Usefulness of 64Cu-ATSM in head and neck cancer: a preliminary prospective study

Impact of human serum albumin on CuII and ZnII complexation by ATSM (diacetyl-bis(N4-methylthiosemicarbazone)) and a water soluble analogue

The chelator diacetyl-bis(N4-methylthiosemicarbazone) (ATSM) and its complexes with CuII and ZnII are becoming increasingly investigated for medical applications such as PET imaging for anti-tumour therapy and the treatment of amyotrophic lateral sclerosis. However, the solubility in water of both the ligand and the complexes presents certain limitations for in vitro studies. Moreover, the stability of the CuII and ZnII complexes and their metal exchange reaction against the potential biological competitor human serum albumin (HSA) has not been studied in depth. In this work it was observed that the ATSM with an added carboxylic group into the structure increases its solubility in aqueous solutions without altering the coordination mode and the conjugated system of the ligand. The poorly water-soluble CuII- and ZnII-ATSM complexes were prevented from precipitating due to the binding to HSA. Both HSA and ATSM show a similar thermodynamic affinity for ZnII. Finally, the CuII-competition experiments with EDTA and the water-soluble ATSM ligands yielded an apparent log Kd at pH 7.4 of about -19. When ATSM was added to CuII- and ZnII-loaded HSA, withdrawing of ZnII was kinetically favoured, but this metal is slowly substituted by the CuII afterwards taken from HSA so that this protein could be considered as a source of CuII for ATSM.

Advances in PET and MRI imaging of tumor hypoxia

Tumor hypoxia is a complex and evolving phenomenon both in time and space. Molecular imaging allows to approach these variations, but the tracers used have their own limitations. PET imaging has the disadvantage of low resolution and must take into account molecular biodistribution, but has the advantage of high targeting accuracy. The relationship between the signal in MRI imaging and oxygen is complex but hopefully it would lead to the detection of truly oxygen-depleted tissue. Different ways of imaging hypoxia are discussed in this review, with nuclear medicine tracers such as [¹⁸F]-FMISO, [¹⁸F]-FAZA, or [⁶⁴Cu]-ATSM but also with MRI techniques such as perfusion imaging, diffusion MRI or oxygen-enhanced MRI. Hypoxia is a pejorative factor regarding aggressiveness, tumor dissemination and resistance to treatments. Therefore, having accurate tools is particularly important.

Identification of a Novel Cuproptosis-Related Gene Signature for Prognostic Implication in Head and Neck Squamous Carcinomas

Simple Summary

Head and neck squamous carcinoma (HNSC) is a common malignancy that requires novel therapeutic targets. Cuproptosis is an emerging research hotspot. The purpose of this study is to mine the cuproptosis-related genes to find prognosis-related genes. We successfully identified a 24-gene signature for predicting overall survival (OS) in HNSC patients and may expand the range of potential targets for treating HNSC.

Abstract

Head and neck squamous carcinoma (HNSC) is a frequent and deadly malignancy that is challenging to manage. The existing treatment options have considerable efficacy limitations. Hence, the identification of new therapeutic targets and the development of efficacious treatments are urgent needs. Cuproptosis, a non-apoptotic programmed cell death caused by excess copper, has only very recently been discovered. The present study investigated the prognostic importance of genes involved in cuproptosis through the mRNA expression data and related clinical information of HNSC patients downloaded from public databases. Our results revealed that many cuproptosis-related genes were differentially expressed between normal and HNSC tissues in the TCGA cohort. Moreover, 39 differentially expressed genes were associated with the prognosis of HNSC patients. Then, a 24-gene signature was identified in the TCGA cohort utilizing the LASSO Cox regression model. HNSC expression data used for validation were obtained from the GEO database. Consequently, we divided patients into high- and low-risk groups based on the 24-gene signature. Furthermore, we demonstrated that the high-risk group had a worse prognosis when compared to the low-risk group. Additionally, significant differences were found between the two groups in metabolic pathways, immune microenvironment, etc. In conclusion, we found a cuproptosis-related gene signature that can be used effectively to predict OS in HNSC patients. Thus, targeting cuproptosis might be an alternative and promising strategy for HNSC patients.

Radiopharmaceuticals for PET and SPECT Imaging: A Literature Review over the Last Decade

Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of several metabolic processes, blood flow measurements, regional chemical composition, and/or chemical absorption. Depending on the targeted processes within the living organism, different tracers are used for various medical conditions, such as cancer, particular brain pathologies, cardiac events, and bone lesions, where the most commonly used tracers are radiolabeled with 18F (e.g., [¹⁸F]-FDG and NA [¹⁸F]). Oxygen-15 isotope is mostly involved in blood flow measurements, whereas a wide array of ¹¹C-based compounds have also been developed for neuronal disorders according to the affected neuroreceptors, prostate cancer, and lung carcinomas. In contrast, the single-photon emission computed tomography (SPECT) technique uses gamma-emitting radioisotopes and can be used to diagnose strokes, seizures, bone illnesses, and infections by gauging the blood flow and radio distribution within tissues and organs. The radioisotopes typically used in SPECT imaging are iodine-123, technetium-99m, xenon-133, thallium-201, and indium-111. This systematic review article aims to clarify and disseminate the available scientific literature focused on PET/SPECT radiotracers and to provide an overview of the conducted research within the past decade, with an additional focus on the novel radiopharmaceuticals developed for medical imaging.

Modulation of Intracellular Copper Levels as the Mechanism of Action of Anticancer Copper Complexes: Clinical Relevance

Copper (Cu) is a vital element required for cellular growth and development; however, even slight changes in its homeostasis might lead to severe toxicity and deleterious medical conditions. Cancer patients are typically associated with higher Cu content in serum and tumor tissues, indicating increased demand of cancer cells for this micronutrient. Cu is known to readily cycle between the +1 and +2 oxidation state in biological systems. The mechanism of action of Cu complexes is typically based on their redox activity and induction of reactive oxygen species (ROS), leading to deadly oxidative stress. However, there are a number of other biomolecular mechanisms beyond ROS generation that contribute to the activity of anticancer Cu drug candidates. In this review, we discuss how interfering with intracellular Cu balance via either diet modification or addition of inorganic Cu supplements or Cu-modulating compounds affects tumor development, progression, and sensitivity to treatment modalities. We aim to provide the rationale for the use of Cu-depleting and Cu-overloading conditions to generate the best possible patient outcome with minimal toxicity. We also discuss the advantages of the use of pre-formed Cu complexes, such as Cu-(bis)thiosemicarbazones or Cu-N-heterocyclic thiosemicarbazones, in comparison with the in situ formed Cu complexes with metal-binding ligands. In this review, we summarize available clinical and mechanistic data on clinically relevant anticancer drug candidates, including Cu supplements, Cu chelators, Cu ionophores, and Cu complexes.

Recent Advances in Radiometals for Combined Imaging and Therapy in Cancer

Nuclear medicine is defined as the use of radionuclides for diagnostic and therapeutic applications. The imaging modalities positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are based on γ-emissions of specific energies. The therapeutic technologies are based on β^- -particle-, α-particle-, and Auger electron emitters. In oncology, PET and SPECT are used to detect cancer lesions, to determine dosimetry, and to monitor therapy effectiveness. In contrast, radiotherapy is designed to irreparably damage tumor cells in order to eradicate or control the disease's progression. Radiometals are being explored for the development of diagnostic and therapeutic radiopharmaceuticals. Strategies that combine both modalities (diagnostic and therapeutic), referred to as theranostics, are promising candidates for clinical applications. This review provides an overview of the basic concepts behind therapeutic and diagnostic radiopharmaceuticals and their significance in contemporary oncology. Select radiometals that significantly impact current and upcoming cancer treatment strategies are grouped as clinically suitable theranostics pairs. The most important physical and chemical properties are discussed. Standard production methods and current radionuclide availability are provided to indicate whether a cost-efficient use in a clinical routine is feasible. Recent preclinical and clinical developments and outline perspectives for the radiometals are highlighted in each section.

2020 FDA TIDES (Peptides and Oligonucleotides) Harvest

2020 has been an extremely difficult and challenging year as a result of the coronavirus disease 2019 (COVID-19) pandemic and one in which most efforts have been channeled into tackling the global health crisis. The US Food and Drug Administration (FDA) has approved 53 new drug entities, six of which fall in the peptides and oligonucleotides (TIDES) category. The number of authorizations for these kinds of drugs has been similar to that of previous years, thereby reflecting the consolidation of the TIDES market. Here, the TIDES approved in 2020 are analyzed in terms of chemical structure, medical target, mode of action, and adverse effects.

Non-FDG PET/CT

The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.

Hypoxia imaging and theranostic potential of [64Cu][Cu(ATSM)] and ionic Cu(II) salts: a review of current evidence and discussion of the retention mechanisms

Background

Tumor hypoxia (low tissue oxygenation) is an adverse condition of the solid tumor environment, associated with malignant progression, radiotherapy resistance, and poor prognosis. One method to detect tumor hypoxia is by positron emission tomography (PET) with the tracer [⁶⁴Cu][Cu-diacetyl-bis(N(4)-methylthiosemicarbazone)] ([⁶⁴Cu][Cu(ATSM)]), as demonstrated in both preclinical and clinical studies. In addition, emerging studies suggest using [⁶⁴Cu][Cu(ATSM)] for molecular radiotherapy, mainly due to the release of therapeutic Auger electrons from copper-64, making [⁶⁴Cu][Cu(ATSM)] a “theranostic” agent. However, the radiocopper retention based on a metal-ligand dissociation mechanism under hypoxia has long been controversial. Recent studies using ionic Cu(II) salts as tracers have raised further questions on the original mechanism and proposed a potential role of copper itself in the tracer uptake. We have reviewed the evidence of using the copper radiopharmaceuticals [^60/61/62/64Cu][Cu(ATSM)]/ionic copper salts for PET imaging of tumor hypoxia, their possible therapeutic applications, issues related to the metal-ligand dissociation mechanism, and possible explanations of copper trapping based on studies of the copper metabolism under hypoxia.

Results

We found that hypoxia selectivity of [⁶⁴Cu][Cu(ATSM)] has been clearly demonstrated in both preclinical and clinical studies. Preclinical therapeutic studies in mice have also demonstrated promising results, recently reporting significant tumor volume reductions and improved survival in a dose-dependent manner. Cu(II)-[Cu(ATSM)] appears to be accumulated in regions with substantially higher CD133⁺ expression, a marker for cancer stem cells. This, combined with the reported requirement of copper for activation of the hypoxia inducible factor 1 (HIF-1), provides a possible explanation for the therapeutic effects of [⁶⁴Cu][Cu(ATSM)]. Comparisons between [⁶⁴Cu][Cu(ATSM)] and ionic Cu(II) salts have showed similar results in both imaging and therapeutic studies, supporting the argument for the central role of copper itself in the retention mechanism.

Conclusions

We found promising evidence of using copper-64 radiopharmaceuticals for both PET imaging and treatment of hypoxic tumors. The Cu(II)-[Cu(ATSM)] retention mechanism remains controversial and future mechanistic studies should be focused on understanding the role of copper itself in the hypoxic tumor metabolism.

64Cu-based Radiopharmaceuticals in Molecular Imaging

Copper-64 (T_1/2 = 12.7 hours; β⁺: 19%, β^-: 38%) has a unique decay profile and can be used for positron emission tomography imaging and radionuclide therapy. The well-established coordination chemistry of copper allows for its reaction with different types of chelator systems. It can be linked to antibodies, proteins, peptides, and other biologically relevant small molecules. Two potential ways to produce copper-64 radioisotopes concern the use of the cyclotron or the reactor. This review summarized several commonly used biomarkers of copper-64 radionuclide.

Emerging Functional Imaging Biomarkers of Tumour Responses to Radiotherapy

Tumour responses to radiotherapy are currently primarily assessed by changes in size. Imaging permits non-invasive, whole-body assessment of tumour burden and guides treatment options for most tumours. However, in most tumours, changes in size are slow to manifest and can sometimes be difficult to interpret or misleading, potentially leading to prolonged durations of ineffective treatment and delays in changing therapy. Functional imaging techniques that monitor biological processes have the potential to detect tumour responses to treatment earlier and refine treatment options based on tumour biology rather than solely on size and staging. By considering the biological effects of radiotherapy, this review focusses on emerging functional imaging techniques with the potential to augment morphological imaging and serve as biomarkers of early response to radiotherapy.

Hypoxia Mediates Tumor Malignancy and Therapy Resistance

Hypoxia is a hallmark of the tumor microenvironment and contributes to tumor malignant phenotypes. Hypoxia-inducible factor (HIF) is a master regulator of intratumoral hypoxia and controls hypoxia-mediated pathological processes in tumors, including angiogenesis, metabolic reprogramming, epigenetic reprogramming, immune evasion, pH homeostasis, cell migration/invasion, stem cell pluripotency, and therapy resistance. In this book chapter, we reviewed the causes and types of intratumoral hypoxia, hypoxia detection methods, and the oncogenic role of HIF in tumorigenesis and chemo- and radio-therapy resistance.

The Promise of Novel Biomarkers for Head and Neck Cancer from an Imaging Perspective

It is an agreed fact that overall survival among head and neck cancer patients has increased over the last decade. Several factors however, are still held responsible for treatment failure requiring more in-depth evaluation. Among these, hypoxia and proliferation-specific parameters are the main culprits, along with the more recently researched cancer stem cells. This paper aims to present the latest developments in the field of biomarkers for hypoxia, stemness and tumour proliferation, from an imaging perspective that includes both Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) as well as functional magnetic resonance imaging (MRI). Quantitative imaging of biomarkers is a prerequisite for accurate treatment response assessment, bringing us closer to the highly needed personalised therapy.

Establishing Reliable Cu-64 Production Process: From Target Plating to Molecular Specific Tumor Micro-PET Imaging

Copper-64 is a useful radioisotope for positron emission tomography (PET). Due to the wide range of applications, the demand of ⁶⁴Cu with low metallic impurities is increasing. Here we report a simple method for the efficient production of high specific activity ⁶⁴Cu using a cyclotron for biomedical application. We designed new equipment based on the plating of enriched ⁶⁴Ni as the target, and used automated ion exchange chromatography to purify copper-64 efficiently after irradiation and dissolution of the target in good radiochemical and chemical yield and purity. The ⁶⁴Cu radionuclide produced using 99.32% enriched ⁶⁴Ni with a density of 61.4 ± 5.0 mg/cm², reaching a total radioactivity greater than 200 mCi, with specific activity up to 5.6 GBq/μmoL. It was further incorporated into modified monoclonal antibody DOTA-rituximab to synthesize ⁶⁴Cu-DOTA-rituximab, which was used successfully for micro-PET imaging.

Association between hypoxic volume and underlying hypoxia-induced gene expression in oropharyngeal squamous cell carcinoma

BACKGROUND

Hypoxia imaging is a promising tool for targeted therapy but the links between imaging features and underlying molecular characteristics of the tumour have not been investigated. The aim of this study was to compare hypoxia biomarkers and gene expression in oropharyngeal squamous cell carcinoma (OPSCC) diagnostic biopsies with hypoxia imaged with 64Cu-ATSM PET/CT.

METHODS

64Cu-ATSM imaging, molecular and clinical data were obtained for 15 patients. Primary tumour SUVmax, tumour to muscle ratio (TMR) and hypoxic volume were tested for association with reported hypoxia gene signatures in diagnostic biopsies. A putative gene signature for hypoxia in OPSCCs (hypoxic volume-associated gene signature (HVS)) was derived.

RESULTS

Hypoxic volume was significantly associated with a reported hypoxia gene signature (rho=0.57, P=0.045), but SUVmax and TMR were not. Immunohistochemical staining with the hypoxia marker carbonic anhydrase 9 (CA9) was associated with a gene expression hypoxia response (rho=0.63, P=0.01). Sixteen genes were positively and five genes negatively associated with hypoxic volume (adjusted P<0.1; eight genes had adjusted P<0.05; HVS). This signature was associated with inferior 3-year progression-free survival (HR=1.5 (1.0-2.2), P=0.047) in an independent patient cohort.

CONCLUSIONS

64Cu-ATSM-defined hypoxic volume was associated with underlying hypoxia gene expression response. A 21-gene signature derived from hypoxic volume from patients with OPSCCs in our study may be linked to progression-free survival.

Early and delayed evaluation of solid tumours with 64Cu-ATSM PET/CT: a pilot study on semiquantitative and computer-aided fractal geometry analysis

OBJECTIVE

The aim of this study was to analyse early and delayed acquisition on copper-64 diacetyl-bisN4-methylthiosemicarbazone (Cu-ATSM) PET/CT in a small cohort of patients by comparing semiquantitative and computer-aided fractal geometry analyses.

PATIENTS AND METHODS

Five cancer patients, including non-small-cell lung cancer and head and neck cancer, were investigated with Cu-ATSM PET/CT. Participants received an intravenous injection of Cu-ATSM according to body size and were imaged 60 min (early) and 16 h (delayed) later on hybrid PET/CT. Reconstructed images were visualized on advanced workstations for the definition of semiquantitative parameters: standardized uptake value (SUV)max, SUVratio-to-muscle, SUVmean, hypoxic volume (HV) and hypoxic burden (HB=HV×SUVmean). DICOM data retrieved from both scans were analysed using an ad-hoc computer program to determine the mean intensity value, SD, relative dispersion, three-dimensional histogram fractal dimension and three-dimensional fractal dimension.

RESULTS

All tumour lesions showed increased uptake of Cu-ATSM at early evaluation, with a median SUVratio-to-muscle of 4.42 (range: 1.58-5.62), a median SUVmax of 5.3 (range: 1.9-7.3), a median SUVmean of 2.8 (range: 1.5-3.9), a median HV of 41.6 cm (range: 2.8-453.7) and a median HB of 161.5 cm (range: 4.4-1112.5). All semiquantitative data obtained at 1 h were consistent with the parameters obtained on delayed imaging (P>0.05). A borderline statistically significant difference was found only for SUVmax of the muscle (P=0.045). Fractal geometry analysis on DICOM images showed that all parameters at early imaging showed no statistically significant difference with late acquisition (P>0.05).

CONCLUSION

Our findings support the consistency of Cu-ATSM PET/CT images obtained at early and delayed acquisition for the assessment of tumour lesions.

One Coin, No Need to Flip: Shared PET Targets in Cancer and Coronary Artery Disease

OBJECTIVE

The purposes of this article are to review the common biologic features of cancer and coronary artery disease assessed with PET tracers, focusing on those already used in the clinic and those with translational potential, and to discuss the current value and expected contribution of PET in diagnosis, risk stratification, and treatment monitoring.

CONCLUSION

PET using a wide variety of radiotracers enhances understanding of pathophysiologic changes shared by cancer and coronary artery disease, helps establish an accurate diagnosis, and aids in prognostic assessment and management decisions. It is likely that with the evolution of therapeutic strategies for blocking the development and progression of both diseases and with the introduction of novel, specific ligands in clinical practice, PET will play an ever stronger role in diagnosis, risk stratification, and monitoring of therapy.

Cyclam te1pa for64Cu PET imaging. Bioconjugation to antibody, radiolabeling and preclinical application in xenografted colorectal cancer

te1pa conjugated to an F6 antibody was confirmed to be an interesting alternative to dota for⁶⁴Cuin vivoPET imaging.

Non-18F-FDG PET/CT in the management of patients affected by HNC: state-of-the-art

PET/computed tomography with F-fluorodeoxyglucose is considered a powerful molecular imaging technique that can provide useful information in the management of patients affected by head and neck cancer. However, misleading findings have been reported because of nonspecific uptake caused by peritumoural inflammation and physiologic changes in nonmalignant tissues in the head and neck region. More specific β-emitting tracers have been introduced that can track other pathological processes. We aimed to review the existing literature performing the search until June 2015 on non-F-fluorodeoxyglucose PET tracers in head and neck cancer to highlight their role in clinical practice.

Prognostic Evaluation of Disease Outcome in Solid Tumors Investigated With 64Cu-ATSM PET/CT

PURPOSE

Cu-ATSM is a very promising PET radiopharmaceutical for tumor imaging of hypoxia. One of the advantages of this compound compared with other hypoxia-avid tracers is the high tumor-to-background signal offered, which guaranties facilitated tumor delineation. This study analyzes optimal semiquantitative and quantitative parameters obtained by Cu-ATSM PET/CT in the same cohort of patients with special focus on their correlation to disease outcome.

PATIENTS AND METHODS

A prospective recruitment of 18 consecutive patients (M:F, 13:5; mean age, 60.7 years) with locally advanced non-small cell lung cancer (n = 7) or head and neck cancer (HNC) was performed. Each participant received 105 to 500 MBq of tracer according to body size and was scanned in a 3-dimensional mode PET/CT 60 minutes after tracer injection. PET images were reconstructed and visualized on a GE Advanced 4.6 workstation for the definition of semiquantitative and quantitative parameters: SUVmax, SUVratio-to-muscle, hypoxic tumor volume (HTV), and hypoxic burden (HB = HTV × SUVmean). These data were subsequently correlated to disease outcome, expressed in terms of progression-free survival calculated on a follow-up period with a median of 14.6 months.

RESULTS

All patients showed a moderately to highly increased uptake of Cu-ATSM in tumor lesions, with a mean SUVmax of 5.2 (range, 1.9-8.3) and mean SUVratio of 4.4 (range, 1.6-6.8). In addition, a broad range of HTV and HB was defined as mean values of 99.3 cm (range, 2.5-453.7 cm) and 301 (4.2-1134), respectively. Receiver operating characteristic analysis identified as reference cutoffs with respect to disease outcome with the following values: SUVmax >2.5 (AUC, 0.57; sensitivity, 88.9%; specificity, 50%), SUVratio ≤4.4 (AUC, 0.60; sensitivity, 50; specificity, 83.3%), HTV >160.7 cm (AUC, 0.61; sensitivity, 55.6%; specificity, 75%), and HB >160.7 (AUC, 0.67; sensitivity, 58.3%; specificity, 83.3%). In our cohort, HB showed a statistically significant difference in terms of mean values on the analysis of variance test with respect to disease progression (P = 0.04). On univariate analysis, Cox regression confirmed these findings and showed a significant correlation to progression-free survival for HB (P = 0.05) and HTV (P = 0.02).

CONCLUSIONS

In our cohort, the definition of optimal semiquantitative and quantitative parameters on Cu-ATSM PET/CT seems feasible and in line with previously published data. However, when considering the prognostic role with respect to disease outcome, the more robust parameters are represented by HTV and HB.

Micro Regional Heterogeneity of 64Cu-ATSM and 18F-FDG Uptake in Canine Soft Tissue Sarcomas: Relation to Cell Proliferation, Hypoxia and Glycolysis

OBJECTIVES

Tumour microenvironment heterogeneity is believed to play a key role in cancer progression and therapy resistance. However, little is known about micro regional distribution of hypoxia, glycolysis and proliferation in spontaneous solid tumours. The overall aim was simultaneous investigation of micro regional heterogeneity of 64Cu-ATSM (hypoxia) and 18F-FDG (glycolysis) uptake and correlation to endogenous markers of hypoxia, glycolysis, proliferation and angiogenesis to better therapeutically target aggressive tumour regions and prognosticate outcome.

METHODS

Exploiting the different half-lives of 64Cu-ATSM (13 h) and 18F-FDG (2 h) enabled simultaneous investigation of micro regional distribution of hypoxia and glycolysis in 145 tumour pieces from four spontaneous canine soft tissue sarcomas. Pairwise measurements of radioactivity and gene expression of endogenous markers of hypoxia (HIF-1α, CAIX), glycolysis (HK2, GLUT1 and GLUT3), proliferation (Ki-67) and angiogenesis (VEGFA and TF) were performed. Dual tracer autoradiography was compared with Ki-67 immunohistochemistry.

RESULTS

Micro regional heterogeneity in hypoxia and glycolysis within and between tumour sections of each tumour piece was observed. The spatial distribution of 64Cu-ATSM and 18F-FDG was rather similar within each tumour section as reflected in moderate positive significant correlations between the two tracers (ρ = 0.3920-0.7807; p = 0.0180 -<0.0001) based on pixel-to-pixel comparisons of autoradiographies and gamma counting of tumour pieces. 64Cu-ATSM and 18F-FDG correlated positively with gene expression of GLUT1 and GLUT3, but negatively with HIF-1α and CAIX. Significant positive correlations were seen between Ki-67 gene expression and 64Cu-ATSM (ρ = 0.5578, p = 0.0004) and 18F-FDG (ρ = 0.4629-0.7001, p = 0.0001-0.0151). Ki-67 gene expression more consistently correlated with 18F-FDG than with 64Cu-ATSM.

CONCLUSIONS

Micro regional heterogeneity of hypoxia and glycolysis was documented in spontaneous canine soft tissue sarcomas. 64Cu-ATSM and 18F-FDG uptakes and distributions showed significant moderate correlations at the micro regional level indicating overlapping, yet different information from the tracers.18F-FDG better reflected cell proliferation as measured by Ki-67 gene expression than 64Cu-ATSM.

Radiopharmaceuticals as probes to characterize tumour tissue

Tumour cells exhibit several properties that allow them to grow and divide. A number of these properties are detectable by nuclear imaging methods. We discuss crucial tumour properties that can be described by current radioprobe technologies, further discuss areas of emerging radioprobe development, and finally articulate need areas that our field should aspire to develop. The review focuses largely on positron emission tomography and draws upon the seminal 'Hallmarks of Cancer' review article by Hanahan and Weinberg in 2011 placing into context the present and future roles of radiotracer imaging in characterizing tumours.

Assessing tumor hypoxia in head and neck cancer by PET with ⁶²Cu-diacetyl-bis(N⁴-methylthiosemicarbazone)

PURPOSE

The aim of this study was to investigate the potential of PET imaging with a hypoxia-selective tracer ⁶²Cu-diacetyl-bis(N⁴-methylthiosemicarbazone) (⁶²Cu-ATSM) for evaluating the prognosis of patients with head and neck cancer (HNC).

METHODS

Twenty-five patients with HNC including stage II to IV underwent both ⁶²Cu-ATSM and ¹⁸F-FDG PET before the initiation of treatment. Volumes of interest were placed on the tumor and sternocleidomastoid muscles to obtain SUVmax and to calculate the tumor-to-muscle activity ratio (TMR). The PET results were correlated with clinical follow-up, and the receiver operating characteristic analysis was used to determine the optimal cutoff values. Progression-free survival (PFS) and cause-specific survival (CSS) were statistically analyzed.

RESULTS

Patients were followed up for periods ranging from 4 to 32 months. Twelve patients died from local recurrence or metastasis of a primary cancer, and 2 had recurrence of the 13 remaining patients. Mean (SD) periods of PFS and CSS were 15.5 (12.5) and 18.6 (11.0) months, respectively. Optimal cutoff values for each PET index were as follows: SUVs of ⁶²Cu-ATSM (SUVATSM) and FDG were 3.6 and 7.9; TMRs of ATSM (TMRATSM) and FDG were 3.2 and 5.6. When the cutoff for TMRATSM was set at 3.2, patients with a greater TMRATSM had significantly worse PFS (P = 0.014) and CSS (P = 0.031). Two-year PFS and CSS rates were 73% and 80% for patients with a lower TMRATSM (≤3.2); however, they were 20% and 33% for those with hypoxic tumors (TMRATSM, >3.2), respectively. F-FDG-related indices did not show any significant difference in either PFS or CSS.

CONCLUSIONS

Pretreatment ⁶²Cu-ATSM PET is useful for predicting the prognosis of patients with HNC.

Hypoxia in head and neck cancer in theory and practice: a PET-based imaging approach

Hypoxia plays an important role in tumour recurrence among head and neck cancer patients. The identification and quantification of hypoxic regions are therefore an essential aspect of disease management. Several predictive assays for tumour oxygenation status have been developed in the past with varying degrees of success. To date, functional imaging techniques employing positron emission tomography (PET) have been shown to be an important tool for both pretreatment assessment and tumour response evaluation during therapy. Hypoxia-specific PET markers have been implemented in several clinics to quantify hypoxic tumour subvolumes for dose painting and personalized treatment planning and delivery. Several new radiotracers are under investigation. PET-derived functional parameters and tracer pharmacokinetics serve as valuable input data for computational models aiming at simulating or interpreting PET acquired data, for the purposes of input into treatment planning or radio/chemotherapy response prediction programs. The present paper aims to cover the current status of hypoxia imaging in head and neck cancer together with the justification for the need and the role of computer models based on PET parameters in understanding patient-specific tumour behaviour.

PET/CT in therapy evaluation of patients with lung cancer

FDG-PET/CT is a well documented and widespread used imaging modality for the diagnosis and staging of patient with lung cancer. FDG-PET/CT is increasingly used for the assessment of treatment effects during and after chemotherapy. However, PET is not an accepted surrogate end-point for assessment of response rate in clinical trials. The aim of this review is to present current evidence on the use of PET in response evaluation of patients with lung cancer and to introduce the pearls and pitfalls of the PET-technology relating to response assessment. Based on this and relating to validation criteria, including stable technology, standardization, reproducibility and broad availability, the review discusses why, despite numerous studies on response assessment indicating a possible role for FDG-PET/CT, PET still has no place in guidelines relating to response evaluation in lung cancer.