99mTc-HYNIC-TOC imaging in the evaluation of pancreatic masses which are potential neuroendocrine tumors

Current progress and remaining challenges of peptide-drug conjugates (PDCs): next generation of antibody-drug conjugates (ADCs)?

Drug conjugates have emerged as a promising alternative delivery system designed to deliver an ultra-toxic payload directly to the target cancer cells, maximizing therapeutic efficacy while minimizing toxicity. Among these, antibody-drug conjugates (ADCs) have garnered significant attention from both academia and industry due to their great potential for cancer therapy. However, peptide-drug conjugates (PDCs) offer several advantages over ADCs, including more accessible industrial synthesis, versatile functionalization, high tissue penetration, and rapid clearance with low immunotoxicity. These factors position PDCs as up-and-coming drug candidates for future cancer therapy. Despite their potential, PDCs face challenges such as poor pharmacokinetic properties and low bioactivity, which hinder their clinical development. How to design PDCs to meet clinical needs is a big challenge and urgent to resolve. In this review, we first carefully analyzed the general consideration of successful PDC design learning from ADCs. Then, we summarised the basic functions of each component of a PDC construct, comprising of peptides, linkers and payloads. The peptides in PDCs were categorized into three types: tumor targeting peptides, cell penetrating peptide and self-assembling peptide. We then analyzed the potential of these peptides for drug delivery, such as overcoming drug resistance, controlling drug release and improving therapeutic efficacy with reduced non-specific toxicity. To better understand the potential druggability of PDCs, we discussed the pharmacokinetics of PDCs and also briefly introduced the current PDCs in clinical trials. Lastly, we discussed the future perspectives for the successful development of an oncology PDC. This review aimed to provide useful information for better construction of PDCs in future clinical applications.

Microcystic Serous Cystadenoma Masquerading as Pancreatic Neuroendocrine Tumor on 99m Tc-HYNIC-TOC SPECT/CT

ABSTRACT

We present 99m Tc-HYNIC-TOC SPECT/CT findings in a case of microcystic serous cystadenoma of the pancreatic head. The pancreatic tumor showed intense 99m Tc-HYNIC-TOC uptake mimicking neuroendocrine tumor on SPECT/CT. This case indicates that microcystic serous cystadenoma should be included in the differential diagnosis of 99m Tc-HYNIC-TOC-avid pancreatic masses.

Adrenal Castleman Disease on 99mTc-HYNIC-TOC Scan and FDG PET/CT

Adrenal Castleman disease is very rare. We reported image findings of a right adrenal mass in a 75-year-old man on Tc-HYNIC-TOC scan and FDG PET/CT. There was obviously elevated Tc-HYNIC-TOC activity, but the intensity of FDG activity was remarkable. Pheochromocytoma was initially suspected. However, pathology from resected specimen showed adrenal Castleman disease.

99mTc-Labeled Native RBC Scintigraphy in Distinguishing Polysplenia From Abdominal Masses in a Patient With Situs Inversus Totalis

A 39-year-old previously healthy woman presented possible hematuria. An ultrasound examination showed right adrenal mass and suggested pheochromocytoma. A Tc-HYNIC-TOC SPECT/CT was performed, which incidentally detected situs inversus totalis and suspicion of polysplenia without definite normal spleen in the right upper abdomen. In order to differentiate the polysplenia from other etiologies, a heat-damaged Tc RBC scintigraphy was performed. The images showed significant activity in the multiple soft tissue nodules in the posterior right abdomen, consistent with ectopic polysplenia.

State of the Art and Recent Developments of Radiopharmaceuticals for Pancreatic Neuroendocrine Tumors Imaging

Background:

Neuroendocrine Tumors (NETs) are relatively rare tumors, mainly originating from the digestive system, that tend to grow slowly and are often diagnosed when metastasised. Surgery is the sole curative option but is feasible only in a minority of patients. Among them, pancreatic neuroendocrine tumors (pancreatic NETs or pNETs) account for less than 5% of all pancreatic tumors. Viable therapeutic options include medical treatments such as biotherapies and more recently Peptide Receptor Radionuclide Therapies (PRRT) with radiolabeled somatostatin analogues. Molecular imaging, with main reference to PET/CT, has a major role in patients with pNETs.

Objective:

The overexpression of specific membrane receptors, as well as the ability of cells to take up amine precursors in NET, have been exploited for the development of specific targeting imaging agents.

Methods:

SPECT/CT and PET/CT with specific isotopes such as [68Ga]-1,4,7,10-tetra-azacyclododecane- N,N’,N’’,N’’’-tetra-acetic acid (DOTA)-somatostatin analogs, [18F]-FDG and [18F]-fluorodopa have been clinically explored.

Results:

To overcome the limitations of SSTR imaging, interesting improvements are connected with the availability of new radiotracers, activating with different mechanisms compared to somatostatin analogues, such as glucagon-like peptide 1 receptor (GLP-1 R) agonists or antagonists.

Conclusion:

This paper shows an overview of the RPs used so far in the imaging of pNETs with insight on potential new radiopharmaceuticals currently under clinical evaluation.

Increased Activity Due to Fractures Does Not Significantly Affect the Accuracy of 68Ga-DOTATATE PET/CT in the Detection of Culprit Tumor in the Evaluation of Tumor-Induced Osteomalacia

OBJECTIVE

Ga-DOTATATE PET/CT is currently the most common imaging modality in localizing culprit tumors, which can result in tumor-induced osteomalacia (TIO). Fracture, which is one of the most common consequences of the TIO, can also lead to increased Ga-DOTATATE activity and potentially affect the accuracy of Ga-DOTATATE PET/CT imaging. The aim of this investigation is to evaluate whether the increased Ga-DOTATATE activity at the sites of the fracture will cause interpretation difficulty in the localizing the culprit tumor causing TIO.

METHOD

The images of Ga-DOTATATE PET/CT scan from a total of 54 patients who had multiple foci of increased Ga-DOTATATE PET/CT on PET/CT were retrospectively analyzed. Not only was the intensity of the activity on PET but also the appearance of the activity on CT taken into consideration when the interpretation of the images occurred. The results from imaging analysis were compared with the clinical chart record. All patients had tentative clinical diagnosis of TIO.

RESULTS

The causative tumors in 53 patients were eventually identified. In 1 patient, the causative tumor was not identified. Among the 53 patients with confirmed TIO, 52 tumors were accurately localized.

CONCLUSIONS

Mild activity at the sites of fracture is not a major challenging factor in the interpretation of Ga-DOTATATE PET/CT in the evaluation of TIO when both intensity on PET and morphology on CT were assessed.

Clinical application of 99mTc-HYNIC-TOC SPECT/CT in diagnosing and monitoring of pancreatic neuroendocrine neoplasms

OBJECTIVE

Our aim of this research was to determine the value of SPECT/CT with ^99mTc-HYNIC-TOC for evaluation of the pancreatic masses which were suspected as neuroendocrine neoplasms and follow-up of patients with pancreatic neuroendocrine neoplasms.

METHODS

We retrospectively analyzed 184 patients who performed ^99mTc-HYNIC-TOC SPECT/CT. All the patients were divided into two groups: one for assessment of diagnostic efficiency for pancreatic suspected masses (n = 140) and another for monitoring recurrence after surgery (n = 44). The image findings acquired at 2 h postinjection were compared to final diagnoses from pathological results and clinical follow-up. Then, the correlation between ratios of tumor-to-background (TBR) and tumor grade was analyzed.

RESULTS

In group 1, 95/140 (67.9%) patients were confirmed as neuroendocrine neoplasms including 85 neuroendocrine tumors and 10 neuroendocrine carcinomas. Patient-based analysis showed that the sensitivity, specificity and accuracy of diagnosing neuroendocrine neoplasms with SPECT/CT were 81.1, 84.4 and 82.1%. There was significant difference of TBRs among G1, G2 and G3 (F = 3.175, P = 0.048). In group 2, 22/44 (50.0%) patients occurred metastasis mainly in liver. The sensitivity, specificity and accuracy of monitoring recurrence were 87.0, 100 and 93.2%.

CONCLUSIONS

^99mTc-HYNIC-TOC SPECT/CT is a reliable method of diagnosing and monitoring of pancreatic neuroendocrine neoplasms, especially neuroendocrine tumors.

A Rare Case of Retroperitoneal Follicular Dendritic Cell Sarcoma Identified by 99mTc-HYNIC-TOC SPECT/CT

Follicular dendritic cell sarcoma is a very rare neoplasm, which is not lymphoma, but originates from a type of immune cells called follicular dendritic cells. We presented a 37-year-old woman who has suffered from obstructive jaundice, weight loss and right upper abdominal pain for 2 months. The contrast CT revealed masses located in the region of pancreatic head and lots of enlarged retroperitoneal lymph nodes, both of which were enhanced on the artery phase of CT images. Meanwhile, Tc-HYNIC-TOC SPECT/CT revealed high activity in the corresponding lesions. After biopsy, the masses were pathologically confirmed as retroperitoneal follicular dendritic cell sarcoma.

Incremental value of 99mTc-HYNICTOC SPECT/CT over whole-body planar scintigraphy and SPECT in patients with neuroendocrine tumours

Aim: The aim of this study was to evaluate the additional value of 99mTc-HYNIC-TOC SPECT/CT over planar whole-body (WB) scintigraphy and SPECT alone in the detection and accurate localisation of neuroendocrine tumour (NET) lesions. Methods: This study included 65 patients with a definitive histological diagnosis of NET prior to scintigraphy. Planar WB scintigraphy, SPECT, and SPECT/CT images were acquired at 4 h postadministration of 670 MBq 99mTc-HYNIC- TOC. Additional SPECT images at 10 min after tracer administration were also acquired. Clinical and imaging follow-up findings were considered as the reference standards (minimum follow-up period, 15 months). Patient and lesion-based analyses of the efficacies of the imaging modalities were performed. Results: While 38 patients exhibited metastasis of NETs, 27 presented no evidence of metastasis. Upon patient- based analysis, the sensitivity and specificity of SPECT/CT were found to be 88.9 and 79.3 %, respectively. The diagnostic accuracies of WB scintigraphy, 4h-SPECT, and SPECT/CT were 72.3, 73.8, and 84.6 %o, respectively. The area under curve (AUC) value for SPECT/CT (0.84) was the highest, followed by those for 4h-SPECT (0.75) and WB scintigraphy (0.74). The accuracy and AUC values of SPECT/CT were significantly better compared to those of WB scintigraphy (p < 0.001), 10 min-SPECT (p < 0.001), and 4 h-SPECT (p = 0.001). The findings of SPECT/CT led to the change in treatment plan of 11 patients (16.9 %o). Conclusion: The sensitivity and diagnostic accuracy of SPECT/CT in the evaluation of NET lesions outperforms planar WB imaging or SPECT alone.

Surgery management for sporadic small (≤2 cm), non-functioning pancreatic neuroendocrine tumors: a consensus statement by the Chinese Study Group for Neuroendocrine Tumors (CSNET)

The incidence of small (≤2 cm), non-functioning pancreatic neuroendocrine tumors (NF-pNETs) increased in the last decades. Before making appropriate strategy for patients with NF-pNETs ≤2 cm, pathological confirmation is vital. Incidentally diagnosed, sporadic small NF-pNETs may bring aggressive behavior and poor prognosis, such as extrapancreatic extension, lymph nodal metastasis, distant metastasis and recurrence, even causing disease-related death. Understanding and formulating an appropriate strategy for the patients with sporadic small, non-functioning pancreatic neuroendocrine tumors have been controversial for some time. Although several studies have reported that patients with NF-pNETs ≤2 cm had less rate of malignant behavior compared with larger ones (>2 cm); and the surgery approach may leading to surgery-related pancreatic complications; but there is still a lack of level I evidence to convince surgeons to abandon all cases with sporadic small NF-pNETs. Based on an updated literature search and review, the members of the Chinese Study Group for Neuroendocrine Tumors (CSNET) from high-volume centers have reached a consensus on the issue of the management strategy for the sporadic small NF-pNETs. We recommend that, except for some selected patients with NF-pNETs <1 cm, incidentally discovered and unacceptable surgical risks, all others with NF-pNETs ≤2 cm should undergo tumor resection with lymph node dissection or at least lymph node sampling and careful postoperative surveillance.