Optimizing PSMA scintigraphy for resource limited settings - a retrospective comparative study.

BACKGROUND: PSMA PET/CT is the most sensitive molecular imaging modality for prostate cancer (PCa), yet much of the developing world has little or no access to PET/CT. [99mTc]Tc-PSMA scintigraphy (PS) is a cheaper and more accessible gamma camera-based alternative. However, many resource-constrained departments have only a single camera without tomographic or hybrid imaging functionality, and camera time is frequently in high demand. Simplifying imaging protocols by limiting the field of view (FOV) and omitting SPECT/CT or even SPECT may provide a partial solution. The aim was thus to determine the adequacy of PS planar-only and/or SPECT-only imaging protocols with a limited FOV. METHODS: The scans of 95 patients with histologically proven PCa who underwent PS with full-body planar and multi-FOV SPECT/CT were reviewed. The detection rates for uptake in the prostate gland/bed and in metastases were compared on planar, SPECT, and SPECT/CT. The agreement between modalities was calculated for the detection of metastases and for staging. The impact of imaging a limited FOV was determined. RESULTS: Pathological prostatic uptake was seen in all cases on SPECT/CT (excluding two post-prostatectomy patients), 90.3% of cases on SPECT, and 15.1% on planar images (p < 0.001). Eleven (11.7%) patients had seminal vesicle involvement on SPECT/CT, which was undetectable/indistinguishable on planar images and SPECT. The agreement between modalities was moderate to good (κ = 0.41 to 0.61) for the detection of nodal metastases, with detection rates that did not differ significantly (SPECT/CT = 11.6%, SPECT = 8.4%, planar = 5.3%). Detection rates for bone metastases were 14.7% (SPECT/CT) and 11.6% (SPECT and planar). Agreement between modalities for the detection of bone metastases was good (κ = 0.73 to 0.77). Three (3.1%) patients had visceral metastases on SPECT/CT, two of which were detected on SPECT and planar. There was good agreement between modalities for the TNM staging of patients (κ = 0.70 to 0.88). No metastatic lesions were missed on the limited FOV images. CONCLUSION: When PS scintigraphy is performed, SPECT/CT is recommended. However, the lack of SPECT/CT capabilities should not preclude the use of PS in the presence of limited resources, as both planar and SPECT imaging are adequate and will correctly stage most PCa patients. Furthermore, time-based optimisations are achievable by limiting the FOV to exclude the distal lower limbs.

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.

Differences in Tumour Aggressiveness Based on Molecular Subtype and Race Measured by [18F]FDG PET Metabolic Metrics in Patients with Invasive Carcinoma of the Breast.

Breast cancer in women of African descent tends to be more aggressive with poorer prognosis. This is irrespective of the molecular subtype. [18F]FDG PET/CT metrics correlate with breast cancer aggressiveness based on molecular subtype. This study investigated the differences in [18F]FDG PET/CT metrics of locally advanced invasive ductal carcinoma (IDC) among different racial groups and molecular subtypes. Qualitative and semiquantitative readings of [18F]FDG PET/CT acquired in women with locally advanced IDC were performed. Biodata including self-identified racial grouping and histopathological data of the primary breast cancer were retrieved. Statistical analysis for differences in SUVmax, MTV and TLG of the primary tumour and the presence of regional and distant metastases was conducted based on molecular subtype and race. The primary tumour SUVmax, MTV, TLG and the prevalence of distant metastases were significantly higher in Black patients compared with other races (p < 0.05). The primary tumour SUVmax and presence of distant metastases in the luminal subtype and the primary tumour SUVmax and TLG in the basal subtype were significantly higher in Black patients compared with other races (p < 0.05). The significantly higher PET parameters in Black patients with IDC in general and in those with luminal and basal carcinoma subtypes suggest a more aggressive disease phenotype in this race.

Short-Interval, Low-Dose [ 177 Lu]Lu-Prostate-Specific Membrane Antigen in the Treatment of Refractory Glioblastoma.

ABSTRACT: Prostate-specific membrane antigen (PSMA) is expressed on the neovasculature as well as to some extent on the glioblastoma cells. With this background, we report the case of a 34-year-old man with recurrent glioblastoma who was treated with 2 cycles of low-dose [ 177 Lu]Lu-PSMA after exhausting all available treatment options in the state sector. Baseline imaging demonstrated intense PSMA signal in the known lesion, which was amenable to therapy. The prospect of [ 177 Lu]Lu-PSMA-based therapy for glioblastoma is warranted going forward.

The Impact of PET/CT on Paediatric Oncology.

This review paper will discuss the use of positron emission tomography/computed tomography (PET/CT) in paediatric oncology. Functional imaging with PET/CT has proven useful to guide treatment by accurately staging disease and limiting unnecessary treatments by determining the metabolic response to treatment. 18F-Fluorodeoxyglucose (2-[18F]FDG) PET/CT is routinely used in patients with lymphoma. We highlight specific considerations in the paediatric population with lymphoma. The strengths and weaknesses for PET/CT tracers that compliment Meta-[123I]iodobenzylguanidine ([123I]mIBG) for the imaging of neuroblastoma are summarized. 2-[18F]FDG PET/CT has increasingly been used in the staging and evaluation of disease response in sarcomas. The current recommendations for the use of PET/CT in sarcomas are given and potential future developments and highlighted. 2-[18F]FDG PET/CT in combination with conventional imaging is currently the standard for disease evaluation in children with Langerhans-cell Histiocytosis (LCH) and the non-LCH disease spectrum. The common pitfalls of 2-[18F]FDG PET/CT in this setting are discussed.

SARS-CoV-2 vaccination site as possible pitfall on somatostatin receptor imaging.

SARS-CoV-2 (COVID-19) vaccination numbers are globally increasing. Therefore, an increased chance exists that patients undergoing Peptide Receptor Radionuclide Therapy (PRRT) or diagnostic radionuclide imaging for Neuroendocrine Tumours (NETs) may have recently received vaccination. We report the imaging findings of two NETs patients, A-following [177Lu] Lu-DOTATATE PRRT post therapy planar scintigraphy and single photon emission computed tomography with computed tomography (SPECT/CT), and B-following [68 Ga]Ga-DOTA-NOC positron emission tomography with computed tomography (PET/CT) respectively. Both studies were done few days after COVID-19 vaccination. Patient A showed a new focus of uptake in the left deltoid muscle; and Patient B showed uptake in the left deltoid and a left axillary lymph node. Nuclear Physicians need to be aware of pitfalls with somatostatin receptor radionuclide imaging post-vaccination to ensure accurate interpretation, as well as dosimetric considerations with vaccine-related post-therapy uptake.

Tuberculosis: Role of Nuclear Medicine and Molecular Imaging With Potential Impact of Neutrophil-Specific Tracers.

With Tuberculosis (TB) affecting millions of people worldwide, novel imaging modalities and tools, particularly nuclear medicine and molecular imaging, have grown with greater interest to assess the biology of the tuberculous granuloma and evolution thereof. Much early work has been performed at the pre-clinical level using gamma single photon emission computed tomography (SPECT) agents exploiting certain characteristics of Mycobacterium tuberculosis (MTb). Both antituberculous SPECT and positron emission tomography (PET) agents have been utilised to characterise MTb. Other PET tracers have been utilised to help to characterise the biology of MTb (including Gallium-68-labelled radiopharmaceuticals). Of all the tracers, 2-[18F]FDG has been studied extensively over the last two decades in many aspects of the treatment paradigm of TB: at diagnosis, staging, response assessment, restaging, and in potentially predicting the outcome of patients with latent TB infection. Its lower specificity in being able to distinguish different inflammatory cell types in the granuloma has garnered interest in reviewing more specific agents that can portend prognostic implications in the management of MTb. With the neutrophil being a cell type that portends this poorer prognosis, imaging this cell type may be able to answer more accurately questions relating to the tuberculous granuloma transmissivity and may help in characterising patients who may be at risk of developing active TB. The formyl peptide receptor 1(FPR1) expressed by neutrophils is a key marker in this process and is a potential target to characterise these areas. The pre-clinical work regarding the role of radiolabelled N-cinnamoyl -F-(D) L - F - (D) -L F (cFLFLF) (which is an antagonist for FPR1) using Technetium 99m-labelled conjugates and more recently radiolabelled with Gallium-68 and Copper 64 is discussed. It is the hope that further work with this tracer may accelerate its potential to be utilised in responding to many of the current diagnostic dilemmas and challenges in TB management, thereby making the tracer a translatable option in routine clinical care.

The need for nationally accepted guidelines for undergraduate nuclear medicine teaching in MBChB programmes in South Africa.

According to the South African Health Professions Act No. 56 of 1974, specific skills outcomes of MBChB programmes are that a medical graduate must be able to utilise diagnostic aids, interpret findings and make diagnoses. Imaging techniques are an integral part of the numerous diagnostic and therapeutic aids used in contemporary medical practice; however, in South Africa, no formal directives exist to guide programme directors or nuclear medicine departments regarding an appropriate undergraduate nuclear medicine educational module. As of 2013, six South African schools of medicine are involved in undergraduate nuclear medicine teaching, in which it forms part of clinical modules taught at varying stages in the academic curriculum. Against this backdrop is the inequitable distribution of nuclear medicine resources, training facilities and staffing in the local state health sector. Inadequate undergraduate teaching and provincial differences in nuclear medicine service provision suggest that many clinicians and graduating medical students are unaware of how radionuclide techniques can facilitate patient management. This high level of imaging illiteracy has been associated with lack of patient referral, poor quality and inadequate referral, poor knowledge of radiation doses and poor awareness of radiation risks. Here we highlight the challenges of undergraduate nuclear medicine teaching in South Africa, emphasising the need for the implementation of guidelines for undergraduate nuclear medicine education. Employing nationally accepted guidelines for undergraduate nuclear medicine teaching in South African MBChB programmes will contribute to the effective utilisation of nuclear medicine and molecular imaging as a diagnostic and therapeutic modality by newly qualified medical practitioners.

Renal cortical transit time as a predictor for pyeloplasty in pediatric patients with unilateral hydronephrosis.

Majority of patients with unilateral hydronephrosis (HN) detected on ultrasound do not require pyeloplasty. The measurement of the cortical transit time (CTT) has been demonstrated by several authors to predict the need for patients who may require pyeloplasty. The study aimed to assess if CTT would have predicted a drop in differential renal function (DRF) in patients with unilateral HN on the affected side and to assess whether CTT would differ on the first renogram between those patients who had a pyeloplasty and those who did not have a pyeloplasty. Sixty-eight patients with at least two renograms with unilateral HN with a normal contralateral kidney were observed retrospectively. The CTT was recorded for each kidney. Renograms were processed three times to measure the DRF. The mean of the three DRF measurements was used for analysis. The mean CTT of the left and right hydronephrotic kidneys was 6.0 min and 6.7 min, respectively. The relationship between CTT and DRF as well as CTT and anterior posterior diameter in the first renogram of those patients who did not have a pyeloplasty was statistically significant (P < 0.05). In the 20 patients who had a pyeloplasty, there was a drop of more than 10% in the DRF of three patients. No significant difference was found in CTT or DRF when comparing the group who had surgery against the group who did not have surgery. The current study was unable to demonstrate in our series of patients that CTT can predict a drop in DRF in those patients who would require pyeloplasty.