Advances in Radioligand Theranostics in Oncology

Theranostics with radioligands (radiotheranostics) has played a pivotal role in oncology. Radiotheranostics explores the molecular targets expressed on tumor cells to target them for imaging and therapy. In this way, radiotheranostics entails non-invasive demonstration of the in vivo expression of a molecular target of interest through imaging followed by the administration of therapeutic radioligand targeting the tumor-expressed molecular target. Therefore, radiotheranostics ensures that only patients with a high likelihood of response are treated with a particular radiotheranostic agent, ensuring the delivery of personalized care to cancer patients. Within the last decades, a couple of radiotheranostics agents, including Lutetium-177 DOTATATE (177Lu-DOTATATE) and Lutetium-177 prostate-specific membrane antigen (177Lu-PSMA), were shown to prolong the survival of cancer patients compared to the current standard of care leading to the regulatory approval of these agents for routine use in oncology care. This recent string of successful approvals has broadened the interest in the development of different radiotheranostic agents and their investigation for clinical translation. In this work, we present an updated appraisal of the literature, reviewing the recent advances in the use of established radiotheranostic agents such as radioiodine for differentiated thyroid carcinoma and Iodine-131-labeled meta-iodobenzylguanidine therapy of tumors of the sympathoadrenal axis as well as the recently approved 177Lu-DOTATATE and 177Lu-PSMA for differentiated neuroendocrine tumors and advanced prostate cancer, respectively. We also discuss the radiotheranostic agents that have been comprehensively characterized in preclinical studies and have shown some clinical evidence supporting their safety and efficacy, especially those targeting fibroblast activation protein (FAP) and chemokine receptor 4 (CXCR4) and those still being investigated in preclinical studies such as those targeting poly (ADP-ribose) polymerase (PARP) and epidermal growth factor receptor 2.

Prostate-specific Membrane Antigen: Alpha-labeled Radiopharmaceuticals

Novel prostate-specific membrane antigen (PSMA) ligands labeled with α-emitting radionuclides are sparking a growing interest in prostate cancer treatment. These targeted alpha therapies (TATs) have attractive physical properties that deem them effective in progressive metastatic castrate-resistant prostate cancer (mCRPC). Among the PSMA TAT radiopharmaceuticals, [225Ac]Ac-PSMA has been used extensively on a compassionate basis and is currently undergoing phase I trials. Notably, TAT has the potential to improve quality of life and has favorable antitumor activity and outcomes in multiple scenarios other than in mCRPC. In addition, resistance mechanisms to TAT may be amenable to combination therapies.

Insights into Peptidoglycan-Targeting Radiotracers for Imaging Bacterial Infections: Updates, Challenges, and Future Perspectives

The unique structural architecture of the peptidoglycan allows for the stratification of bacteria as either Gram-negative or Gram-positive, which makes bacterial cells distinguishable from mammalian cells. This classification has received attention as a potential target for diagnostic and therapeutic purposes. Bacteria's ability to metabolically integrate peptidoglycan precursors during cell wall biosynthesis and recycling offers an opportunity to target and image pathogens in their biological state. This Review explores the peptidoglycan biosynthesis for bacteria-specific targeting for infection imaging. Current and potential radiolabeled peptidoglycan precursors for bacterial infection imaging, their development status, and their performance in vitro and/or in vivo are highlighted. We conclude by providing our thoughts on how to shape this area of research for future clinical translation.

Actinium-225-PSMA radioligand therapy of metastatic castration-resistant prostate cancer (WARMTH Act): a multicentre, retrospective study

BACKGROUND

Actinium-225 (225Ac) prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) is a novel therapy for metastatic castration-resistant prostate cancer (mCRPC). We aimed to report the safety and antitumour activity of 225Ac-PSMA RLT of mCRPC in a large cohort of patients treated at multiple centres across the world.

METHODS

This retrospective study included patients treated at seven centres in Australia, India, Germany, and South Africa. We pooled data of consecutive patients of any age and Eastern Cooperative Oncology Group performance status with histopathologically confirmed adenocarcinoma of the prostate who were treated with one or more cycles of 8 MBq 225Ac-PSMA RLT administered intravenously for mCRPC. Previous lines of mCRPC treatment included taxane-based chemotherapy, androgen-receptor-axis inhibitors, lutetium-177 (177Lu) PSMA RLT, and radium-223 dichloride. The primary outcomes were overall survival and progression-free survival.

FINDINGS

Between Jan 1, 2016, and May 31, 2023, 488 men with mCRPC received 1174 cycles of 225Ac-PSMA RLT (median two cycles, IQR 2-4). The mean age of the patients was 68·1 years (SD 8·8), and the median baseline prostate-specific antigen was 169·5 ng/mL (IQR 34·6-519·8). Previous lines of treatment were docetaxel in 324 (66%) patients, cabazitaxel in 103 (21%) patients, abiraterone in 191 (39%) patients, enzalutamide in 188 (39%) patients, 177Lu-PSMA RLT in 154 (32%) patients, and radium-223 dichloride in 18 (4%) patients. The median follow-up duration was 9·0 months (IQR 5·0-17·5). The median overall survival was 15·5 months (95% CI 13·4-18·3) and median progression-free survival was 7·9 months (6·8-8·9). In 347 (71%) of 488 patients, information regarding treatment-induced xerostomia was available, and 236 (68%) of the 347 patients reported xerostomia after the first cycle of 225Ac-PSMA RLT. All patients who received more than seven cycles of 225Ac-PSMA RLT reported xerostomia. Grade 3 or higher anaemia occurred in 64 (13%) of 488 patients, leukopenia in 19 (4%), thrombocytopenia in 32 (7%), and renal toxicity in 22 (5%). No serious adverse events or treatment-related deaths were recorded.

INTERPRETATION

225Ac-PSMA RLT shows a substantial antitumour effect in mCRPC and represents a viable therapy option in patients treated with previous lines of approved agents. Xerostomia is a common side-effect. Severe bone marrow and renal toxicity are less common adverse events.

FUNDING

None.

Imaging Molecular Targets and Metabolic Pathways in Breast Cancer for Improved Clinical Management: Current Practice and Future Perspectives

Breast cancer is the most frequently diagnosed cancer and leading cause of cancer-related deaths worldwide. Timely decision-making that enables implementation of the most appropriate therapy or therapies is essential for achieving the best clinical outcomes in breast cancer. While clinicopathologic characteristics and immunohistochemistry have traditionally been used in decision-making, these clinical and laboratory parameters may be difficult to ascertain or be equivocal due to tumor heterogeneity. Tumor heterogeneity is described as a phenomenon characterized by spatial or temporal phenotypic variations in tumor characteristics. Spatial variations occur within tumor lesions or between lesions at a single time point while temporal variations are seen as tumor lesions evolve with time. Due to limitations associated with immunohistochemistry (which requires invasive biopsies), whole-body molecular imaging tools such as standard-of-care [18F]FDG and [18F]FES PET/CT are indispensable in addressing this conundrum. Despite their proven utility, these standard-of-care imaging methods are often unable to image a myriad of other molecular pathways associated with breast cancer. This has stimulated interest in the development of novel radiopharmaceuticals targeting other molecular pathways and processes. In this review, we discuss validated and potential roles of these standard-of-care and novel molecular approaches. These approaches' relationships with patient clinicopathologic and immunohistochemical characteristics as well as their influence on patient management will be discussed in greater detail. This paper will also introduce and discuss the potential utility of novel PARP inhibitor-based radiopharmaceuticals as non-invasive biomarkers of PARP expression/upregulation.

Prognostic Value of PSMA PET/CT in Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the majority of prostate cancer (PCa). PSMA has an enzymatic function that makes metabolic substrates such as folate available for utilization by PCa cells. Intracellular folate availability drives aggressive tumor phenotype. PSMA expression is, therefore, a marker of aggressive tumor biology. The large extracellular domain of PSMA is available for targeting by diagnostic and therapeutic radionuclides, making it a suitable cellular epitope for theranostics. PET imaging of radiolabeled PSMA ligands has several prognostic utilities. In the prebiopsy setting, intense PSMA avidity in a prostate lesion correlate well with clinically significant PCa (csPCa) on histology. When used for staging, PSMA PET imaging outperforms conventional imaging for the accurate staging of primary PCa, and findings on imaging predict post-treatment outcomes. The biggest contribution of PSMA PET imaging to PCa management is in the biochemical recurrence setting, where it has emerged as the most sensitive imaging modality for the localization of PCa recurrence by helping to guide salvage therapy. PSMA PET obtained for localizing the site of recurrence is prognostic, such that a higher lesion number predicts a less favorable outcome to salvage radiotherapy or surgical intervention. Systemic therapy is given to patients with advanced PCa with distant metastasis. PSMA PET is useful for predicting response to treatments with chemotherapy, first- and second-line androgen deprivation therapies, and PSMA-targeted radioligand therapy. Artificial intelligence using machine learning algorithms allows for the mining of information from clinical images not visible to the human eyes. Artificial intelligence applied to PSMA PET images, therefore, holds great promise for prognostication in PCa management.

Correlation between [68Ga]Ga-FAPI-46 PET Imaging and HIF-1α Immunohistochemical Analysis in Cervical Cancer: Proof-of-Concept

Hypoxia leads to changes in tumor microenvironment (upregulated CAFs) with resultant aggressiveness. A key factor in the physiological response to hypoxia is hypoxia-inducible factor-1alpha (HIF-1α). [68Ga]Ga-FAPI PET imaging has been demonstrated in various cancer types. We hypothesized that [68Ga]Ga-FAPI PET may be used as an indirect tracer for mapping hypoxia by correlating the image findings to pathological analysis of HIF-1α expression. The [68Ga]Ga-FAPI PET/CT scans of women with cancer of the cervix were reviewed and the maximum and mean standardized uptake value (SUVmax and SUVmean) and FAPI tumor volume (FAPI-TV) were documented. Correlation analysis was performed between PET-derived parameters and immunohistochemical staining as well as between PET-derived parameters and the presence of metastasis. Ten women were included. All patients demonstrated tracer uptake in the primary site or region of the primary. All patients had lymph node metastases while only six patients had distant visceral or skeletal metastases. The mean SUVmax, SUVmean, and FAPI-TV was 18.89, 6.88, and 195.66 cm3, respectively. The average FAPI-TV for patients with additional sites of metastases was higher than those without. Immunohistochemistry revealed varying intensities of HIF-1α expression in all tested samples. There was a positive correlation between the presence of skeletal metastases and staining for HIF-1α (r=0.80;p=0.017). The presence of skeletal metastasis was correlated to the HIF-1⍺ staining (percentage distribution). Furthermore, the FAPI-TV was a better predictor of metastatic disease than the SUVmax.

Recent Innovations and Nano-Delivery of Actinium-225: A Narrative Review

The actinium-225 (²²⁵Ac) radioisotope exhibits highly attractive nuclear properties for application in radionuclide therapy. However, the ²²⁵Ac radionuclide presents multiple daughter nuclides in its decay chain, which can escape the targeted site, circulate in plasma, and cause toxicity in areas such as kidneys and renal tissues. Several ameliorative strategies have been devised to circumvent this issue, including nano-delivery. Alpha-emitting radionuclides and nanotechnology applications in nuclear medicine have culminated in major advancements that offer promising therapeutic possibilities for treating several cancers. Accordingly, the importance of nanomaterials in retaining the ²²⁵Ac daughters from recoiling into unintended organs has been established. This review expounds on the advancements of targeted radionuclide therapy (TRT) as an alternative anticancer treatment. It discusses the recent developments in the preclinical and clinical investigations on ²²⁵Ac as a prospective anticancer agent. Moreover, the rationale for using nanomaterials in improving the therapeutic efficacy of α-particles in targeted alpha therapy (TAT) with an emphasis on ²²⁵Ac is discussed. Quality control measures in the preparation of ²²⁵Ac-conjugates are also highlighted.

Tachykinin Receptor-Selectivity of the Potential Glioblastoma-Targeted Therapy, DOTA-[Thi8,Met(O2)11]-Substance P

Radiopharmaceutical development hinges on the affinity and selectivity of the biological component for the intended target. An analogue of the neuropeptide Substance P (SP), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-[Thi8,Met(O2)11]-SP (DOTA-[Thi8,Met(O2)11]SP), in the theranostic pair [68Ga]Ga-/ [213Bi]Bi-DOTA-[Thi8,Met(O2)11]SP has shown promising clinical results in the treatment of inoperable glioblastoma. As the theranostic targeting component, modifications to SP that affect the selectivity of the resulting analogue for the intended target (neurokinin-1 receptor [NK1R]) could be detrimental to its therapeutic potential. In addition to other closely related tachykinin receptors (neurokinin-2 receptor [NK2R] and neurokinin-3 receptor [NK3R]), SP can activate a mast cell expressed receptor Mas-related G protein-coupled receptor subtype 2 (MRGPRX2), which has been implicated in allergic-type reactions. Therefore, activation of these receptors by SP analogues has severe implications for their therapeutic potential. Here, the receptor selectivity of DOTA-[Thi8,Met(O2)11]SP was examined using inositol phosphate accumulation assay in HEK293-T cells expressing NK1R, NK2R, NK3R or MRGPRX2. DOTA-[Thi8,Met(O2)11]SP had similar efficacy and potency as native SP at NK1R, but displayed greater NK1R selectivity. DOTA-[Thi8,Met(O2)11]SP was unable to elicit significant activation of the other tachykinin receptors nor MRGPRX2 at high concentrations nor did it display antagonistic behaviour at these receptors. DOTA-[Thi8,Met(O2)11]SP, therefore has high potency and selectivity for NK1R, supporting its potential for targeted theranostic use in glioblastoma multiforme and other conditions characterised by NK1R overexpression.

Imaging of Invasive Fungal Infections- The Role of PET/CT

Over the last decades, the population at risk for invasive fungal disease (IFD) has increased because of medical therapy advances and diseases compromising patients' immune systems. The high morbidity and mortality associated with invasive fungal disease in the immunocompromised present the challenge of early diagnosis of the IFD and the need to closely monitor the infection during treatment. The definitive diagnosis of invasive fungal disease based on culture or histopathological methods often has reduced diagnostic accuracy in the immunocompromised and may be very invasive. Less invasive and indirect evidence of the fungal infection by serology and imaging has been used for the early diagnosis of fungal infection before definitive results are available or when the definitive methods of diagnosis are suboptimal. Imaging in invasive fungal disease is a non-invasive biomarker that helps in the early diagnosis of invasive fungal disease but helps follow-up the infection during treatment. Different imaging modalities are used in the workup to evaluate fungal disease. The different imaging modalities have advantages and disadvantages at different sites in the body and may complement each other in the management of IFD. Positron emission tomography integrated with computed tomography with [18F]Fluorodeoxyglucose (FDG PET/CT) has helped manage IFD. The combined functional data from PET and anatomical data from the CT from almost the whole body allows noninvasive evaluation of IFD and provides a semiquantitative means of assessing therapy. FDG PET/CT adds value to anatomic-based only imaging modalities. The nonspecificity of FDG uptake has led to the evaluation of other tracers in the assessment of IFD. However, these are mainly still at the preclinical level and are yet to be translated to humans. FDG PET/CT remains the most widely evaluated radionuclide-based imaging modality in IFD management. The limitations of FDG PET/CT must be well understood, and more extensive prospective studies in uniform populations are needed to validate its role in the management of IFD that can be international guidelines.

Molecular Imaging of Tuberculosis

Despite the introduction of many novel diagnostic techniques and newer treatment agents, tuberculosis (TB) remains a major cause of death from an infectious disease worldwide. With about a quarter of humanity harboring Mycobacterium tuberculosis, the causative agent of TB, the current efforts geared towards reducing the scourge due to TB must be sustained. At the same time, newer alternative modalities for diagnosis and treatment response assessment are considered. Molecular imaging entails the use of radioactive probes that exploit molecular targets expressed by microbes or human cells for imaging using hybrid scanners that provide both anatomic and functional features of the disease being imaged. Fluorine-18 fluorodeoxyglucose (FDG) is the most investigated radioactive probe for TB imaging in research and clinical practice. When imaged with positron emission tomography interphase with computed tomography (PET/CT), FDG PET/CT performs better than sputum conversion for predicting treatment outcome. At the end of treatment, FDG PET/CT has demonstrated the unique ability to identify a subset of patients declared cured based on the current standard of care but who still harbor live bacilli capable of causing disease relapse after therapy discontinuation. Our understanding of the pathogenesis and evolution of TB has improved significantly in the last decade, owing to the introduction of FDG PET/CT in TB research. FDG is a non-specific probe as it targets the host inflammatory response to Mycobacterium tuberculosis, which is not specifically different in TB compared with other infectious conditions. Ongoing efforts are geared towards evaluating the utility of newer probes targeting different components of the TB granuloma, the hallmark of TB lesions, including hypoxia, neovascularization, and fibrosis, in TB management. The most exciting category of non-FDG PET probes developed for molecular imaging of TB appears to be radiolabeled anti-tuberculous drugs for use in studying the pharmacokinetic characteristics of the drugs. This allows for the non-invasive study of drug kinetics in different body compartments concurrently, providing an insight into the spatial heterogeneity of drug exposure in different TB lesions. The ability to repeat molecular imaging using radiolabeled anti-tuberculous agents also offers an opportunity to study the temporal changes in drug kinetics within the different lesions during treatment.

PET/CT features of a novel gallium-68 labelled hypoxia seeking agent in patients diagnosed with tuberculosis: a proof-of-concept study

INTRODUCTION

Positron emission tomography/computed tomography (PET/CT) in infection and inflammation has yielded promising results across a range of radiopharmaceuticals. In particular, PET/CT imaging of tuberculosis (TB) allows for a better understanding of this complex disease by providing insights into molecular processes within the TB microenvironment. TB lesions are hypoxic with research primarily focussed on cellular processes occurring under hypoxic stress. With the development of hypoxia seeking PET/CT radiopharmaceuticals, that can be labelled in-house using a germanium-68/gallium-68 (68Ge/68Ga) generator, a proof-of-concept for imaging hypoxia in TB is presented.

METHODS

Ten patients diagnosed with TB underwent whole-body PET/CT imaging, 60-90 min after intravenous administration of 74-185 MBq (2-5 mCi) 68Ga-nitroimidazole. No oral or intravenous contrast was administered. Images were visually and semiquantitatively assessed for abnormal 68Ga-uptake in the lungs.

RESULTS

A total of 28 lesions demonstrating hypoxic uptake were identified. Low- to moderate-uptake was seen in nodules, areas of consolidation and cavitation as well as effusions. The mean standard uptake value (SUVmean) of the lesions was 0.47 (IQR, 0.32-0.82) and SUVmax was 0.71 (IQR, 0.41-1.11). The lesion to muscle ratio (median, 1.70; IQR, 1.15-2.31) was higher than both the left ventricular and the aorta lesion to blood ratios.

CONCLUSION

Moving towards the development of unique host-directed therapies (HDT), modulation of oxygen levels may improve therapeutic outcome by reprogramming TB lesions to overcome hypoxia. This proof-of-concept study suggests that hypoxia in TB lesions can be imaged and quantified using 68Ga-nitroimidazole PET/CT. Subsequently, hypoxic load can be estimated to inform personalised treatment plans of patients diagnosed with TB.

68 Ga-nitroimidazole PET/CT imaging of hypoxia in tuberculosis: A case series

Tuberculosis (TB) lesions in humans have been proven to be severely hypoxic with hypoxia leading to latency and dormancy of disease. Dormant TB lesions become less susceptible to standard TB treatment regimens with varying responses to treatment but may have increased susceptibility to nitroimidazole drugs. This in turn implies that positron emission tomography / computed tomography (PET/CT) imaging with radiolabelled nitroimidazoles may identify patients who will benefit from treatment with antimicrobial agents that are active against anaerobic bacteria. This case series aims to highlight the hypoxic uptake and retention of a novel ⁶⁸ Ga-labelled hypoxia-seeking agent in TB lesions at different time points during anti-TB therapy using PET/CT imaging. Patients with confirmed TB underwent whole-body PET/CT after administration of a ⁶⁸ Ga-nitroimidazole derivative at baseline and follow-up. Images were analysed both qualitatively and semi-quantitatively. Hypoxic uptake and change in uptake over time were analysed using lesion-to-muscle ratio (LMR) and lesion-to-blood ratio (LBR). ⁶⁸ Ga-nitroimidazole avid lesions were demonstrated most frequently in the upper lobes of the lung. Low-grade hypoxic uptake was visualised in areas of consolidation, cavitation, nodules and lymph nodes. From baseline to follow-up imaging, the LMR increased with persistent hypoxic load despite morphologic improvement. This case series highlights the dynamic hypoxic microenvironment in TB lesions. From these initial data, it appears that ⁶⁸ Ga-nitroimidazole is a promising candidate for monitoring hypoxic load in patients diagnosed with TB. Such imaging could identify patients who would benefit from individualised therapy targeting other mechanisms in the TB microenvironment with the intention to predict or improve treatment response.

[68Ga]Ga-NODAGAZOL uptake in atherosclerotic plaques correlates with the cardiovascular risk profile of patients

OBJECTIVES

This study aimed to determine the correlation of [⁶⁸Ga]Ga-NODAGA^ZOL uptake in atherosclerotic plaques and the cardiovascular risk profile of patients imaged with positron emission tomography (PET), wherein quantification of uptake was determined by atherosclerotic plaque maximum target-to-background ratio (TBRmax). We also correlated uptake with a history of cardiovascular events.

METHODS

We included patients who underwent PET/CT imaging post-injection of [⁶⁸Ga] Ga-NODAGA^ZOL. We documented the number of atherosclerotic plaques found in the major arteries on CT and the cardiovascular risks in each patient. We quantified the intensity of tracer uptake in atherosclerotic plaque in the major arteries using the maximum standardized uptake value (SUVmax). The SUVmax of the most tracer-avid plaque was documented as representative of the individual arterial bed. We determined background vascular tracer activity using the mean standardized uptake value (SUVmean) obtained from the lumen of the superior vena cava. The maximum target-to-background ratio (TBRmax) was calculated as a ratio of the SUVmax to the SUVmean. The TBRmax was correlated to the number of atherogenic risk factors and history of cardiovascular events.

RESULTS

Thirty-four patients (M: F 31:3; mean age ± SD: 63 ± 10.01 years) with ≥ 2 cardiovascular risk factors were included. Statistically significant correlation between TBRmax and the number of cardiovascular risk factors was noted in the right carotid (r = 0.50; p < 0.05); left carotid (r = 0. 649; p < 0.05); ascending aorta (r = 0.375; p < 0.05); aortic arch (r = 0.483; p < 0.05); thoracic aorta (r = 0.644; p < 0.05); left femoral (r = 0.552; p < 0.05) and right femoral arteries (r = 0.533; p < 0.05). TBRmax also demonstrated a positive correlation to history of cardiovascular event in the right carotid (U = 26.00; p < 0.05); left carotid (U = 11.00; p < 0.05); ascending aorta (U = 49.00; p < 0.05); aortic arch (U = 37.00; p < 0.05); thoracic aorta (U = 16.00; p < 0.05); left common iliac (U = 49.500; p < 0.05), right common iliac (U = 43.00; p < 0.05), left femoral (U = 40.500; p < 0.05) and right femoral (U = 37.500; p < 0.05).

CONCLUSION

In this cohort of patients, a positive correlation was noted between atherosclerotic plaque uptake of [⁶⁸Ga]Ga-NODAGA^ZOL and the number of atherogenic risk factors which translates to the risk of atherosclerosis and cardiovascular risk factors.

Correlation Between CT Features of Active Tuberculosis and Residual Metabolic Activity on End-of-Treatment FDG PET/CT in Patients Treated for Pulmonary Tuberculosis

Patients who complete a standard course of anti-tuberculous treatment (ATT) for pulmonary tuberculosis and are declared cured according to the current standard of care commonly have residual metabolic activity (RMA) in their lungs on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PER/CT) imaging. RMA seen in this setting has been shown to be associated with relapse of tuberculosis. The routine clinical use of FDG PET/CT imaging for treatment response assessment in tuberculosis is hindered by cost and availability. CT is a more readily available imaging modality. We sought to determine the association between CT features suggestive of active tuberculosis and RMA on FDG PET/CT obtained in patients who completed a standard course of ATT for pulmonary tuberculosis. We prospectively recruited patients who completed a standard course of ATT and declared cured based on negative sputum culture. All patients had FDG PET/CT within 2 weeks of completing ATT. We determined the presence of RMA on FDG PET images. Among the various lung changes seen on CT, we considered the presence of lung nodule, consolidation, micronodules in tree-in-bud pattern, FDG-avid chest nodes, and pleural effusion as suggestive of active tuberculosis. We determine the association between the presence of RMA on FDG PET and the CT features of active tuberculosis. We include 75 patients with a mean age of 36.09 ± 10.49 years. Forty-one patients (54.67%) had RMA on their FDG PET/CT while 34 patients (45.33%) achieved complete metabolic response to ATT. There was a significant association between four of the five CT features of active disease, p < 0.05 in all cases. Pleural effusion (seen in two patients) was the only CT feature of active disease without a significant association with the presence of RMA. This suggests that CT may be used in lieu of FDG PET/CT for treatment response assessment of pulmonary tuberculosis.

Cardiovascular disturbances in COVID-19: an updated review of the pathophysiology and clinical evidence of cardiovascular damage induced by SARS-CoV-2

Severe acute respiratory coronavirus-2 (SARS-Co-2) is the causative agent of coronavirus disease-2019 (COVID-19). COVID-19 is a disease with highly variable phenotypes, being asymptomatic in most patients. In symptomatic patients, disease manifestation is variable, ranging from mild disease to severe and critical illness requiring treatment in the intensive care unit. The presence of underlying cardiovascular morbidities was identified early in the evolution of the disease to be a critical determinant of the severe disease phenotype. SARS-CoV-2, though a primarily respiratory virus, also causes severe damage to the cardiovascular system, contributing significantly to morbidity and mortality seen in COVID-19. Evidence on the impact of cardiovascular disorders in disease manifestation and outcome of treatment is rapidly emerging. The cardiovascular system expresses the angiotensin-converting enzyme-2, the receptor used by SARS-CoV-2 for binding, making it vulnerable to infection by the virus. Systemic perturbations including the so-called cytokine storm also impact on the normal functioning of the cardiovascular system. Imaging plays a prominent role not only in the detection of cardiovascular damage induced by SARS-CoV-2 infection but in the follow-up of patients' clinical progress while on treatment and in identifying long-term sequelae of the disease.

Elevated Levels of Soluble CTLA-4, PD-1, PD-L1, LAG-3 and TIM-3 and Systemic Inflammatory Stress as Potential Contributors to Immune Suppression and Generalized Tumorigenesis in a Cohort of South African Xeroderma Pigmentosum Patients

Xeroderma Pigmentosum (XP), an autosomal recessive disorder characterized by ultraviolet radiation-induced abnormalities of DNA excision and repair pathways is associated with early development of cutaneous cancers. Intracellular oxidative stress has also been proposed as a contributor to the occurrence of skin cancers. However, little is known about the possible augmentative contributions of chronic inflammation, immune suppression and oxidative stress to the pathogenesis of malignancies associated with other subtypes of XP. This has been addressed in the current study, focused on the measurement of systemic biomarkers of inflammation, immune dysfunction and oxidative damage in XP patients, consisting of XP-C, XP-D and XP-E cases, including those XP-C cases who had already developed multiple skin malignancies. The inflammatory biomarker profile measured in XP patients and healthy control subjects included the cytokines, interleukins (ILs)-2, -4, -6, -10, interferon-γ (IFN- γ) and tumor-necrosis factor-α (TNF-α), the acute phase reactant, C-reactive protein (CRP), and cotinine (as an objective indicator of smoking status). Immune suppression was detected according to the levels of five soluble inhibitory immune checkpoint proteins (CTLA-4, PD-1, PD-L1, LAG-3 and TIM-3), as well as those of vitamin D, while oxidative stress was determined according to the circulating levels of the DNA adduct, 8-hydroxy-2-deoxyguanosine (8-OH-dG). These various biomarkers were measured in plasma using immunofluorimetric, nephelometric and ELISA procedures. Significant elevations in IL-6 (P<0.01) and TNF-α (P<0.0001), but none of the other cytokines, as well as increased levels of all five soluble inhibitory immune checkpoints (P=0.032-P=0.0001) were detected in the plasma of the XP patients. C-reactive protein and vitamin D were increased and decreased, respectively (both P<0.0001), while only one participant had an elevated level of plasma cotinine. Surprisingly, the levels of 8-OH-dG were significantly (P=0.0001) lower in the group of XP patients relative to a group of healthy control subjects. The findings of increased levels of pro-inflammatory cytokines and, in particular, those of the soluble immune checkpoints, in the setting of decreased vitamin D and moderately elevated levels of CRP in XP patients suggest a possible secondary role of ongoing, inflammatory stress and immune suppression in the pathogenesis of XP-associated malignancies.

18F-FDG-PET/CT imaging of uterine cervical cancer recurrence in women with and without HIV infection

BACKGROUND

To compare the rate, time and, pattern of recurrence of cervical cancer between patients with and without HIV infection and to determine factors predicting cervical cancer recurrence in patients evaluated by ¹⁸F-FDG-PET/CT.

METHODS

We reviewed the ¹⁸F-FDG-PET/CT images of patients with histologically proven cervical carcinoma who were presenting with suspected recurrence. We extracted epidemiologic data, previous treatment, histologic subtype, HIV status, viral load and CD4 counts from the electronic laboratory database and the referral form for the ¹⁸F-FDG-PET/CT study.

RESULTS

We studied 303 women including 112 HIV-infected patients. FIGO stage III disease was present in 131 patients. Of 198 patients with recurrence, 74 were HIV-infected while 124 were not (P=0.849). HIV infected patients were younger (41.99±9.30 years) compared to HIV-uninfected (50.19±11.09), P<0.001. Local recurrence was present in 125 patients while 100 patients had a distant recurrence. Recurrence occurred at a single site in 88 patients and two or more sites in 110 patients. No significant difference in the recurrent patterns between HIV-infected and uninfected patients. Median time to recurrence was 10.50 months (range: 6.00-156.00) among HIV-infected versus 12.00 months (IQR:7.00-312.00) among the uninfected, P=0.065. FIGO stage III (P=0.042) and the presence of histological sub-types other than SCC (P=0.005) were significant predictors of recurrence. HIV infection by itself was not significant in predicting recurrence (P=0.843).

CONCLUSIONS

HIV infection has no significant impact on the rate, time or pattern of recurrence in women with suspected cervical carcinoma recurrence. Advanced disease and histological variant other than SCC are predictive of recurrence.

The Use of 18F-FDG PET/CT Metabolic Parameters in Predicting Overall Survival in Patients Undergoing Restaging for Malignant Melanoma

Malignant melanoma is one of the more aggressive cancers in the skin, with an increasing incidence every year. Melanoma has a better prognosis if diagnosed early and survival tends to decrease once the disease has metastasized. Positron emission tomography (PET) with 2-[¹⁸F]fluoro-2-deoxy-D-glucose (¹⁸F-FDG) has been used extensively over the past two decades in staging and assessing responses to therapy in patients with melanoma. Metabolic PET parameters have been demonstrated to be independent prognostic factors for progression-free survival (PFS) and overall survival (OS) in different malignancies, melanoma included. In our study, we evaluated the metabolic parameters of ¹⁸F-FDG PET/CT (flourodeoxyglucose positron emission tomography/computed tomography) in predicting the overall survival in patients with malignant melanoma who presented for restaging. Metabolic PET parameters (maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG)) of the primary tumor, as well as whole-body MTV and TLG of the metastatic disease, were measured. Survival curves for OS were constructed and mortality rates were determined using the different PET variables. Forty-nine patients who presented for a PET/CT restaging in melanoma were included in this study. We found that non-survivors had significantly higher median MTV (11.86 cm³ vs. 5.68 cm³; p-value = 0.022), TLG (3125 vs. 14; p-value = 0.0357), whole-body MTV (53.9 cm³ vs. 14.4 cm³; p-value = 0.0076) and whole-body TLG (963.4 vs. 114.6; p-value = 0.0056). This demonstrated that high MTV and TLG values of the primary tumor and whole-body TLG as quantified by ¹⁸F-FDG PET/CT were prognostic factors for overall survival. The findings may potentially guide clinicians in decision making and identifying patients with a poorer prognosis.

A Prospective Investigation of Tumor Hypoxia Imaging with 68Ga-Nitroimidazole PET/CT in Patients with Carcinoma of the Cervix Uteri and Comparison with 18F-FDG PET/CT: Correlation with Immunohistochemistry

Hypoxia in cervical cancer has been associated with a poor prognosis. Over the years ⁶⁸Ga labelled nitroimidazoles have been studied and have shown improved kinetics. We present our initial experience of hypoxia Positron Emission Tomography (PET) imaging in cervical cancer with ⁶⁸Ga-Nitroimidazole derivative and the correlation with ¹⁸F-FDG PET/CT and immunohistochemistry. Twenty women with cervical cancer underwent both ¹⁸F-FDG and ⁶⁸Ga-Nitroimidazole PET/CT imaging. Dual-point imaging was performed for ⁶⁸Ga-Nitroimidazole PET. Immunohistochemical analysis was performed with hypoxia inducible factor-1α (HIF-1α). We documented SUVmax, SUVmean of the primary lesions as well as tumor to muscle ratio (TMR), tumor to blood (TBR), metabolic tumor volume (MTV) and hypoxic tumor volume (HTV). There was no significant difference in the uptake of ⁶⁸Ga-Nitroimidazole between early and delayed imaging. Twelve patients had uptake on ⁶⁸Ga-Nitroimidazole PET. Ten patients demonstrated varying intensities of HIF-1α expression and six of these also had uptake on ⁶⁸Ga-Nitroimidazole PET. We found a strong negative correlation between HTV and immunohistochemical staining (r = −0.660; p = 0.019). There was no correlation between uptake on PET imaging and immunohistochemical analysis with HIF-1α. Two-thirds of the patients demonstrated hypoxia on ⁶⁸Ga-Nitroimidazole PET imaging.

Radionuclide imaging of hypoxia: Where are we now? Special attention to cancer of the cervix uteri

Cancer of the cervix is the fourth commonest malignancy in women worldwide and it also ranks fourth as the cause of cancer related mortality in women. Hypoxia is a common characteristic of solid tumours and cervical cancer is no exception. Hypoxia is associated with increased aggressiveness, risk of invasion and metastasis. Tumour hypoxia also results in resistance to both radiation therapy and chemotherapy leading to a poorer prognosis. In-vivo measurement of tumour hypoxia is vital in oncologic practice because it can predict outcome and identify patients with a worse prognosis. Mapping of tumour hypoxia may also help select patients that may benefit from applicable treatments. While traditional methods of measuring hypoxia such as the Eppendorf probe is considered the gold standard, it is invasive and technically demanding. Non-invasive methods of measuring tumourhypoxia are ideal. Positron emission tomography/computed tomography (PET/CT) imaging with nitro-imidazole-based tracers is a highly sensitive nuclear imaging technique that is suited for non-invasive in vivo monitoring of hypoxia. Over the years various hypoxia specific PET tracers have been investigated in various malignancies including cancer of the cervix. Several fluorine-18 (¹⁸F)-based tracers have been studied and although most had small patient numbers, the results are promising and generally demonstrate an associate between the presence of hypoxia and treatment outcome. The need for an onsite cyclotron and specialized radiopharmacy skills make these tracers unattractive and largely unavailable for routine clinical applications. With the increase in availability of the gallium-68 (⁶⁸Ga) generator this makes the ⁶⁸Ga-labelled nitroimidazole derivatives attractive because ⁶⁸Ga is available from a generator with a shelf life of almost a year. The chemistry of ⁶⁸Ga makes for easy labelling with several peptides and molecules. Pre-clinical work has demonstrated the feasibility of using these tracers for imaging hypoxia and has laid the groundwork for further human studies with these tracers.The aim of this review is to discuss hypoxia and its impact in cancer of the cervix as well as to look into the progress made in hypoxia imaging in cancer of the cervix. This will focus on the tracers studied thus far and some of the challenges of hypoxia imaging.

A comparison of the diagnostic performance of 18F-PSMA-1007 and 68GA-PSMA-11 in the same patients presenting with early biochemical recurrence

OBJECTIVE

Accurate early assessment of biochemical recurrence is essential in determining the correct treatment plan for patients with prostate cancer. Gallium-68-prostate-specific membrane antigen-11 (⁶⁸Ga-PSMA-11) targeting PSMA has been at the forefront of imaging in biochemical recurrence however the emergence of fluorine-18 (¹⁸F)-PSMA-1007 may prove to be advantageous over the ⁶⁸Ga-PSMA-11 molecule due to its physical and physiologic al attributes. The aim of our study was to assess the diagnostic performance of ¹⁸F-PSMA-1007 as compared to that of ⁶⁸Ga-PSMA-11 in the same patients who presented with biochemical recurrence.

MATERIAL AND METHODS

Twenty-one patients with biochemical recurrence prostate cancer were prospectively enrolled into the study. Fluorine-18-PSMA-1007 positron emission tomography/computed tomography (PET/CT) was performed on the same patient after ⁶⁸Ga-PSMA-11 PET/CT had been performed. Recurrence diagnosed on each of these studies was compared against a final diagnosis based on clinical follow-up and histological correlation where available.

RESULTS

Gallium-68-PSMA-11 identified fifteen (71,4%) patients as being negative for recurrence whilst five (23.8%) were identified as positive and one (4.8%) as uncertain. In comparison ¹⁸F-PSMA-1007 identified eight (38.1%) as being positive with thirteen (61.9%) patients' scans identified as negative for recurrence. No scans were classified as uncertain for the ¹⁸F-PSMA-1007 group. Fluorine-18-PSMA-1007 identified 8 lesions as positive for disease recurrence whilst only 6 lesions were identified on ⁶⁸Ga-PSMA-11. Of the 8 patients identified as having recurrence on ¹⁸F-PSMA-1007 4 of those demonstrated local prostatic recurrence. The rest demonstrated local nodal recurrence and skeletal metastases. Fluorine-18-PSMA-1007 demonstrated a sensitivity, specificity, positive and negative predictive value of 88.9%, 100%, 100%, and 92.3% respectively whilst ⁶⁸Ga-PSMA-11 demonstrated a sensitivity, specificity, positive and negative predictive value of 44.4%, 83.3%, 80%, and 66.6%, respectively.

CONCLUSION

In our pilot study ¹⁸F-PSMA-1007 was able to detect more sites of recurrence as compared to ⁶⁸Ga-PSMA-11 which were mainly within the prostate and surrounding pelvic structures.

Pattern of Prostate Cancer Recurrence Assessed by 68Ga-PSMA-11 PET/CT in Men Treated with Primary Local Therapy

Imaging plays a vital role in detecting the recurrence of prostate cancer (PCa) to guide the choice of salvage therapy. Gallium-68 prostate-specific membrane antigen positron-emission tomography/computed tomography (⁶⁸Ga-PSMA-11 PET/CT) is useful for detecting PCa recurrence. We assessed the pattern of PCa recurrence stratified by serum prostate-specific antigen level and type of primary local treatment in men with biochemical recurrence (BCR) after primary local therapy with radical prostatectomy or external beam radiotherapy (EBRT) using ⁶⁸Ga-PSMA-11 PET/CT. We reviewed patients imaged with ⁶⁸Ga-PSMA-11 PET/CT for the localization of the site of PCa recurrence. We determined the site and number of lesions due to PCa recurrence at different PSA levels. A total of 247 men (mean age of 65.72 ± 7.51 years and median PSA of 2.70 ng/mL (IQR = 0.78–5.80)) were included. ⁶⁸Ga-PSMA-11 PET/CT detected the site of recurrence in 81.4% of patients with a median number of lesions per patient of 1 (range = 1–5). ⁶⁸Ga-PSMA-11 PET/CT positivity was 43.6%, 75.7%, 83.3%, 90.0%, and 95.8% at PSA levels of <0.5, 0.5–1.0., 1.1–2.0, 2.1–5.0, and 5.0–10.0, respectively. The most common site of recurrence was in the prostate gland/bed at all PSA levels. Pelvic, extra-pelvic, and combined pelvic and extra-pelvic sites of recurrence were seen in 118, 50, and 33 patients, respectively. The risk of extra-pelvic recurrence increases with rising PSA levels. ⁶⁸Ga-PSMA-11 PET/CT has a high lesion detection rate for biochemical recurrence of PCa in patients previously treated with primary local therapy.

Towards Facile Radiolabeling and Preparation of Gallium-68-/Bismuth-213-DOTA-[Thi8, Met(O2)11]-Substance P for Future Clinical Application: First Experiences

Substance P (SP) is a small peptide commonly known as a preferential endogenous ligand for the transmembrane neurokinin-1 receptor. Nuclear Medicine procedures currently involve radiolabeled SP derivatives in peptide radioligand endotherapy of inoperable glioblastoma. Promising clinical results sparked the demand for facile production strategies for a functionalized 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-[Thi⁸, Met(O₂)¹¹]-SP to allow for rapid Gallium-68 or Bismuth-213 complexation. Therefore, we provide a simple kit-like radiotracer preparation method that caters for the gallium-68 activity eluted from a SnO₂ generator matrix as well as preliminary results on the adaptability to produce [²¹³Bi]Bi-DOTA-[Thi⁸, Met(O₂)¹¹]SP from the same vials containing the same starting material. Following a phase of radioanalysis for complexation of gallium-68 to DOTA-[Thi⁸, Met(O₂)¹¹]SP and assessing the radiolabeling parameters, the vials containing appropriate kit-prototype material were produced in freeze-dried batches. The facile radiolabeling performance was tested and parameters for future human application were calculated to meet the criteria for theranostic loco-regional co-administration of activity doses comprising [⁶⁸Ga]Ga-DOTA-[Thi⁸, Met(O₂)¹¹]SP mixed with [²¹³Bi]Bi-DOTA-[Thi⁸, Met(O₂)¹¹]SP. [⁶⁸Ga]Ga-DOTA-[Thi⁸, Met(O₂)¹¹]SP was prepared quantitatively from lyophilized starting material within 25 min providing the required molar activity (18 ± 4 GBq/µmol) and activity concentration (98 ± 24 MBq/mL), radiochemical purity (>95%) and sustained radiolabeling performance (4 months at >95% LE) as well as acceptable product quality (>95% for 120 min). Additionally, vials of the same starting materials were successfully adapted to a labeling strategy available for preparation of [²¹³Bi]Bi-DOTA-[Thi⁸, Met(O₂)¹¹]SP providing sufficient activity for 1-2 human doses. The resultant formulation of [⁶⁸Ga]Ga-/[²¹³Bi]Bi-DOTA-[Thi⁸, Met(O₂)¹¹]SP activity doses was considered of adequate radiochemical quality for administration. This investigation proposes a simple kit-like formulation of DOTA-[Thi⁸, Met(O₂)¹¹]SP-a first-line investigation into a user friendly, straightforward tracer preparation that would warrant efficient clinical investigations in the future. Quantitative radiolabeling was accomplished for [⁶⁸Ga]Ga-DOTA-[Thi⁸, Met(O₂)¹¹]SP and [²¹³Bi]Bi-DOTA-[Thi⁸, Met(O₂)¹¹]SP preparations; a key requirement when addressing the specific route of catheter-assisted co-injection directly into the intratumoral cavities.

Single Photon Emission Tomography in the Diagnostic Assessment of Cardiac and Vascular Infectious Diseases

Cardiac and vascular infection is an arising cause of mortality and morbidity in the adult population. Diagnosis based on culture and anatomic imaging are frequently inconclusive. Radiolabeled leucocyte scintigraphy plays a useful role in the diagnosis and management of these serious infectious conditions. In this paper, we present an update on the diagnostic performance of single- photon emission tomographic (SPECT) techniques using different radionuclides in the management of patients with cardiac and vascular infections. We performed a thorough search of recent literature on the topic. We present a discussion on the clinical utility of different SPECT tracers in cardiac and vascular infections, including infective endocarditis, cardiac implantable electronic device (CIED) infections, left ventricular assist device infection, and vascular graft infection. Radionuclide technique using SPECT tracers is a useful imaging modality in the diagnosis of cardiac infection. Among the different SPECT tracers for infection imaging, radiolabeled leucocyte scintigraphy is currently the most useful tool in the diagnosis and management of patients with suspected cardiac and vascular infection. Radiolabeled leucocyte scintigraphy has a high specificity, a result of the ability of the leucocytes to accumulate as sites of pyogenic infection but not at sites of sterile inflammation such as seen in the early post-operative period or in response to the presence of a prosthetic cardiac or vascular material. Limited experience with radiotracers for in vivo labelling of leucocytes such as ^99mTc-sulesomab and ^99mTc-besilesomab show acceptable diagnostic performance without the need for the tedious process of ex-vivo labeling. ⁶⁷Ga scintigraphy used to be popular for cardiac and vascular infection imaging. Its use has run out of favor following the availability of more effective molecular imaging methods. SPECT techniques with radiolabeled leucocyte scintigraphy has a high diagnostic performance in the evaluation of patients with suspected cardiac or vascular infection. It is able to confirm or reject the presence of infection when results of anatomic imaging or culture remain inconclusive. Its diagnostic performance is not compromised by sterile inflammation occurring in the early post-operative period or in response to implanted prosthetic materials.

Impact of optimized PET imaging conditions on 18F-FDG uptake quantification in patients with apparently normal aortas

BACKGROUND

The cardiovascular committee of the European Association of Nuclear Medicine (EANM) recently published recommendations on imaging conditions to be observed during 18F-FDG PET imaging of vascular inflammation. This study aimed to evaluate the impact of applying these optimized imaging conditions on PET quantification of arterial 18F-FDG uptake.

METHODS AND RESULTS

Fifty-seven patients were prospectively recruited to undergo an early 18F-FDG PET/CT imaging at 60 minutes and repeat delayed imaging at ≥ 120 minutes post tracer injection. Routine oncologic 18F-FDG PET protocol was observed for early imaging, while delayed imaging parameters were optimized for vascular inflammation imaging as recommended by the EANM. Aortic SUVmax of the ascending aorta and SUVmean from the lumen of the superior vena cava (SVC SUVmean) were obtained on early and delayed imaging. Target-to-background ratio (TBR) was obtained for the early and delayed imaging. Aortic SUVmax increased by a mean of 70%, while SVC SUVmean decreased by a mean of 52% between early and delayed imaging (P < 0.001). TBR increased by 122% following delayed imaging. TBR increased, while SVC SUVmean declined across all time-points from 120 to > 180 minutes. Aortic SUVmax significantly increased at imaging time-points between 120 and 180 minutes. No significant improvement in aortic SUVmax was seen at imaging time-points beyond 180 minutes.

CONCLUSIONS

18F-FDG PET imaging conditions optimized for vascular inflammation imaging lead to an improved quantification through an increase in the quantified vascular tracer uptake and decrease in blood-pool background activity.

Immune reconstitution inflammatory syndrome-associated Graves disease in HIV-infected patients: clinical characteristics and response to radioactive iodine therapy

OBJECTIVES

We aimed to describe the clinical characteristics and the response to radioactive iodine (RAI) treatment of immune reconstitution inflammatory syndrome-associated Graves disease (IRIS-GD) in comparison to Graves disease (GD) seen in HIV-uninfected patients.

METHODS

We retrospectively reviewed the medical records of patients treated with RAI for GD. We obtained clinical, biochemical and HIV-related information of patients from their medical records. We compared patient characteristics and response to RAI treatment between patients with IRIS-GD and GD seen in HIV-uninfected patients.

RESULTS

A total of 253 GD patients, including 51 patients with IRIS-GD, were included. Among IRIS-GD patients, CD4 cell nadir was 66 cells/µL (range: 37-103) with a peak HIV viral load of 60 900 copies/mL (range: 36 542-64 500). At the time of diagnosis of IRIS-GD, all patients had a completely suppressed HIV viraemia with a CD4 cell count of 729 cells/µL (range: 350-1279). The median interval between the commencement of HIV treatment and the onset of GD was 63 months. At 3 months follow-up, the proportion of patients with IRIS-GD achieving a successful RAI treatment outcome (euthyroid/hypothyroid state) was lower than that of HIV-uninfected patients (35.3% vs. 63.4%, respectively; p < 0.001). The response rate remained lower (60.8%) among patients with IRIS GD than among HIV-uninfected GD patients (80.2%, p = 0.004) at 6 months follow-up. After correcting for differences in age, gender and pre-treatment thyroid-stimulating hormone level, there was no significant difference in RAI treatment response between the two groups.

CONCLUSIONS

After correcting for possible confounders, the response to RAI treatment was not different between patients with IRIS-GD and GD in HIV-uninfected patients.

Global experience with PSMA-based alpha therapy in prostate cancer

Purpose

This review discusses the current state of prostate-specific membrane antigen (PSMA)-based alpha therapy of metastatic castration-resistant prostate cancer (mCRPC). With this in-depth discussion on the growing field of PSMA-based alpha therapy (PAT), we aimed to increase the interactions between basic scientists and physician–scientists in order to advance the field.

Methods

To achieve this, we discuss the potential, current status, and opportunities for alpha therapy and strategies, attempted to date, and important questions that need to be addressed. The paper reviews important concepts, including whom to treat, how to treat, what to expect regarding treatment outcome, and toxicity, and areas requiring further investigations.

Results

There is much excitement about the potential of this field. Much of the potential exists because these therapies utilize unique mechanisms of action, difficult to achieve with other conventional therapies.

Conclusion

A better understanding of the strengths and limitations of PAT may help in creating an effective therapy for mCRPC and design a rational combinatorial approach to treatment by targeting different tumor pathways.

Radionuclide Imaging of Fungal Infections and Correlation with the Host Defense Response

The human response to invading fungi includes a series of events that detect, kill, or clear the fungi. If the metabolic host response is unable to eliminate the fungi, an infection ensues. Some of the host response’s metabolic events to fungi can be imaged with molecules labelled with radionuclides. Several important clinical applications have been found with radiolabelled biomolecules of inflammation. ¹⁸F-fluorodeoxyglucose is the tracer that has been most widely investigated in the host defence of fungi. This tracer has added value in the early detection of infection, in staging and visualising dissemination of infection, and in monitoring antifungal treatment. Radiolabelled antimicrobial peptides showed promising results, but large prospective studies in fungal infection are lacking. Other tracers have also been used in imaging events of the host response, such as the migration of white blood cells at sites of infection, nutritional immunity in iron metabolism, and radiolabelled monoclonal antibodies. Many tracers are still at the preclinical stage. Some tracers require further studies before translation into clinical use. The application of therapeutic radionuclides offers a very promising clinical application of these tracers in managing drug-resistant fungi.

The Association of Tumor Burden by 18F-FDG PET/CT and Survival in Vulvar Carcinoma

PURPOSE

The aim of this study was to assess the impact of 18F-FDG PET/CT metabolic parameters obtained at initial staging of vulva carcinoma on survival in women with and without HIV infection.

PATIENTS AND METHODS

18F-FDG PET/CT images of women with vulva cancer who are planned for definitive therapy were analyzed. SUVmax, SUVmean, MTV, and total lesion glycolysis (TLG) as well as whole-body MTV and whole-body TLG were computed.

RESULTS

Twenty-five women were included with a mean age of 43.44 ± 10.32. The majority of the patients were HIV infected with a median CD4 count of 444.00 cells/mm3. The HIV-infected women are younger at diagnosis than their HIV-uninfected counterparts. All patients presented with inguinofemoral lymph node involvement, whereas half the patients had pelvic nodal metastasis. All the patients with distant visceral or skeletal metastasis were HIV infected. The lungs were the most common site of distant metastasis. When comparing the SUVmax, SUVmean, MTV, TLG, wbMTV, and wbTLG between HIV-infected and HIV-uninfected patients, we did not find statistical differences. Twelve patients (48%) were upstaged to metastatic disease. Seven patients had died at the time of analysis. The wbMTV and wbTLG were significantly higher in nonsurvivors than survivors.

CONCLUSIONS

18F-FDG PET/CT improves initial staging of squamous cell carcinoma among women with and without HIV infection. The whole-body tumor burden assessed by 18F-FDG PET metabolic metrics did not differ between HIV-infected and HIV-uninfected women. A higher whole-burden tumor burden is associated with a higher risk of mortality among women with vulva cancer.

Immune Checkpoints, Inhibitors and Radionuclides in Prostate Cancer: Promising Combinatorial Therapy Approach

Emerging research demonstrates that co-inhibitory immune checkpoints (ICs) remain the most promising immunotherapy targets in various malignancies. Nonetheless, ICIs have offered insignificant clinical benefits in the treatment of advanced prostate cancer (PCa) especially when they are used as monotherapies. Current existing PCa treatment initially offers an improved clinical outcome and overall survival (OS), however, after a while the treatment becomes resistant leading to aggressive and uncontrolled disease associated with increased mortality and morbidity. Concurrent combination of the ICIs with radionuclides therapy that has rapidly emerged as safe and effective targeted approach for treating PCa patients may shift the paradigm of PCa treatment. Here, we provide an overview of the contextual contribution of old and new emerging inhibitory ICs in PCa, preclinical and clinical studies supporting the use of these ICs in treating PCa patients. Furthermore, we will also describe the potential of using a combinatory approach of ICIs and radionuclides therapy in treating PCa patients to enhance efficacy, durable cancer control and OS. The inhibitory ICs considered in this review are cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1), V-domain immunoglobulin suppressor of T cell activation (VISTA), indoleamine 2,3-dioxygenase (IDO), T cell Immunoglobulin Domain and Mucin Domain 3 (TIM-3), lymphocyte-activation gene 3 (LAG-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT), B7 homolog 3 (B7-H3) and B7-H4.

An overview of the developments and potential applications of 68Ga-labelled PET/CT hypoxia imaging

Non-invasive imaging of hypoxia plays a role in monitoring the body's adaptive response or the development of pathology under hypoxic conditions. Various techniques to image hypoxia have been investigated with a shift towards the use of molecular imaging using PET/CT. The role of hypoxia-specific radiopharmaceuticals such as radiolabelled nitroimidazoles is well documented particularly in the oncologic setting. With the increasing utilisation of in-house labelling with a PET benchtop generator, such as the ⁶⁸Ge/⁶⁸Ga generator, the use of ⁶⁸Ga-labelled hypoxic radiopharmaceuticals in the clinical setting is developing. Since hypoxia plays a role in various pathologic states including infectious disease such as TB, there is a need to explore the potential application of ⁶⁸Ga-labelled hypoxia seeking radiopharmaceuticals beyond oncology. The purpose of this review is to describe the developments of ⁶⁸Ga-labelled hypoxic radiopharmaceuticals including the various chelators that have been investigated. Further, the role of hypoxia imaging in various pathologies is discussed with particular emphasis on the potential clinical applications of hypoxia PET/CT in TB.

[68Ga]Ga-Pentixafor for PET Imaging of Vascular Expression of CXCR-4 as a Marker of Arterial Inflammation in HIV-Infected Patients: A Comparison with 18F[FDG] PET Imaging

People living with human immunodeficiency virus (PLHIV) have excess risk of atherosclerotic cardiovascular disease (ASCVD). Arterial inflammation is the hallmark of atherogenesis and its complications. In this study we aimed to perform a head-to-head comparison of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) and Gallium-68 pentixafor positron emission tomography/computed tomography [68Ga]Ga-pentixafor PET/CT for quantification of arterial inflammation in PLHIV. We prospectively recruited human immunodeficiency virus (HIV)-infected patients to undergo [18F]FDG PET/CT and [68Ga]Ga-pentixafor PET/CT within two weeks of each other. We quantified the levels of arterial tracer uptake on both scans using maximum standardized uptake value (SUVmax) and target-background ratio. We used Bland and Altman plots to measure the level of agreement between tracer quantification parameters obtained on both scans. A total of 12 patients were included with a mean age of 44.67 ± 7.62 years. The mean duration of HIV infection and mean CD+ T-cell count of the study population were 71.08 ± 37 months and 522.17 ± 260.33 cells/µL, respectively. We found a high level of agreement in the quantification variables obtained using [18F]FDG PET and [68Ga]Ga-pentixafor PET. There is a good level of agreement in the arterial tracer quantification variables obtained using [18F]FDG PET/CT and [68Ga]Ga-pentixafor PET/CT in PLHIV. This suggests that [68Ga]Ga-pentixafor may be applied in the place of [18F]FDG PET/CT for the quantification of arterial inflammation.

FDG PET/CT for evaluating systemic arterial inflammation induced by anthracycline-based chemotherapy of Hodgkin lymphoma: A retrospective cohort study

To evaluate arterial fluorodeoxyglucose (FDG) uptake as a marker of arterial inflammation in multiple vascular beds in patients treated with anthracycline-based chemotherapy for Hodgkin lymphoma (HL).We used maximum standardized uptake value (SUVmax) and target-to-background ratio (TBR) to quantify arterial FDG uptake in the carotid artery, ascending aorta, abdominal aorta, and femoral artery obtained on positron emission tomography/computed tomography (PET/CT) imaging performed at baseline before chemotherapy and after completion of chemotherapy in patients with HL treated with an anthracycline-containing regimen. We compared the SUVmax and TBR obtained at baseline with that obtained post-chemotherapy for each arterial bed to evaluate the effect of anthracycline-based chemotherapy. We evaluated the effect of cardiovascular risk factors such as human immunodeficiency virus (HIV) infection, smoking, hypertension, and diabetes on the changes in SUVmax and TBR seen in the different arterial beds after anthracycline-based chemotherapy.Fifty-two patients were included with a mean age of 34.56 ± 10.19 years. There were 33 males, and 18 patients were HIV-infected. The mean interval between completion of chemotherapy and follow-up flourine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan was 65 weeks. We found no significant difference in arterial FDG uptake measured by SUVmax and TBR in all arterial beds between the pre- and post-chemotherapy FDG PET/CT. There was no significant impact of HIV infection, smoking, and hypertension on the changes in arterial FDG uptake following treatment with anthracycline-based chemotherapy.In patients with HL who were treated with anthracycline-based chemotherapy, we found no significant increase in arterial inflammation measured by FDG PET/CT after an average follow-up period of about 65 weeks since completion of chemotherapy.

Comparison of MRI, [18F]FDG PET/CT, and 99mTc-UBI 29-41 scintigraphy for postoperative spondylodiscitis-a prospective multicenter study

Purpose

Postoperative infection still constitutes an important complication of spine surgery, and the optimal imaging modality for diagnosing postoperative spine infection has not yet been established. The aim of this prospective multicenter study was to assess the diagnostic performance of three imaging modalities in patients with suspected postoperative spine infection: MRI, [¹⁸F]FDG PET/CT, and SPECT/CT with ^99mTc-UBI 29-41.

Methods

Patients had to undergo at least 2 out of the 3 imaging modalities investigated. Sixty-three patients enrolled fulfilled such criteria and were included in the final analysis: 15 patients underwent all 3 imaging modalities, while 48 patients underwent at least 2 imaging modalities (MRI + PET/CT, MRI + SPECT/CT, or PET/CT + SPECT/CT). Final diagnosis of postoperative spinal infection was based either on biopsy or on follow-up for at least 6 months. The MRI, PET/CT, and SPECT/CT scans were read blindly by experts at designated core laboratories. Spine surgery included metallic implants in 46/63 patients (73%); postoperative spine infection was diagnosed in 30/63 patients (48%).

Results

Significant discriminants between infection and no infection included fever (P = 0.041), discharge at the wound site (P < 0.0001), and elevated CRP (P = 0.042). There was no difference in the frequency of infection between patients who underwent surgery involving spinal implants versus those who did not. The diagnostic performances of MRI and [¹⁸F]FDG PET/CT analyzed as independent groups were equivalent, with values of the area under the ROC curve equal to 0.78 (95% CI: 0.64–0.92) and 0.80 (95% CI: 0.64–0.98), respectively. SPECT/CT with ^99mTc-UBI 29-41 yielded either unacceptably low sensitivity (44%) or unacceptably low specificity (41%) when adopting more or less stringent interpretation criteria. The best diagnostic performance was observed when combining the results of MRI with those of [¹⁸F]FDG PET/CT, with an area under the ROC curve equal to 0.938 (95% CI: 0.80–1.00).

Conclusion

[¹⁸F]FDG PET/CT and MRI both possess equally satisfactory diagnostic performance in patients with suspected postoperative spine infection, the best diagnostic performance being obtained by combining MRI with [¹⁸F]FDG PET/CT. The diagnostic performance of SPECT/CT with ^99mTc-UBI 29-41 was suboptimal in the postoperative clinical setting explored with the present study.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-020-05109-x.

18F-FDG PET/CT imaging of vulva cancer recurrence: A comparison of PET-derived metabolic parameters between women with and without HIV infection

Objective To assess the patterns of recurrence of vulva cancer on 18F-FDG PET/CT and to compare the 18F-FDG PET metabolic metrics in patients with and without Human Immunodeficiency Virus (HIV).

Methods Maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic tumour volume (MTV and total lesion glycolysis (TLG) were obtained on Flourine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F-FDG PET/CT) images of women referred with suspected or confirmed vulva cancer recurrence. We compared HIV-infected and HIV-uninfected patients regarding pattern disease recurrence, age at diagnosis, and the PET-derived metabolic indices.

Results We analyzed 33 patients with a mean age 50.76 ± 15.78 including 21 HIV-infected women. The majority of patients (94 %) had squamous cell carcinoma and 84.85 % were Blacks. Of the HIV-infected individuals, the median CD4 count was 526.0 cells/mm3 (IQR: 379.0–729.0). HIV infected patients were younger than the HIV uninfected at the time of diagnosis: 40.50 ± 8.87 vs 66.54 ± 9.71 respectively, p < 0.001. We found a local (vulvar) recurrence rate of 75.8 %. Nodal pelvic recurrences were higher in the HIV-infected patients than in the HIV uninfected patients (70 % vs 30 %, p = 0.027). Three patients had distant metastasis and all three were HIV-infected. There was a higher whole-body MTV and TLG among HIV-infected women compared with HIV-uninfected women, 103.39 vs 17.58 and 852.64 vs 101.79, respectively (p < 0.05 for both).

Conclusion HIV-infected women are diagnosed with vulva cancer at a younger age. HIV-infected patients had a higher rate of pelvic lymph node recurrence. There is a higher tumor burden at vulva cancer recurrence among women with HIV infection.

Underutilisation of nuclear medicine scans at a regional hospital in Nigeria: need for implementation research

Background

Nuclear medicine needs better integration into the Nigerian health system. To understand the relevant public health initiatives that will be required, this study assessed the pattern of nuclear medicine imaging services at the first nuclear medicine centre in Nigeria from January 2010 to December 2018.

Methods

The data of consecutive nuclear medicine (NM) scans performed between 1st January 2010 and 31st December 2018 at the NM department in a tertiary hospital in Nigeria were extracted from patient records and analysed using SAS version 9.4 (SAS Institute, Cary, NC). The National Cancer Institute’s Joinpoint software and QCIS (QGIS project) were used to estimate imaging trends and geographical spread of patients.

Results

An average of 486 scans per year was performed during the study period. Patients travelled from 32 of Nigeria’s 36 states, and the majority (65%) travelled more than 100 km to obtain NM scans. Bone scans accounted for 88.1% of the studies. The remainder were renal scintigraphy (7.3%), thyroid scans (2.5%), whole-body iodine scans (1.7%) and others (0.4%).

Conclusions

NM in Nigeria appears underutilised. Furthermore, the studies to characterise the access gaps and implementation needs will contribute to the design of practical strategies to strengthen NM services in Nigeria.

A prospective intra-individual comparison of [68Ga]Ga-PSMA-11 PET/CT, [68Ga]Ga-NODAGAZOL PET/CT, and [99mTc]Tc-MDP bone scintigraphy for radionuclide imaging of prostate cancer skeletal metastases

PURPOSE

Prostate cancer (PCa) commonly metastasizes to the bones. There are several radionuclide techniques for imaging PCa skeletal metastases. We aimed to compare the lesion detection rate of [⁶⁸Ga]Ga-PSMA-11 PET/CT, [⁶⁸Ga]Ga-NODAGA-zoledronate ([⁶⁸Ga]Ga-NODAGA^ZOL) PET/CT, and [^99mTc]Tc-MDP bone scan in the assessment of bone metastases in patients with advanced PCa.

METHODS

We prospectively recruited two cohorts of patients (staging and re-staging cohorts) with advanced prostate cancer. The staging cohort was treatment-naïve PCa patients who showed skeletal metastases on bone scan. These patients were subsequently imaged with [⁶⁸Ga]Ga-PSMA-11 PET/CT and [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT. Re-staging cohort was patients who were previously treated with PSMA-based radioligand therapy and were experiencing PSA progression. The re-staging cohort was imaged with [⁶⁸Ga]Ga-PSMA-11 PET/CT and [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT. We performed a per-patient and per-lesion analysis of skeletal metastases in both cohorts and made a comparison between scan findings.

RESULTS

Eighteen patients were included with a median age of 68 years (range = 48-80) and a median Gleason score of 8. There were ten patients in the staging cohort with a median PSA of 119.26 ng/mL (range = 4.63-18,948.00) and eight patients in the re-staging cohort with a median PSA of 48.56 ng/mL (range = 6.51-3175.00). In the staging cohort, skeletal metastases detected by [⁶⁸Ga]Ga-PSMA-11 PET/CT, [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT, and bone scan were 322, 288, and 261, respectively, p = 0.578. In the re-staging cohort, [⁶⁸Ga]Ga-PSMA-11 PET/CT and [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT detected 152 and 191 skeletal metastases, respectively, p = 0.529. In two patients with negative [⁶⁸Ga]Ga-PSMA-11 PET/CT findings, [⁶⁸Ga]Ga-NODAGA^ZOL detected one skeletal metastasis in one patient and 12 skeletal metastases in the other.

CONCLUSION

In patients with advanced prostate cancer, [⁶⁸Ga]Ga-PSMA-11 PET/CT may detect more lesions than [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT and [^99mTc]Tc-MDP bone scan for the staging of skeletal metastases. In patients who experience PSA progression on PSMA-based radioligand therapy, [⁶⁸Ga]Ga-NODAGA PET/CT is a more suitable imaging modality for the detection of skeletal lesions not expressing PSMA. In the setting of re-staging, [⁶⁸Ga]Ga-NODAGA^ZOL PET/CT may detect more lesions than [⁶⁸Ga]Ga-PSMA-11 PET/CT.

South African guidelines for receptor radioligand therapy (RLT) with Lu-177-PSMA in prostate cancer

BACKGROUND

Prostate cancer is an important cause of morbidity and mortality in South Africa, as it is in the rest of the world. In African men, however, prostate cancer tends to follow a more aggressive course when compared to their European counterparts. This is attributed to a plethora of diverse factors of which an underlying genetic component has been shown to be an important aspect. Such differences highlight the need for individualised therapy and for local guidelines. The aim of this guideline is to aid nuclear physicians and other clinicians who manage patients with prostate cancer in the correct identification and treatment of patients who are likely to benefit from receptor radioligand therapy.

RECOMMENDATIONS

There are a multitude of treatment modalities available for the treatment of prostate cancer and these therapies may be required at various time points during the course of the disease in any individual patient. A multidisciplinary approach is crucial in deciding which therapy, or combination of therapies, would be most advantageous at particular time points. The multidisciplinary team should include a urologist, oncologist and nuclear medicine physician as a minimum, and should ideally also involve a palliative/pain specialist, a dietician and a psychologist.

CONCLUSION

Treatment with ¹⁷⁷Lu-PSMA has emerged as a promising systemic modality, which involves the delivery of targeted radiation therapy in the form of β-particles to sites of tumour tissue. Therapy is provided on an outpatient basis, is well tolerated with relatively few side effects and has a positive effect on overall survival and quality of life. At present, it is used mostly in the setting of advanced, castrate-resistant cancer. Patients are selected (amongst other criteria) based on the prior PSMA-based SPECT/PET/CT imaging (⁹⁹mTc-,⁶⁸Ga- or ¹⁸F-PSMA), which should demonstrate sufficient receptor expression in order to consider PSMA-based targeted radionuclide therapy. Such imaging of an intended target prior to its therapeutic targeting is known as a theranostic approach.

68Ga-PSMA: a One-stop Shop in Radioactive Iodine Refractory Thyroid Cancer?

We report a case of a 47-year-old female known with metastatic papillary thyroid cancer. Her treatment history included total thyroidectomy and 3 previous radio ablations with a cumulative dose of 950 mCi of ¹³¹I. On follow-up, her thyroglobulin levels had demonstrated a rising trend (from 3789.0 to 4240.0 ug/L) despite a ¹²³I whole-body scan demonstrating a reduction in tracer avid lesions. She was suspected of having radio-resistant disease. The patient underwent both ¹⁸F-FDG and ⁶⁸Ga-PSMA PET/CT imaging with both scans demonstrating congruent lesions however with far greater intensity on the ⁶⁸Ga-PSMA study.

The Role of PET in Monitoring Therapy in Fungal Infections

Positron emission tomography (PET) is a powerful diagnostic nuclear medicine imaging technique. PET allows in vivo detection of a wide variety of physiologic and pathologic phenomena and it offers a noninvasive tool for the monitoring of therapy in various diseases. Invasive fungal infections (IFIs) are a global concern because of the increasing population of patients at risk of IFIs and the high morbidity and mortality. Therapy with antifungal agents is long-standing and expensive. The emerging resistant fungal strains make the management of IFIs challenging. There is an absolute need for a sensitive noninvasive biomarker capable of monitoring the disease activity of IFIs and determining the efficacy of treatment at an early time point. PET imaging with 18F-fluorodeoxyglucose (FDG) was used to detect and assess disease activity in IFI foci already over 20 years ago. At that time, it was suggested it could be a useful biomarker for monitoring antifungal therapy. However, this knowledge has still not been fully exploited for the management of IFIs. The literature reveals an increasing realization of the usefulness of PET in monitoring therapy of IFIs. In this review, we highlight the advantages of nuclear medicine techniques in the management of IFIs with emphasis of the role of PET in monitoring therapy efficacy.

Comparison of Fluorine(18)-fluorodeoxyglucose and Gallium(68)-citrate PET/CT in patients with tuberculosis

¹⁸F-FDG and ⁶⁸Ga-citrate PET/CT have both been shown to be useful in the management of tuberculosis (TB). We compared the abnormal PET findings of ¹⁸F-FDG- and ⁶⁸Ga-citrate-PET/CT in patients with TB.

METHODS

 Patients with TB on anti-TB therapy were included. Patients had a set of PET scans consisting of both ¹⁸F-FDG and ⁶⁸Ga-citrate. Abnormal lesions were identified, and the two sets of scans were compared. The scan findings were correlated to the clinical data as provided by the attending physician.

RESULTS

 46 PET/CT scans were performed in 18 patients, 11 (61 %) were female, and the mean age was 35.7 ± 13.5 years. Five patients also had both studies for follow-up reasons during the use of anti-TB therapy. Thirteen patients were co-infected with HIV. ¹⁸F-FDG detected more lesions than ⁶⁸Ga-citrate (261 vs. 166, p < 0.0001). ⁶⁸Ga-citrate showed a better definition of intracerebral lesions due to the absence of tracer uptake in the brain. The mean SUVmax was higher for ¹⁸F-FDG compared to ⁶⁸Ga-citrate (5.73 vs. 3.01, p < 0.0001). We found a significant correlation between the SUVmax of lesions that were determined by both tracers (r = 0.4968, p < 0.0001).

CONCLUSION

 Preliminary data shows ¹⁸F-FDG-PET detects more abnormal lesions in TB compared to ⁶⁸Ga-citrate. However, ⁶⁸Ga-citrate has better lesion definition in the brain and is therefore especially useful when intracranial TB is suspected.

18F-FDG PET/CT as a Noninvasive Biomarker for Assessing Adequacy of Treatment and Predicting Relapse in Patients Treated for Pulmonary Tuberculosis

Microbial culture is the gold standard for determining the effectiveness of tuberculosis treatment. End-of-treatment (EOT) ¹⁸F-FDG PET/CT findings are variable among patients with negative microbial culture results after completing a standard regimen of antituberculous treatment (ATT), with some patients having a complete metabolic response to treatment whereas others have residual metabolic activity (RMA). We herein determine the impact of findings on EOT ¹⁸F-FDG PET/CT on tuberculosis relapse in patients treated with a standard regimen of ATT for drug-sensitive pulmonary tuberculosis (DS-PTB). Methods: Patients who completed a standard regimen of ATT for DS-PTB and were declared cured based on a negative clinical and bacteriologic examination were prospectively recruited to undergo EOT ¹⁸F-FDG PET/CT. Images were assessed for the presence of RMA. Patients were subsequently followed up for 6 mo looking for symptoms of tuberculosis relapse. When new symptoms developed, relapse was confirmed with bacteriologic testing. Repeat ¹⁸F-FDG PET/CT was done in patients who relapsed. Results: Fifty-three patients were included (mean age, 37.81 ± 11.29 y), with 62% being male and 75% HIV-infected. RMA was demonstrated in 33 patients (RMA group), whereas 20 patients had a complete metabolic response to ATT (non-RMA group). There was a higher prevalence of lung cavitation in the RMA group (P = 0.035). The groups did not significantly differ in age, sex, presence of HIV infection, body mass index, or hemoglobin level (P > 0.05). On follow-up, no patients in the non-RMA group developed tuberculosis relapse. Three patients in the RMA group developed relapse. All patients who developed tuberculosis relapse had bilateral disease with lung cavitation. Conclusion: A negative EOT ¹⁸F-FDG PET/CT result is protective against tuberculosis relapse. Nine percent of patients with RMA after ATT may experience tuberculosis relapse within 6 mo of completing ATT. Bilateral disease with lung cavitation is prevalent among patients with tuberculosis relapse.

Arterial inflammation in young patients with human immunodeficiency virus infection: A cross-sectional study using F-18 FDG PET/CT

BACKGROUND

HIV infection is associated with the risk of development of atherosclerosis at a younger age. We compared arterial inflammation in HIV-infected and HIV-uninfected patients with otherwise low-risk factors for cardiovascular disease (CVD) using FDG PET/CT.

METHODS

242 patients aged 18-40 years with low-risk factors for CVD consisting of 121 HIV-infected patients and 121 HIV-uninfected age- and gender-matched controls were studied, mean age = 34.95 ± 5.46 years. We calculated and compared the target-to-background ratio of FDG uptake in ascending aorta of HIV-infected and non-infected patients.

RESULTS

Median CD4 count and viral load were 375.5 cells/mm3 (range 2-1094) and 6391.00 copies/mL (range 24-1,348,622), respectively. There was slightly higher but significant overlap in the TBR between HIV-infected group compared with control (1.22, 0.87-2.02 vs. 1.12, 0.38-1.40, P < 0.001). TBR was neither affected by CD4 count levels nor the presence or absence of detectable viremia. We also found no significant difference in TBR between male and female patients with HIV infection. We found a weak positive correlation between TBR and CD4 count, TBR and duration of HIV infection, and a very weak negative correlation between TBR and viral load. There was no significant difference in TBR between patients on HAART and those not yet commenced on therapy.

CONCLUSION

Marginally higher TBR with a significant overlap exist in HIV-infected patients compared with control. Arterial F-18 FDG uptake is not affected by the CD 4 count, viral load, gender, or duration of HIV infection.