Personalized versus evidence-based medicine with PET-based imaging

Cold Kit Labeling: The Future of 68Ga Radiopharmaceuticals?

Over the last couple of decades, gallium-68 (68Ga) has gained a formidable interest for PET molecular imaging of various conditions, from cancer to infection, through cardiac pathologies or neuropathies. It has gained routine use, with successful radiopharmaceuticals such as somatostatin analogs ([68Ga]Ga-DOTATOC and [68Ga]GaDOTATATE) for neuroendocrine tumors, and PSMA ligands for prostate cancer. It represents a major clinical impact, particularly in the context of theranostics, coupled with their 177Lu-labeled counterparts. Beside those, a bunch of new 68Ga-labeled molecules are in the preclinical and clinical pipelines, with some of them showing great promise for patient care. Increasing clinical demand and regulatory issues have led to the development of automated procedures for the production of 68Ga radiopharmaceuticals. However, the widespread use of these radiopharmaceuticals may rely on simple and efficient radiolabeling methods, undemanding in terms of equipment and infrastructure. To make them technically and economically accessible to the medical community and its patients, it appears mandatory to develop a procedure similar to the well-established kit-based 99mTc chemistry. Already available commercial kits for the production of 68Ga radiopharmaceuticals have demonstrated the feasibility of using such an approach, thus paving the way for more kit-based 68Ga radiopharmaceuticals to be developed. This article discusses the development of 68Ga cold kit radiopharmacy, including technical issues, and regulatory aspects.

Role of 18F-fluorodeoxyglucose (FDG) and 18F-2-fluorodeoxy sorbitol (FDS) in autoimmune hypophysitis: a case report

BACKGROUND

Autoimmune hypophysitis is a rare disease characterized by the infiltration of lymphocytic cells into the pituitary gland. ¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-2-fluorodeoxy sorbitol (FDS) positron emission tomography (PET) are well-established and emerging techniques, respectively, which may aid in the diagnosis and classification of autoimmune hypophysitis.

CASE PRESENTATION

Here, we report a 40-year-old female diagnosed with central diabetes insipidus and multiple pituitary hormone deficiencies, and MRI revealed homogeneous signals in the pituitary gland as well as thickened in the pituitary stalk. FDG PET localized the pituitary and pituitary stalk lesions and displayed an SUVmax of 5.5. FDS, a sensitive radiotracer for bacterial infections but remains unproven under aseptic inflammation, also demonstrated elevated radioactivity, with an SUVmax of 1.1 at 30 min and 0.73 at 120 min. Transnasal biopsy suggested a diagnosis of autoimmune hypophysitis, and the patient displayed radiological and clinical improvement after treatment with glucocorticoids and hormone replacement.

CONCLUSIONS

Autoimmune hypophysitis can display elevated FDG uptake, which aids in the localization of the lesions. In addition to revealing bacterial infection specifically, FDS can also accumulate under autoimmune conditions, suggesting that it could serve as a potential radiotracer for both bacterial and aseptic inflammation.

TRIAL REGISTRATION

The patient was enrolled in study NCT02450942 (clinicaltrials.gov, Registered May 21, 2015).

Metabolic reprogramming of host cells upon bacterial infection: Why shift to a Warburg-like metabolism?

The finding that the Warburg effect observed in proliferating cancer cells is also observed during immune responses renewed the interest in the study of metabolic reprogramming of immune cells, a field of investigation called immunometabolism. However, the specific mechanisms and processes underlying metabolic changes of host cells upon bacterial infection remain poorly understood. Several recent reports have reported that mammalian cells infected with intracellular bacteria have an altered metabolism that resembles the Warburg effect seen in cancer cells. In this Review, we will summarize current knowledge on metabolic reprogramming and discuss putative causes underlying the preferential remodelling of host cells to Warburg-like metabolic programs during infection by intracellular bacteria.

PET-Based Personalized Management in Clinical Oncology: An Unavoidable Path for the Foreseeable Future

It is imperative that the thrust of clinical practice in the ensuing years would be to develop personalized management model for various disorders. PET-computed tomography (PET-CT) based molecular functional imaging has been increasingly utilized for assessment of tumor and other nonmalignant disorders and has the ability to explore disease phenotype on an individual basis and address critical clinical decision making questions related to practice of personalized medicine. Hence, it is essential to make a concerted systematic effort to explore and define the appropriate place of PET-CT in personalized clinical practice in each of malignancies, which would strengthen the concept further. The potential advantages of PET based disease management can be classified into broad categories: (1) Traditional: which includes assessment of disease extent such as initial disease staging and restaging, treatment response evaluation particularly early in the course and thus PET-CT response adaptive decision for continuing the same regimen or switching to salvage schedules; there has been continuous addition of newer application of PET based disease restaging in oncological parlance (eg, Richter transformation); (2) Recent and emerging developments: this includes exploring tumor biology with FDG and non-FDG PET tracers. The potential of multitracer PET imaging (particularly new and novel tracers, eg, 68Ga-DOTA-TOC/NOC/TATE in NET, 68Ga-PSMA and 18F-fluorocholine in prostate carcinoma, 18F-fluoroestradiol in breast carcinoma) has provided a scientific basis to stratify and select appropriate targeted therapies (both radionuclide and nonradionuclide treatment), a major boost for individualized disease management in clinical oncology. Integrating the molecular level information obtained from PET with structural imaging further individualizing treatment plan in radiation oncology, precision of interventions and biopsies of a particular lesion and forecasting disease prognosis.

Emerging clinical applications of PET based molecular imaging in oncology: the promising future potential for evolving personalized cancer care

This review focuses on the potential of advanced applications of functional molecular imaging in assessing tumor biology and cellular characteristics with emphasis on positron emission tomography (PET) applications with both 18-fluorodeoxyglucose (FDG) and non-FDG tracers. The inherent heterogeneity of cancer cells with their varied cellular biology and metabolic and receptor phenotypic expression in each individual patient and also intra-and inter-lesionally in the same individual mandates for transitioning from a generalized “same-size-fits-all” approach to personalized medicine in oncology. The past two decades have witnessed improvement of oncological imaging through CT, MR imaging, PET, subsequent movement through hybrid or fusion imaging with PET/CT and single-photon emission computerized tomography (SPECT-CT), and now toward the evolving PET/MR imaging. These recent developments have proven invaluable in enhancing oncology care and have the potential to help image the tumor biology at the cellular level, followed by providing a tailored treatment. Molecular imaging, integrated diagnostics or Radiomics, biology-driven interventional radiology and theranostics, all hold immense potential to serve as a guide to give “start and stop” treatment for a patient on an individual basis. This will likely have substantial impact on both treatment costs and outcomes. In this review, we bring forth the current trends in molecular imaging with established techniques (PET/CT), with particular emphasis on newer molecules (such as amino acid metabolism and hypoxia imaging, somatostatin receptor based imaging, and hormone receptor imaging) and further potential for FDG. An introductory discussion on the novel hybrid imaging techniques such as PET/MR is also made to understand the futuristic trends.

(99m)Tc-Annexin A5 quantification of apoptotic tumor response: a systematic review and meta-analysis of clinical imaging trials

PURPOSE

(99m)Tc-Annexin A5 has been used as a molecular imaging probe for the visualization, characterization and measurement of apoptosis. In an effort to define the quantitative (99m)Tc-annexin A5 uptake criteria that best predict tumor response to treatment, we performed a systematic review and meta-analysis of the results of all clinical imaging trials found in the literature or publicly available databases.

METHODS

Included in this review were 17 clinical trials investigating quantitative (99m)Tc-annexin A5 (qAnx5) imaging using different parameters in cancer patients before and after the first course of chemotherapy and/or radiation therapy. Qualitative assessment of the clinical studies for diagnostic accuracy was performed using the QUADAS-2 criteria. Of these studies, five prospective single-center clinical trials (92 patients in total) were included in the meta-analysis after exclusion of one multicenter clinical trial due to heterogeneity. Pooled positive predictive values (PPV) and pooled negative predictive values (NPV) (with 95% CI) were calculated using Meta-Disc software version 1.4.

RESULTS

Absolute quantification and/or relative quantification of (99m)Tc-annexin A5 uptake were performed at baseline and after the start of treatment. Various quantitative parameters have been used for the calculation of (99m)Tc-annexin A5 tumor uptake and delta (Δ) tumor changes post-treatment compared to baseline including: tumor-to-background ratio (TBR), ΔTBR, tumor-to-noise ratio, relative tumor ratio (TR), ΔTR, standardized tumor uptake ratio (STU), ΔSTU, maximum count per pixel within the tumor volume (Cmax), Cmax%, absolute ΔU and percentage (ΔU%), maximum ΔU counts, semiquantitative visual scoring, percent injected dose (%ID) and %ID/cm(3). Clinical trials investigating qAnx5 imaging have included patients with lung cancer, lymphoma, breast cancer, head and neck cancer and other less common tumor types. In two phase I/II single-center clinical trials, an increase of ≥25% in uptake following treatment was considered a significant threshold for an apoptotic tumor response (partial response, complete response). In three other phase I/II clinical trials, increases of ≥28%, ≥42% and ≥47% in uptake following treatment were found to be the mean cut-off levels in responders. In a phase II/III multicenter clinical trial, an increase of ≥23% in uptake following treatment was found to be the minimum cut-off level for a tumor response. In one clinical trial, no significant difference in (99m)Tc-annexin A5 uptake in terms of %ID was found in healthy tissues after chemotherapy compared to baseline. In two other clinical trials, intraobserver and interobserver measurements of (99m)Tc-annexin A5 tumor uptake were found to be reproducible (mean difference <5%, kappa =  0.90 and 0.82, respectively) and to be highly correlated with treatment outcome (Spearman r = 0.99, p < 0.0001). The meta-analysis demonstrated a pooled positive PPV of 100% (95% CI 92 - 100%) and a pooled NPV of 70% (95% CI 55 - 82%) for prediction of a tumor response after the first course of chemotherapy and/or radiotherapy in terms of ΔU%. In a symmetric sROC analysis, the AUC was 0.919 and the Q* index was 85.21 %.

CONCLUSION

Quantitative (99m)Tc-annexin A5 imaging has been investigated in clinical trials for the assessment of apoptotic tumor responses. This meta-analysis showed a high pooled PPV and a moderate pooled NPV with ΔU cut-off values ranging between 20% and 30%. Standardization of quantification and harmonization of results are required for high-quality clinical research. A standardized uptake value score (SUV, ΔSUV) using quantitative SPECT/CT imaging may be a promising approach to the simple, reproducible and semiquantitative assessment of apoptotic tumor changes.

Specific and sensitive tumor imaging using biostable oligonucleotide aptamer probes

Although several imaging modalities are widely used for tumor imaging, none are tumor type-specific. Different types of cancer exhibit differential therapeutic responses, thus necessitating development of an imaging modality able to detect various tumor types with high specificity. To illustrate this point, CD30-specific oligonucleotide aptamer in vivo imaging probes were conjugated to the near-infrared IRD800CW reporter. Mice bearing xenografted CD30-positive or control CD30-negative lymphoma tumors on contralateral sides of the same mouse were developed. Following a systemic administration of aptamer probes, whole body imaging of tumor-bearing mice was performed. Imaging signal from tumor sites was analyzed and imaging specificity confirmed by tissue immunostaining. The in vivo biodistribution of aptamer probes was also evaluated. Whole body scans revealed that the RNA-based aptamer probes selectively highlighted CD30-expressing lymphoma tumors immediately after systemic administration, but did not react with control tumors in the same mouse. The resultant imaging signal lasted up to 1 hr and the aptamer probes were rapidly eliminated from the body through urinary and lower intestinal tracts. For more sensitive imaging, biostable CD30-specific ssDNA-based aptamer probes were also generated. Systemic administration of these probes also selectively highlighted the CD30-positive lymphoma tumors, with imaging signal detected 4-5 folds higher than that derived from control tumors in the same animal, and lasted for up to 24hr. This study demonstrates that oligonucleotide aptamer probes can provide tumor type-specific imaging with high sensitivity and a long-lasting signal, indicating their potential for clinical applications.

Positron emission tomography image-guided drug delivery: current status and future perspectives

Positron emission tomography (PET) is an important modality in the field of molecular imaging, which is gradually impacting patient care by providing safe, fast, and reliable techniques that help to alter the course of patient care by revealing invasive, de facto procedures to be unnecessary or rendering them obsolete. Also, PET provides a key connection between the molecular mechanisms involved in the pathophysiology of disease and the according targeted therapies. Recently, PET imaging is also gaining ground in the field of drug delivery. Current drug delivery research is focused on developing novel drug delivery systems with emphasis on precise targeting, accurate dose delivery, and minimal toxicity in order to achieve maximum therapeutic efficacy. At the intersection between PET imaging and controlled drug delivery, interest has grown in combining both these paradigms into clinically effective formulations. PET image-guided drug delivery has great potential to revolutionize patient care by in vivo assessment of drug biodistribution and accumulation at the target site and real-time monitoring of the therapeutic outcome. The expected end point of this approach is to provide fundamental support for the optimization of innovative diagnostic and therapeutic strategies that could contribute to emerging concepts in the field of “personalized medicine”. This review focuses on the recent developments in PET image-guided drug delivery and discusses intriguing opportunities for future development. The preclinical data reported to date are quite promising, and it is evident that such strategies in cancer management hold promise for clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in enhanced quality of life for cancer patients.

Bioavailable copper modulates oxidative phosphorylation and growth of tumors

Copper is an essential trace element, the imbalances of which are associated with various pathological conditions, including cancer, albeit via largely undefined molecular and cellular mechanisms. Here we provide evidence that levels of bioavailable copper modulate tumor growth. Chronic exposure to elevated levels of copper in drinking water, corresponding to the maximum allowed in public water supplies, stimulated proliferation of cancer cells and de novo pancreatic tumor growth in mice. Conversely, reducing systemic copper levels with a chelating drug, clinically used to treat copper disorders, impaired both. Under such copper limitation, tumors displayed decreased activity of the copper-binding mitochondrial enzyme cytochrome c oxidase and reduced ATP levels, despite enhanced glycolysis, which was not accompanied by increased invasiveness of tumors. The antiproliferative effect of copper chelation was enhanced when combined with inhibitors of glycolysis. Interestingly, larger tumors contained less copper than smaller tumors and exhibited comparatively lower activity of cytochrome c oxidase and increased glucose uptake. These results establish copper as a tumor promoter and reveal that varying levels of copper serves to regulate oxidative phosphorylation in rapidly proliferating cancer cells inside solid tumors. Thus, activation of glycolysis in tumors may in part reflect insufficient copper bioavailability in the tumor microenvironment.

Assessment of the biodistribution of an [(18) F]FDG-loaded perfluorocarbon double emulsion using dynamic micro-PET in rats

Perfluorocarbon (PFC) double emulsions loaded with a water-soluble, therapeutic agent can be triggered by ultrasound in a process known as acoustic droplet vaporization. Elucidating the stability and biodistribution of these sonosensitive vehicles and encapsulated agents is critical in developing targeted drug delivery strategies using ultrasound. [(18) F]fluorodeoxyglucose (FDG) was encapsulated in a PFC double emulsion and the in vitro diffusion of FDG was assessed using a Franz diffusion cell. Using dynamic micro-positron emission tomography and direct tissue sampling, the biodistribution of FDG administered as a solution (i.e. non-emulsified) or as an emulsion was studied in Fisher 344 rats (n = 6) bearing subcutaneous 9L gliosarcoma. Standardized uptake values (SUVs) and area under the curve of the SUV (AUCSUV ) of FDG were calculated for various tissues. The FDG flux from the emulsion decreased by up to a factor of 6.9 compared with the FDG solution. FDG uptake, calculated from the AUCSUV , decreased by 36% and 44% for brain and tumor, respectively, when comparing FDG solution vs FDG emulsion (p < 0.01). Decreases in AUCSUV in highly metabolic tissues such as brain and tumor demonstrated retention of FDG within the double emulsion. No statistically significant differences in lung AUCSUV were observed, suggesting minimal accumulation of the emulsion in the pulmonary capillary bed. The liver AUCSUV increased by 356% for the FDG emulsion, thus indicating significant hepatic retention of the emulsion.

Personalized oncology: recent advances and future challenges

Personalized oncology is evidence-based, individualized medicine that delivers the right care to the right cancer patient at the right time and results in measurable improvements in outcomes and a reduction on health care costs. Evolving topics in personalized oncology such as genomic analysis, targeted drugs, cancer therapeutics and molecular diagnostics will be discussed in this review. Biomarkers and molecular individualized medicine are replacing the traditional "one size fits all" medicine. In the next decade the treatment of cancer will move from a reactive to a proactive discipline. The essence of personalized oncology lies in the use of biomarkers. These biomarkers can be from tissue, serum, urine or imaging and must be validated. Personalized oncology based on biomarkers is already having a remarkable impact. Three different types of biomarkers are of particular importance: predictive, prognostic and early response biomarkers. Tools for implementing preemptive medicine based on genetic and molecular diagnostic and interventions will improve cancer prevention. Imaging technologies such as Computed Tomography (CT) and Positron Emitted Tomography (PET) are already influencing the early detection and management of the cancer patient. Future advances in imaging are expected to be in the field of molecular imaging, integrated diagnostics, biology driven interventional radiology and theranostics. Molecular diagnostics identify individual cancer patients who are more likely to respond positively to targeted chemotherapies. Molecular diagnostics include testing for genes, gene expression, proteins and metabolites. The use of companion molecular diagnostics is expected to grow significantly in the future and will be integrated into new cancer therapies a single (bundled) package which will provide greater efficiency, value and cost savings. This approach represents a unique opportunity for integration, increased value in personalized oncology.

Personalized medicine: a competitor or an upgrade of evidence-based medicine?

Evidence-based medicine is a method of healthcare decision-making that intends to combine the most reliable scientific information with individual expertise and patient preferences in order to offer the optimal diagnostic and therapeutic option for the patient. In recent years, the term personalized medicine has been introduced to represent an approach considering differences among individual patients. In modern medicine the most important sources of evidence are clinical trials using epidemiological methods, and molecular biological and genetic methods characterizing individual patients. Responses to a certain therapeutic intervention differ among patients for several reasons. Identifying benefits and harms of an intervention can be handled by two approaches. The first is a statistical approach using the rule of large numbers, resulting in statistically meaningful conclusions. The other approach is personalized: the conclusions are valid for individual patients or subgroups identified by well-defined markers. Whether the evidence is statistical deriving from a large number of clinical observations or personalized based on molecular studies - it should be scientifically sound to apply in clinical practice. Confronting evidence-based medicine with personalized medicine would be justified only if the former is misinterpreted and restricted only to the use of randomized trials and their systematic reviews. The practice of personalized medicine is also based on evidence, and in many instances evidence from molecular research is also statistical in nature. Regarding healthcare decision about an individual patient, whether using evidence from randomized trials or from molecular studies of biomarkers, we have to base our decisions on reliable, good quality evidence. Evidence from molecular and genetic medicine thus improves the armament of evidence-based medicine, and this upgrade yields a more reliable support for our decisions in everyday practice.

The development of peptide-based tools for the analysis of angiogenesis

Limitations to the application of molecularly targeted cancer therapies are the inability to accurately match patient with effective treatment and the absence of a prompt readout of posttreatment response. Noninvasive agents that rapidly report vascular endothelial growth factor (VEGF) levels using positron emission tomography (PET) have the potential to enhance anti-angiogenesis therapies. Using phage display, two distinct classes of peptides were identified that bind to VEGF with nanomolar affinity and high selectivity. Co-crystal structures of these different peptide classes demonstrate that both bind to the receptor-binding region of VEGF. (18)F-radiolabelling of these peptides facilitated the acquisition of PET images of tumor VEGF levels in a HM7 xenograph model. The images obtained from one 59-residue probe, (18)F-Z-3B, 2 hr postinjection are comparable to those obtained with anti-VEGF antibody B20 72 hr postinjection. Furthermore, VEGF levels in growing SKOV3 tumors were followed using (18)F-Z-3B as a PET probe with VEGF levels increasing with tumor size.

Medical imaging in personalised medicine: a white paper of the research committee of the European Society of Radiology (ESR)

The future of medicine lies in early diagnosis and individually tailored treatments, a concept that has been designated ‘personalised medicine’ (PM), i.e. delivering the right treatment to the right patient at the right time. However, the value of medical imaging in PM is frequently underestimated, as many policy makers forget the all-important right location in the PM paradigm. Medical imaging has always been personalised as it provides individual assessment of the location and extent of an abnormality, and in the future it will prove fundamental to almost all aspects of PM. Stratification based on imaging biomarkers can help identify individuals suited for preventive intervention and can improve disease staging. In vivo visualisation of locoregional physiological, biochemical and biological processes using molecular imaging can detect diseases in pre-symptomatic phases or facilitate individualised drug delivery. Furthermore, imaging is essential to patient-tailored therapy planning, therapy monitoring and follow-up of disease progression, as well as targeting non-invasive or minimally invasive treatments, especially with the rise of theranostics. For PM to reach its full potential, medical imaging must be an integral part. Radiologists need to be prepared for this new paradigm as it will mean changes in training, in research and in clinical practice.

Transbilayer phospholipids molecular imaging

Nuclear medicine has become a key part of molecular imaging. In the present review article, we focus on the transbilayer phospholipids as exquisite targets for radiolabelled probes in molecular imaging. Asymmetry of phospholipid distribution is a characteristic of mammalian cell membranes. Phosphatidylcholine and sphyngomyelin cholinophospholipids are primarily located within the external leaflet of the cell membrane. Phosphatidylserine and phosphatidylethanolamine aminophospholipids, and also phosphatidylinositol are primarily located within the internal leaflet of the cell membrane. New radiolabelled tracers have been designed in preclinical and clinical research for PET-CT and SPECT-CT molecular imaging of transbilayer phospholipids.