Investigation of the Effect on the Albumin Binding Moiety for the Pharmacokinetic Properties of 68Ga-, 205/206Bi-, and 177Lu-Labeled NAPamide-Based Radiopharmaceuticals

Although radiolabeled alpha-melanocyte stimulating hormone-analogue NAPamide derivatives are valuable melanoma-specific diagnostic probes, their rapid elimination kinetics and high renal uptake may preclude them from being used in clinical settings. We aimed at improving the pharmacokinetics of radiolabeled DOTA-NAPamide compounds by incorporating a 4-(p-iodo-phenyl)-butanoic acid (IPB) into the molecules. Followed by 68Ga-, 205/206Bi-, and 177Lu-labelling, the radiopharmaceuticals ([68Ga]Ga-DOTA-IPB-NAPamide, [205/206Bi]Bi-DOTA-IPB-NAPamide, [177Lu]Lu-DOTA-IPB-NAPamide) were characterized in vitro. To test the imaging behavior of the IPB-containing probes, B16F10 tumor-bearing C57BL/6 mice were subjected to in vivo microPET/microSPECT/CT imaging and ex vivo biodistribution studies. All tracers were stable in vitro, with radiochemical purity exceeding 98%. The use of albumin-binding moiety lengthened the in vivo biological half-life of the IPB-carrying radiopharmaceuticals, resulting in elevated tumor accumulation. Both [68Ga]Ga-DOTA-IPB-NAPamide (5.06 ± 1.08 %ID/g) and [205/206Bi]Bi-DOTA-IPB-NAPamide (4.50 ± 0.98 %ID/g) exhibited higher B16F10 tumor concentrations than their matches without the albumin-binding residue ([68Ga]Ga-DOTA-NAPamide and [205/206Bi]Bi-DOTA-NAPamide: 1.18 ± 0.27 %ID/g and 3.14 ± 0.32; respectively), however; the large amounts of off-target radioactivity do not confirm the benefits of half-life extension for short-lived isotopes. Enhanced [177Lu]Lu-DOTA-IPB-NAPamide tumor uptake even 24 h post-injection proved the advantage of IPB-based prolonged circulation time regarding long-lived radionuclides, although the significant background noise must be addressed in this case as well.

Evaluation of iodine-123-labeled metaiodobenzylguanidine single-photon emission computed tomography/computed tomography based on the International Society of Pediatric Oncology Europe Neuroblastoma score in children with neuroblastoma

Background

This study sought to examine whether iodine-123-labeled metaiodobenzylguanidine (¹²³I-MIBG) single-photon emission computed tomography/computed tomography (SPECT/CT), which is based on the International Society of Pediatric Oncology Europe Neuroblastoma (SIOPEN) score, could improve the diagnostic efficiency of children with neuroblastoma (NB), and to compare the diagnostic ability of minimal residual disease (MRD) detection and ¹²³I-MIBG SPECT/CT.

Methods

We retrospectively analyzed 238 scans of patients who underwent ¹²³I-MIBG SPECT/CT at the Department of Nuclear Medicine, Beijing Friendship Hospital, from January 2021 to December 2021. The diagnostic study was not registered with a clinical trial platform, and the study protocol was not published. The standard was established based on pathology, other relevant imaging examinations, and follow-up. The SIOPEN scores were calculated separately based on planar and tomographic imaging.

Results

In a comparison to the standard mentioned in the method, the diagnostic accuracy of planar and tomographic imaging was 151 of 238 (63.5%) and 228 of 238 (95.8%), respectively, and the κ values of the SIOPEN score were 0.468 and 0.855 (P<0.001), respectively. The SIOPEN scores differed significantly among the various subgroups. The polymerase chain reaction (PCR) method used to detect the bone marrow PHOX2B gene was able to find bone/bone marrow metastases (P=0.024, κ=0.282), while the flow cytometry (FCM) assay method was not statistically significant (P=0.417, κ=0.065).

Conclusions

¹²³I-MIBG SPECT/CT, which relies on the semiquantitative assessment of the SIOPEN score, is of clinical importance in the management of pediatric NB. MRD detection can be used to detect early metastasis and recurrence in the bone or bone marrow; however, ¹²³I-MIBG SPECT/CT has better diagnostic value. We intend to conduct further investigations on their prognostic value in the future.

A Review of Nuclear Medicine Approaches in the Diagnosis and the Treatment of Gynecological Malignancies

Nuclear medicine is defined as the diagnosis and the treatment of disease using radiolabeled compounds known as radiopharmaceuticals. Single-photon emission computed tomography/computed tomography (SPECT/CT) and positron emission tomography/computer tomography (PET/CT) based radiopharmaceuticals have proven reliable in diagnostic imaging in nuclear medicine and cancer treatment. One of the most critical cancers that also relies on an early diagnosis is gynecological cancer. Given that approximately 25% of all cancers in developing countries are a subset of gynecological cancer, investigating this cancer subtype is of significant clinical worth, particularly in light of its high rate of mortality. With accurate identification of high grade distant abdominal endometrial cancer as well as extra abdominal metastases, 18F-Fluorodeoxyglucose ([18F]FDG) PET/CT imaging is considered a valuable step forward in the investigation of gynecological cancer. Considering these factors, [18F]FDG PET/CT imaging can assist in making management of patient therapy more feasible. In this literature review, we will provide a short overview of the role of nuclear medicine in the diagnosis of obstetric and gynecological cancers.

Comparison of the Uptake of Hepatocellular Carcinoma on Pre-Therapeutic MDCT, CACT, and SPECT/CT, and the Correlation with Post-Therapeutic PET/CT in Patients Undergoing Selective Internal Radiation Therapy

(1) Background: To comparatively analyze the uptake of hepatocellular carcinoma (HCC) on pre-therapeutic imaging modalities, the arterial phase multi-detector computed tomography (MDCT), the parenchymal phase C-arm computed tomography (CACT), the Technetium⁹⁹m-macroaggregates of human serum albumin single-photon emission computed tomography/computed tomography (SPECT/CT), and the correlation to the post-therapeutic Yttrium⁹⁰ positron emission tomography/computed tomography (PET/CT) in patients with selective internal radiation therapy (SIRT). (2) Methods: Between September 2013 and December 2016, 104 SIRT procedures were performed at our institution in 74 patients with HCC not suitable for curative surgery or ablation. Twenty-two patients underwent an identical sequence of pre-therapeutic MDCT, CACT, SPECT/CT, and post-therapeutic PET/CT with a standardized diagnostic and therapeutic protocol. In these 22 patients, 25 SIRT procedures were evaluated. The uptake of the HCC was assessed using tumor-background ratio (TBR). Therefore, regions of interest were placed on the tumor and the adjacent liver tissue on MDCT (TBR^MDCT), CACT (TBR^CACT), SPECT/CT (TBR^SPECT/CT), and PET/CT (TBR^PET/CT). Comparisons were made with the Friedman test and the Nemenyi post-hoc test. Correlations were analyzed using Spearman’s Rho and the Benjamini–Hochberg method. The level of significance was p < 0.05. (3) Results: TBR on MDCT (1.4 ± 0.3) was significantly smaller than on CACT (1.9 ± 0.6) and both were significantly smaller compared to SPECT/CT (4.6 ± 2.0) (pFriedman-Test < 0.001; pTBR^MDCT/TBR^CACT = 0.012, pTBR^MDCT/TBR^SPECT/CT < 0.001, pTBR^CACT/TBR^SPECT/CT < 0.001). There was no significant correlation of TBR on MDCT with PET/CT (rTBR^MDCT/TBR^PET/CT = 0.116; p = 0.534). In contrast, TBR on CACT correlated to TBR on SPECT/CT (rTBR^CACT/TBR^SPECT/CT = 0.489; p = 0.004) and tended to correlate to TBR on PET/CT (rTBR^CACT/TBR^PET/CT =0.365; p = 0.043). TBR on SPECT/CT correlated to TBR on PET/CT (rTBR^SPECT/CT/TBR^PET/CT = 0.706; p < 0.001) (4) Conclusion: The uptake assessment on CACT was in agreement with SPECT/CT and might be consistent with PET/CT. In contrast, MDCT was not comparable to CACT and SPECT/CT, and had no correlation with PET/CT due to the different application techniques. This emphasizes the value of the CACT, which has the potential to improve the dosimetric assessment of the tumor and liver uptake for SIRT.