99mTc-EDDA/HYNIC-TOC is a New Opportunity in Neuroendocrine Tumors of the Lung (and in other Malignant and Benign Pulmonary Diseases)

Next-level precision medicine: why the theragnostic approach is the future

Theragnostics represents one of the most innovative fields of precision medicine with a huge potential in the field of oncology in the next years. The use of a pair of selective radiopharmaceuticals for cellular receptors, used for diagnostic and therapeutic purposes (PRRT), finds applications in the Neuroendocrine tumors and metastatic Castration-Resistant prostate cancer (mCRPC) thanks, respectively, to somatostatin receptor agonists and PSMA-based peptides. Further evolutions of theragnostics will be possible to the radioimmunoconjugates used both in the diagnostic (Immuno-PET) and in the therapeutic fields (radioimmunotherapy). It is evident that in the "omics-era," theragnostics could become a necessary method, not only in order to improve our knowledge of tumor biology, but also, to find more and more targeted therapies in a multidisciplinary context and in a tailor-based approach.

Role of Pure Technetium Chemistry: Are There Still Links to Applications in Imaging?

The discovery and development of new 99mTc-based radiopharmaceuticals or labeled drugs in general is based on innovative, pure chemistry and subsequent, application-targeted research. This was the case for all currently clinically applied imaging agents. Most of them were market-introduced some 20 years ago, and the few more recent ones are based on even older chemistry, albeit technetium chemistry has made substantial progress over the last 20 years. This progress though is not mirrored by new molecular imaging agents and is even accompanied by a steady decrease in the number of groups active in pure and applied technetium chemistry, a contrast to the trends in most other fields in which d-elements play a central role. The decrease in research with technetium has been partly counterbalanced by a strong increase of research activities with homologous, cold rhenium compounds for therapy, disclosing in the future eventually a quite unique opportunity for theranostics. This Viewpoint analyzes the pathways that led to radiopharmaceuticals in the past and their underlying fundamental contributions. It attempts to tackle the question of why new chemistry still does not lead to new imaging agents, i.e., the question of whether pure technetium chemistry is still needed at all.

Breast Imaging Physics in Mammography (Part I)

Breast cancer is the most frequently diagnosed neoplasm in women in Italy. There are several risk factors, but thanks to screening and increased awareness, most breast cancers are diagnosed at an early stage when surgical treatment can most often be conservative and the adopted therapy is more effective. Regular screening is essential but advanced technology is needed to achieve quality diagnoses. Mammography is the gold standard for early detection of breast cancer. It is a specialized technique for detecting breast cancer and, thus, distinguishing normal tissue from cancerous breast tissue. Mammography techniques are based on physical principles: through the proper use of X-rays, the structures of different tissues can be observed. This first part of the paper attempts to explain the physical principles used in mammography. In particular, we will see how a mammogram is composed and what physical principles are used to obtain diagnostic images.

Clinical validation and diagnostic accuracy of 99mTc-EDDA/HYNIC-TOC compared to 111In-DTPA-octreotide in patients with neuroendocrine tumours: the LACOG 0214 study

99mTc-EDDA/HYNIC-TOC is an easily available and cheaper radionuclide that could be used for somatostatin-receptor-based imaging of neuroendocrine tumours (NETs). We aimed to evaluate the diagnostic performance of 99mTc-EDDA/HYNIC-TOC compared to111In-DTPA-octreotide in patients (pts) with NETs. We performed a prospective diagnostic study including pts with biopsy-confirmed NET and at least one visible lesion at conventional imaging. Two independent nuclear medicine physicians evaluated pts who underwent 99mTc and 111In scans and images. The primary outcome was comparative diagnostic accuracy of 99mTc and 111In. Secondary outcomes include safety. Nine pts were included and performed 14 paired scans. Overall, 126 lesions were identified. 99mTc demonstrated superior sensitivity both when all images were analysed (93.7, 95% CI 88.1% - 96.8% versus 74.8%, 95% CI 66.6 - 81.6%, p < 0.001) and when liver-specific images were analysed (97.8%, 95% CI 92.7% - 99.5% versus 85.1%, 95% CI 76.6% - 91.0%, p < 0.001). 99mTc was also associated with a lower negative likelihood ratio (LR) (0.002, 95% CI 0.009 - 0.1 versus 0.19, 95% CI 0.12 - 0.42, p = 0.009) when evaluating hepatic lesions. Adverse events happened in 3 pts after 111In and in 2 pts after 99mTc, all grade 1. The 99mTc demonstrated a higher sensitivity overall and a better negative LR in liver-specific images compared to 111In in pts with NETs. Our findings suggest that 99mTc is an alternative to 111In and is especially useful in ruling out liver metastases. NCT02691078.

A Systematic Review on Combined [18F]FDG and 68Ga-SSA PET/CT in Pulmonary Carcinoid

Pulmonary carcinoids (PCs) are part of a spectrum of well-differentiated neuroendocrine neoplasms (NENs) and are classified as typical carcinoid (TC) and atypical carcinoid (AC). TC differ from AC not only for its histopathological features but also for its "functional imaging pattern" and prognosis. ACs are more undifferentiated and characterized by higher aggressiveness. Positron emission tomography/computed tomography (PET/CT) with somatostatin analogs (SSA) labeled with Gallium-68 (⁶⁸Ga-DOTA-TOC, ⁶⁸Ga-DOTA-NOC, ⁶⁸Ga-DOTA-TATE) has widely replaced conventional imaging with gamma camera using ¹¹¹In- or ^99mTc-labelled compounds and represents now the gold standard for diagnosis and management of NENs. In this setting, as already described for gastro-entero-pancreatic NENs, ¹⁸F-Fluorodeoxiglucose ([¹⁸F]FDG) in addition to ⁶⁸Ga-SSA can play an important role in clinical practice, particularly for ACs that show a more aggressive behavior compared to TCs. The aim of this systematic review is to analyze all original studies collected from the PubMed and Scopus databases regarding PCs in which both ⁶⁸Ga-SSA PET/CT and [¹⁸F]FDG PET/CT were performed in order to evaluate the clinical impact of each imaging modality. The following keywords were used for the research: "¹⁸F, ⁶⁸Ga and (bronchial carcinoid or carcinoid lung)". A total of 57 papers were found, of which 17 were duplicates, 8 were reviews, 10 were case reports, and 1 was an editorial. Of the remaining 21 papers, 12 were ineligible because they did not focus on PC or did not compare ⁶⁸Ga-SSA and [¹⁸F]FDG. We finally retrieved and analyzed nine papers (245 patients with TCs and 110 patients with ACs), and the results highlight the importance of the combined use of ⁶⁸Ga-SSA and [¹⁸F]FDG PET/CT for the correct management of these neoplasms.

Radiomics in Breast Imaging: Future Development

Breast cancer is the most common and most commonly diagnosed non-skin cancer in women. There are several risk factors related to habits and heredity, and screening is essential to reduce the incidence of mortality. Thanks to screening and increased awareness among women, most breast cancers are diagnosed at an early stage, increasing the chances of cure and survival. Regular screening is essential. Mammography is currently the gold standard for breast cancer diagnosis. In mammography, we can encounter problems with the sensitivity of the instrument; in fact, in the case of a high density of glands, the ability to detect small masses is reduced. In fact, in some cases, the lesion may not be particularly evident, it may be hidden, and it is possible to incur false negatives as partial details that may escape the radiologist's eye. The problem is, therefore, substantial, and it makes sense to look for techniques that can increase the quality of diagnosis. In recent years, innovative techniques based on artificial intelligence have been used in this regard, which are able to see where the human eye cannot reach. In this paper, we can see the application of radiomics in mammography.

Integration of molecular imaging in the personalized approach to neuroendocrine tumors

NETs lesions can be difficult to characterize with conventional anatomic imaging (CT and MRI). Functional imaging techniques, and especially PET imaging, are very useful for detecting small neuroendocrine tumors that would not be seen with other techniques. The role of nuclear medicine in the localization, staging, restaging, treatment and monitoring of neuroendocrine tumors (NETs) has become progressively more relevant due to: the availability of tracers on new targets, tracers for positron emission tomography (PET); the development of cyclotrons and generators that allow this availability; as well as to hybrid systems (SPECT/CT, PET/CT and PET/MRI) that, by joining the functional and anatomical image, improve the quality of the images. Teragnosis, a new emerging therapy, in NET used receptor-mediated or nonreceptor- mediated mechanism to facilitate penetration and high-affinity binding between the radiopharmaceutical and the tumor cell. Teragnosis offers the possibility of personalized targeted radionuclide therapy.

The New Radiolabeled Peptide 99mTcEDDA/HYNIC-TOC: Is It a Feasible Choice for Diagnosing Gastroenteropancreatic NETs?

(1) Background: The aim of our study is to reveal the advantages and limitations of the use of 99mTcEDDA/HYNIC-TOC (Tektrotyd®, Polatom) in the diagnosis of gastroenteropancreatic neuroendocrine tumors and to compare our results with the values obtained for 111In-pentetreotide and 68Ga-DOTA-peptides, routinely used in medical practice. (2) Methods: This retrospective monocentric study included 173 patients with gastroenteropancreatic neuroendocrine tumors who underwent 99mTcEDDA/HYNIC-TOC scans 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. Physiological and abnormal uptake were established by two experienced physicians and, based on the obtained results, sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated. (3) Results: Our method presented a sensitivity of 90.5%, a specificity of 71.9%, and an accuracy of 84.3%, with a positive predictive value of 86.7% and a negative predictive value of 78.8%. (4) Conclusions: 99mTc-EDDA/HYNIC-TOC, a receptor-based radiopharmaceutical, could represent a competitor for 68Ga-labeled peptides in the diagnosis and management of patients with gastroenteropancreatic neuroendocrine tumors. Our results show a lower sensitivity (90.5%) than 68Ga-DOTA-peptides, but with great specificity, accuracy, positive, and negative predictive values.

Somatostatin and Somatostatin Receptors: From Signaling to Clinical Applications in Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) are heterogeneous neoplasms which arise from neuroendocrine cells that are distributed widely throughout the body. Although heterogenous, many of them share their ability to overexpress somatostatin receptors (SSTR) on their cell surface. Due to this, SSTR and somatostatin have been a large subject of interest in the discovery of potential biomarkers and treatment options for the disease. The aim of this review is to describe the molecular characteristics of somatostatin and somatostatin receptors and its application in diagnosis and therapy on patients with NENs as well as the use in the near future of somatostatin antagonists.

Improved Personalised Neuroendocrine Tumours' Diagnosis Predictive Power by New Receptor Somatostatin Image Processing Quantification

Although neuroendocrine tumours (NETs) are intensively studied, their diagnosis and consequently personalised therapy management is still puzzling due to their tumoral heterogeneity. In their theragnosis algorithm, receptor somatostatin scintigraphy takes the central place, the diagnosis receptor somatostatin analogue (RSA) choice depending on laboratory experience and accessibility. However, in all cases, the results depend decisively on correct radiotracer tumoral uptake quantification, where unfortunately there are still unrevealed clues and lack of standardization. We propose an improved method to quantify the biodistribution of gamma-emitting RSA, using tissular corrected uptake indices. We conducted a bi-centric retrospective study on 101 patients with different types of NETs. Three uptake indices obtained after applying new corrections to areas of interest drawn for the tumour and for three reference organs (liver, spleen and lung) were statistically analysed. For the corrected pathological uptake indices, the results showed a significant decrease in the error of estimating the occurrence of errors and an increase in the diagnostic predictive power for NETs, especially in the case of lung-referring corrected index. In conclusion, these results support the importance of corrected uptake indices use in the analysis of ^99mTcRSA biodistribution for a better personalised diagnostic accuracy of NETs patients.

From the Magic Bullet to Theragnostics: Certitudes and Hypotheses, Trying to Optimize the Somatostatin Model

Simple Summary

In oncology, the hypothetical “perfect magic bullet” should have a specific target on tumor cells which allows one to target only the tumor, in the absence of uptake in normal and/or non-neoplastic cells. Theragnostics is a strategy that strictly combines diagnosis and therapy, which creates the conditions for an “a priori” definition of an effective therapeutic effect. The most complete theragnostic and “magic bullet” experiences in clinical practice are those associated with radioiodine and somatostatin model. In this paper, we analyze whether it could be possible to improve present clinical results, further extending the survival of a wider number of patients, expanding the recruitment criteria to other types of pathology, and improving the quality of life. The ultimate goal is to transform the theragnostic strategy based on the somatostatin model into a curative therapy in the highest possible number of patients.

Abstract

The first “theragnostic model”, that of radioiodine, was first applied both in diagnosis and therapy in the 1940s. Since then, many other theragnostic models have been introduced into clinical practice. To bring about the closest pharmacokinetic connection, the radiocompound used for diagnosis and therapy should be the same, although at present this is rarely applicable. Today, a widely applied and effective model is also the “DOTA-Ga-68/Lu-177”, used with success in neuroendocrine tumors (NET). In this paper, we analyze the necessary steps from the in vitro evaluation of a target to the choice of radionuclide and chelate for therapy up to in vivo transition and clinical application of most employed radiocompounds used for theragnostic purposes. Possible future applications and strategies of theragnostic models are also highlighted.