (4) Conclusions: The quantitative analysis of 99mTcEDDA/HYNIC-TOC SPECT/CT data in patients with neuroendocrine tumours could represent an alternative to 68Ga-DOTA-peptides PET/CT for the monitoring and prognosis of NETs.

Synthesis and Bioevaluation of Novel Technetium-99m-Labeled Complexes with Norfloxacin HYNIC Derivatives for Bacterial Infection Imaging.

To seek a novel 99mTc-labeled quinolone derivative for bacterial infection SPECT imaging that aims to lower nontarget organ uptake, a novel norfloxacin 6-hydrazinoicotinamide (HYNIC) derivative (HYNICNF) was designed and synthesized. It was radiolabeled with different coligands, such as tricine, trisodium triphenylphosphine-3,3',3″-trisulfonate (TPPTS), sodium triphenylphosphine-3-monosulfonate (TPPMS), and ethylenediamine-N,N'-diacetic acid (EDDA), to obtain three 99mTc-labeled norfloxacin HYNIC complexes, namely, [99mTc]Tc-tricine-TPPTS-HYNICNF, [99mTc]Tc-tricine-TPPMS-HYNICNF, and [99mTc]Tc-EDDA-HYNICNF. These complexes were purified (RCP > 95%) and evaluated in vitro and in vivo for targeting bacteria. All three complexes are hydrophilic, maintain good stability, and specifically bind Staphylococcus aureus in vitro. The biodistribution in mice with bacterial infection demonstrated that [99mTc]Tc-EDDA-HYNICNF showed a higher abscess uptake and lower nontarget organ uptake and was able to distinguish bacterial infection and sterile inflammation. Single photon emission computed tomography (SPECT) image study in bacterial infection mice showed there was a visible accumulation in the infection site, suggesting that [99mTc]Tc-EDDA-HYNICNF is a potential radiotracer for bacterial infection imaging.

Development and Characterization of 99mTc-scFvD2B as a Potential Radiopharmaceutical for SPECT Imaging of Prostate Cancer.

Previously, we demonstrated that the 177Lu-labeled single-chain variable fragment of an anti-prostate-specific membrane antigen (PSMA) IgG D2B antibody (scFvD2B) showed higher prostate cancer (PCa) cell uptake and tumor radiation doses compared to 177Lu-labeled Glu-ureide-based PSMA inhibitory peptides. To obtain a 99mTc-/177Lu-scFvD2B theranostic pair, this research aimed to synthesize and biochemically characterize a novel 99mTc-scFvD2B radiotracer. The scFvD2B-Tag and scFvD2B antibody fragments were produced and purified. Then, two HYNIC derivatives, HYNIC-Gly-Gly-Cys-NH2 (HYNIC-GGC) and succinimidyl-HYNIC (S-HYNIC), were used to conjugate the scFvD2B-Tag and scFvD2B isoforms, respectively. Subsequently, chemical characterization, immunoreactivity tests (affinity and specificity), radiochemical purity tests, stability tests in human serum, cellular uptake and internalization in LNCaP(+), PC3-PIP(++) or PC3(-) PCa cells of the resulting unlabeled HYNIC-scFvD2B conjugates (HscFv) and 99mTc-HscFv agents were performed. The results showed that incorporating HYNIC as a chelator did not affect the affinity, specificity or stability of scFvD2B. After purification, the radiochemical purity of 99mTc-HscFv radiotracers was greater than 95%. A two-sample t-test of 99mTc-HscFv1 and 99mTc-HscFv1 uptake in PC3-PIP vs. PC3 showed a p-value < 0.001, indicating that the PSMA receptor interaction of 99mTc-HscFv agents was statistically significantly higher in PSMA-positive cells than in the negative controls. In conclusion, the results of this research warrant further preclinical studies to determine whether the in vivo pharmacokinetics and tumor uptake of 99mTc-HscFv still offer sufficient advantages over HYNIC-conjugated peptides to be considered for SPECT/PSMA imaging.

Can MDCT Enhancement Patterns Be Helpful in Differentiating Secretory from Non-Functional Adrenal Adenoma?

Background and Objectives: Primary adrenal tumors (AT) are a heterogeneous group of neoplasms due to their functional heterogeneity, which results in the diverse clinical presentation of these tumors. The purpose of this study was to examine cross-sectional imaging characteristics using multi-detector computed tomography (MDCT) to provide insight into the lesion characterization and functional status of these tumors. The radionuclide imaging using Technetium-99m radiolabeled hydrazinonicotinylacid-d-phenylalanyl1-tyrosine3-octreotide (99mTc-HYNIC-TOC), was also used in the diagnostic evaluation of these tumors. Materials and Methods: This cross-sectional study included 50 patients with confirmed diagnoses of AT (21 hormone-secreting and 29 non-functional) at the University Clinical Center, Kragujevac, Serbia, during the 2019-2022 year period. The morphological and dynamic characteristics using MDCT were performed, using qualitative, semi-quantitative, and quantitative analysis. Absolute washout (APW) and relative washout (RPW) values were also calculated. A semi-quantitative analysis of all visual findings with 99mTc-HYNIC-TOC was performed to compare the tumor to non-tumor tracer uptake. Results: A statistically significant difference was found in the MDCT values in the native phase (p < 0.05), the venous phase (p < 0.05), and the delayed phase (p < 0.001) to detect the existence of adrenal tumors. Most of these functional adrenocortical lesions (n = 44) can be differentiated using the delayed phase (p < 0.05), absolute percentage washout (APW) (p < 0.05), and relative percentage washout (RPW) (p < 0.001). Furthermore, 99mTc-HYNIC-TOC could have a high diagnostic yield to detect adrenal tumor existence (p < 0.001). There is a positive correlation between radionuclide imaging scan and APW to detect all AT (p < 0.01) and adrenocortical adenomas as well (p < 0.01). Conclusions: The results can be very helpful in a diagnostic algorithm to quickly and precisely diagnose the expansive processes of the adrenal glands, as well as to learn about the advantages and limitations of the mentioned imaging modalities.

Diagnostic performance of 99mTc-HYNIC-PSMA SPECT/CT for biochemically recurrent prostate cancer after radical prostatectomy.

Objectives: 99mTc-HYNIC-PSMA is a novel technetium-99m-labeled small-molecule inhibitor of prostate-specific membrane antigen (PSMA) for detection of prostate cancer. The present study investigated the diagnostic yield of 99mTc-HYNIC-PSMA Single photon emission computed tomography (SPECT)/CT in 147 patients with biochemically recurrent prostate cancer after radical prostatectomy. Methods: 147 patients with biochemical relapse after radical prostatectomy were finally eligible for this retrospective analysis. The median prostate-specific antigen (PSA) level was 8.26 ng/mL (range, 0.22-187.40 ng/mL). Of the 147 patients, 72 patients received androgen deprivation therapy (ADT) at least 6 months before the 99mTc-HYNIC-PSMA SPECT/CT. All patients underwent planar whole-body scans and subsequent SPECT/CT of the thoracic and abdominal regions after intravenous injection of 705 ± 70 MBq of 99mTc-HYNIC-PSMA. Images were evaluated for the presence and location of PSMA-positive lesions, in which SUVmax were also measured. Detection rates were stratified according to PSA levels, ADT and Gleason scores. The relationships between SUVmax and clinical characteristics were analyzed using univariate and multivariable linear regression models for patients with positive findings. Results: Of the 147 patients, 99mTc-HYNIC-PSMA SPECT/CT revealed at least one positive lesion in 118 patients with a high detection rate (80.3%). The detection rates were 48.6% (17/35), 85.1% (40/47), 92.1% (35/38), and 96.3% (26/27) at PSA levels of greater than 0.2 to 2, greater than 2 to 5, greater than 5 to 10, and greater than 10 ng/mL, respectively. PSMA SPECT/CT indicated local recurrence, lymph node metastases, bone metastases, and visceral metastases in 14 (9.5%), 73 (49.7%), 48 (32.7%) and 3 (2.0%) patients. The detection rates of local recurrence and metastasis increased with increasing PSA levels. The detection rate was higher in patients treated with ADT than those without (90.3% vs. 70.7%; P =0.0029). In patients with Gleason scores ≥8, detection rate was slightly higher than those with ≤7 (81.7% vs. 78.5%), but not statistically significant (P = 0.6265). Multivariable linear regression analysis showed a significant correlation of PSA levels and ADT with SUVmax (P=0.0005 and P=0.0397). Conclusions: 99mTc-HYNIC-PSMA SPECT/CT offers high detection rates for biochemically recurrent prostate cancer after radical prostatectomy. The detection rate and SUVmax were positively correlated with PSA levels and ADT.