Metabolic Tumor Volume on 18-Fluorodeoxyglucose Positron Emission Tomography as a Prognostic Marker of Survival in Patients With Locally Advanced or Metastatic Neuroendocrine Neoplasms Treated With 177Lutetium-DOTA-Octreotate Peptide Receptor Radionuclide Therapy.

OBJECTIVE: We investigated metabolic tumor volume (MTV) and total lesion glycolysis (TLG) on pre-treatment FDG-PET as prognostic markers for survival in patients with metastatic neuroendocrine neoplasms (NENs) receiving peptide receptor radionuclide therapy (PRRT). METHODS: A retrospective review of patients with metastatic NENs receiving PRRT was undertaken. Pre-treatment FDG-PET images were analyzed and variables collected included MTV and TLG (dichotomized by median into high vs low). Main Outcomes were overall survival (OS) and progression-free survival (PFS) by MTV and TLG (high vs low). RESULTS: One hundred five patients were included. Median age was 64 years (50% male). Main primary NEN sites were small bowel (43.8%) and pancreas (40.0%). Median MTV was 3.8 mL and median TLG was 19.9. Dichotomization formed identical cohorts regardless of whether MTV or TLG were used. Median OS was 72 months; OS did not differ based on MTV/TLG high versus low (47.4 months vs not reached; hazard ratio, 0.43; 95% confidence interval [CI], 0.18-1.04; P = 0.0594). Median PFS was 30.4 months; PFS differed based on MTV/TLG high versus low (21.6 months vs 45.7 months; hazard ratio, 0.35; 95% CI, 0.19-0.64; P = 0.007). CONCLUSIONS: Low MTV/TLG on pre-treatment FDG-PET was associated with longer PFS in metastatic NEN patients receiving PRRT.

[18F]FDG PET/CT-Avid Discordant Volume as a Biomarker in Patients with Gastroenteropancreatic Neuroendocrine Neoplasms: A Multicenter Study.

[18F]FDG PET/CT and [68Ga]Ga-DOTATATE PET/CT are both used to predict tumor biology in neuroendocrine neoplasms. Although the presence of discordant ([18F]FDG-avid/non-[68Ga]Ga-DOTATATE-avid) disease predicts poor prognosis, the significance of the volume of such discordant disease remains undetermined. The aim of this study is to investigate discordant tumor volume as a potential biomarker in patients with advanced gastroenteropancreatic neuroendocrine neoplasms (GEPNENs). Methods: A multicenter retrospective study in patients with advanced GEPNENs and paired [18F]FDG and [68Ga]Ga-DOTATATE PET/CT no more than 85 d apart was conducted. Patients with discordant disease were identified by the NETPET score, and discordant lesions were contoured with a flat [18F]FDG SUV cutoff of 4. The primary variable of interest was the total discordant volume (TDV), which was the sum of the volumes of discordant lesions. Patients were dichotomized into high- and low-TDV cohorts by the median value. The primary endpoint was overall survival. Results: In total, 44 patients were included (50% men; median age, 60 y), with primary cancers in the pancreas (45%), small bowel (23%), colon (20%), and other (12%). Of the patients, 5% had grade 1 disease, 48% had grade 2 disease, and 48% had grade 3 disease (24% well differentiated, 67% poorly differentiated, 10% unknown within the grade 3 cohort). The overall median survival was 14.1 mo. Overall survival was longer in the low-TDV cohort than in the high-TDV cohort (median volume, 43.7 cm3; survival time, 23.8 mo vs. 9.4 mo; hazard ratio, 0.466 [95% CI, 0.229-0.948]; P = 0.0221). Patients with no more than 2 discordant intrahepatic lesions survived longer than those with 2 or more lesions (31.8 mo vs. 10.2 mo, respectively; hazard ratio, 0.389 [95% CI, 0.194-0.779]; P = 0.0049). Conclusion: TDV is a potential prognostic biomarker in GEPNENs and should be investigated in future neuroendocrine neoplasm trials.

[18F]-fluoroethyl-L-tyrosine (FET) in glioblastoma (FIG) TROG 18.06 study: protocol for a prospective, multicentre PET/CT trial.

INTRODUCTION: Glioblastoma is the most common aggressive primary central nervous system cancer in adults characterised by uniformly poor survival. Despite maximal safe resection and postoperative radiotherapy with concurrent and adjuvant temozolomide-based chemotherapy, tumours inevitably recur. Imaging with O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) has the potential to impact adjuvant radiotherapy (RT) planning, distinguish between treatment-induced pseudoprogression versus tumour progression as well as prognostication. METHODS AND ANALYSIS: The FET-PET in Glioblastoma (FIG) study is a prospective, multicentre, non-randomised, phase II study across 10 Australian sites and will enrol up to 210 adults aged ≥18 years with newly diagnosed glioblastoma. FET-PET will be performed at up to three time points: (1) following initial surgery and prior to commencement of chemoradiation (FET-PET1); (2) 4 weeks following concurrent chemoradiation (FET-PET2); and (3) within 14 days of suspected clinical and/or radiological progression on MRI (performed at the time of clinical suspicion of tumour recurrence) (FET-PET3). The co-primary outcomes are: (1) to investigate how FET-PET versus standard MRI impacts RT volume delineation and (2) to determine the accuracy and management impact of FET-PET in distinguishing pseudoprogression from true tumour progression. The secondary outcomes are: (1) to investigate the relationships between FET-PET parameters (including dynamic uptake, tumour to background ratio, metabolic tumour volume) and progression-free survival and overall survival; (2) to assess the change in blood and tissue biomarkers determined by serum assay when comparing FET-PET data acquired prior to chemoradiation with other prognostic markers, looking at the relationships of FET-PET versus MRI-determined site/s of progressive disease post chemotherapy treatment with MRI and FET-PET imaging; and (3) to estimate the health economic impact of incorporating FET-PET into glioblastoma management and in the assessment of post-treatment pseudoprogression or recurrence/true progression. Exploratory outcomes include the correlation of multimodal imaging, blood and tumour biomarker analyses with patterns of failure and survival. ETHICS AND DISSEMINATION: The study protocol V.2.0 dated 20 November 2020 has been approved by a lead Human Research Ethics Committee (Austin Health, Victoria). Other clinical sites will provide oversight through local governance processes, including obtaining informed consent from suitable participants. The study will be conducted in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice. Results of the FIG study (TROG 18.06) will be disseminated via relevant scientific and consumer forums and peer-reviewed publications. TRIAL REGISTRATION NUMBER: ANZCTR ACTRN12619001735145.

64Cu Treatment Planning and 67Cu Therapy with Radiolabeled [64Cu/67Cu]MeCOSar-Octreotate in Subjects with Unresectable Multifocal Meningioma: Initial Results for Human Imaging, Safety, Biodistribution, and Radiation Dosimetry.

Our aim was to report the use of 64Cu and 67Cu as a theranostic pair of radionuclides in human subjects. An additional aim was to measure whole-organ dosimetry of 64Cu and 67Cu attached to the somatostatin analog octreotate using the sarcophagine MeCOSar chelator (SARTATE) in subjects with somatostatin receptor-expressing lesions confined to the cranium, thereby permitting normal-organ dosimetry for the remainder of the body. Methods: Pretreatment PET imaging studies were performed up to 24 h after injection of [64Cu]Cu-SARTATE, and normal-organ dosimetry was estimated using OLINDA/EXM. Subsequently, the trial subjects with multifocal meningiomas were given therapeutic doses of [67Cu]Cu-SARTATE and imaged over several days using SPECT/CT. Results: Five subjects were initially recruited and imaged using PET/CT before treatment. Three of the subjects were subsequently administered 4 cycles each of [67Cu]Cu-SARTATE followed by multiple SPECT/CT imaging time points. No serious adverse events were observed, and no adverse events led to withdrawal from the study or discontinuation from treatment. The estimated mean effective dose was 3.95 × 10-2 mSv/MBq for [64Cu]Cu-SARTATE and 7.62 × 10-2 mSv/MBq for [67Cu]Cu-SARTATE. The highest estimated organ dose was in spleen, followed by kidneys, liver, adrenals, and small intestine. The matched pairing was shown by PET and SPECT intrasubject imaging to have nearly identical targeting to tumors for guiding therapy, demonstrating a potentially accurate and precise theranostic product. Conclusion: 64Cu and 67Cu show great promise as a theranostic pair of radionuclides. Further clinical studies will be required to examine the therapeutic dose required for [67Cu]Cu-SARTATE for various indications. In addition, the ability to use predictive 64Cu-based dosimetry for treatment planning with 67Cu should be further explored.

Dual [68Ga]DOTATATE and [18F]FDG PET/CT in patients with metastatic gastroenteropancreatic neuroendocrine neoplasms: a multicentre validation of the NETPET score.

BACKGROUND: Gastroenteropancreatic neuroendocrine neoplasms (GEPNENs) are heterogeneous in clinical course, biology, and outcomes. The NETPET score predicts survival by scoring uptake on dual [68Ga]DOTATATE and [18F]FDG PET/CT scans. We aimed to validate previous single-centre findings in a multicentre, international study. METHODS: Dual scans were assigned a NETPET score of P1 (DOTATATE positive/FDG negative), P2-4 (DOTATATE positive/FDG positive), or P5 (DOTATATE negative/FDG positive). NETPET score, histological grade, age at diagnosis, and presence/absence of extrahepatic disease were compared to overall survival/time to progression on univariate and multivariate analysis. RESULTS: 319 metastatic/unresectable GEPNEN patients were included. The NETPET score was significantly associated with overall survival and time to progression on univariate and multivariate analysis (all p < 0.01). Median overall survival/time to progression was 101.8/25.5 months for P1, 46.5/16.7 months for P2-4, and 11.5/6.6 months for P5. Histological grade correlated with overall survival and time to progression on univariate and multivariate analysis (all p < 0.01), while presence/absence of extrahepatic disease did not. Age at diagnosis correlated with overall survival on univariate and multivariate analysis (p < 0.01). The NETPET score also correlated with histological grade (p < 0.001). CONCLUSION: This study validates the NETPET score as a prognostic biomarker in metastatic GEPNENs, capturing the complexity of dual PET imaging.

The MANGO study: a prospective investigation of oxygen enhanced and blood-oxygen level dependent MRI as imaging biomarkers of hypoxia in glioblastoma.

Background: Glioblastoma (GBM) is the most aggressive type of brain cancer, with a 5-year survival rate of ~5% and most tumours recurring locally within months of first-line treatment. Hypoxia is associated with worse clinical outcomes in GBM, as it leads to localized resistance to radiotherapy and subsequent tumour recurrence. Current standard of care treatment does not account for tumour hypoxia, due to the challenges of mapping tumour hypoxia in routine clinical practice. In this clinical study, we aim to investigate the role of oxygen enhanced (OE) and blood-oxygen level dependent (BOLD) MRI as non-invasive imaging biomarkers of hypoxia in GBM, and to evaluate their potential role in dose-painting radiotherapy planning and treatment response assessment. Methods: The primary endpoint is to evaluate the quantitative and spatial correlation between OE and BOLD MRI measurements and [18F]MISO values of uptake in the tumour. The secondary endpoints are to evaluate the repeatability of MRI biomarkers of hypoxia in a test-retest study, to estimate the potential clinical benefits of using MRI biomarkers of hypoxia to guide dose-painting radiotherapy, and to evaluate the ability of MRI biomarkers of hypoxia to assess treatment response. Twenty newly diagnosed GBM patients will be enrolled in this study. Patients will undergo standard of care treatment while receiving additional OE/BOLD MRI and [18F]MISO PET scans at several timepoints during treatment. The ability of OE/BOLD MRI to map hypoxic tumour regions will be evaluated by assessing spatial and quantitative correlations with areas of hypoxic tumour identified via [18F]MISO PET imaging. Discussion: MANGO (Magnetic resonance imaging of hypoxia for radiation treatment guidance in glioblastoma multiforme) is a diagnostic/prognostic study investigating the role of imaging biomarkers of hypoxia in GBM management. The study will generate a large amount of longitudinal multimodal MRI and PET imaging data that could be used to unveil dynamic changes in tumour physiology that currently limit treatment efficacy, thereby providing a means to develop more effective and personalised treatments.

Towards personalised dosimetry in patients with liver malignancy treated with 90Y-SIRT using in vivo-driven radiobiological parameters.

BACKGROUND: The prediction of response is one of the major challenges in radiation-based therapies. Although the selection of accurate linear-quadratic model parameters is essential for the estimation of radiation response and treatment outcome, there is a limited knowledge about these radiobiological parameters for liver tumours using radionuclide treatments. METHODS: The "clinical radiobiological" parameters ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) for twenty-five patients were derived using the generalised linear-quadratic model, the diagnostic ([18F] FDG PET/CT) and therapeutic ([90Y]-SIR-Spheres PET/CT) images to compute the biological effective dose and tumour control probability (TCP) for each patient. RESULTS: It was estimated that the values for [Formula: see text] and [Formula: see text] parameters range in ≈ 0.001-1 Gy-1 and ≈ 1-49 Gy, respectively. We have demonstrated that the time factors, [Formula: see text], [Formula: see text] and [Formula: see text] are the key parameters when evaluating liver malignancy lesional response to [90Y]SIR-Spheres treatment. Patients with cholangiocarcinoma have been shown to have the longest average [Formula: see text] (≈ 236 ± 67 d), highest TCP (≈ 53 ± 17%) and total liver lesion glycolysis response ([Formula: see text] ≈ 64%), while patients with metastatic colorectal cancer tumours have the shortest average [Formula: see text] (≈ 129 ± 19 d), lowest TCP (≈ 28 ± 13%) and [Formula: see text] ≈ 8%, respectively. CONCLUSIONS: Tumours with shorter [Formula: see text] have shown a shorter [Formula: see text] and thus poorer TCP and [Formula: see text]. Therefore, these results suggest for such tumours the [90Y]SIR-Spheres will be only effective at higher initial dose rate (e.g. > 50 Gy/day).

AN UNUSUAL CAUSE OF GAMMA CAMERA CONTAMINATION.

This report is of an unusual case of radioactive contamination of a gamma camera after scanning two individuals who had been treated 3 days prior with ablative doses of radioiodine (131I) for thyroid cancer. A combination of observed half-life and pulse-height spectroscopy were employed to identify the radio-contaminant. The source of the contamination was eventually found to be a single human hair, presumably contaminated by the individual sucking her hair while waiting for the scan to start. This case demonstrates that hair can be contaminated by saliva and potentially other bodily fluids in the post-ablation setting and that using physical characteristics, in this case the observed half-life and pulse-height spectroscopy, can be useful in identifying the radio-contaminant.

The Importance of Training, Accreditation, and Guidelines for the Practice of Theranostics: The Australian Perspective.

In nuclear medicine, theranostics is a burgeoning development that is rapidly being implemented worldwide. There is an increasing need to provide a multidisciplinary framework to the practice of theranostics, ensuring that patients receive this treatment safely and are secure in the knowledge that their health-care practitioners are adequately trained. Nuclear medicine experts in Australia have taken the initiative of producing a set of theranostic guidelines relevant to Australian medical practice. These guidelines encompass specialist qualifications, patient care, radiopharmaceutical production, radiation safety, and dosimetry. We propose adaptation of these guidelines by other countries, and we promote standards of practice leading to optimal clinical outcomes for patients receiving theranostic treatments.

Computed tomography (CT)-defined sarcopenia and myosteatosis are prevalent in patients with neuroendocrine neoplasms (NENs) treated with peptide receptor radionuclide therapy (PRRT).

BACKGROUND/OBJECTIVES: Neuroendocrine neoplasms (NEN) may predispose patients to malnutrition. CT-defined sarcopenia and myosteatosis are common in other tumour types and recognized adverse prognostic factors. However, the prevalence and prognostic impact of sarcopenia and myosteatosis remain undetermined in NEN patients to date. METHODS: A retrospective study of NEN patients treated with peptide receptor radionuclide therapy (PRRT) at a tertiary institution from 2012 to 2017. Patients with PET/CT imaging at baseline and follow-up were included. The L3 slice of the co-localizing CT was analysed using the Alberta Protocol. Skeletal muscle cross-sectional area and muscle attenuation were measured and compared with pre-defined cut-offs. The primary endpoint was the prevalence of sarcopenia and myosteatosis according to previously published cut-offs. RESULTS: Fourty-nine patients (median age 64 (range 26-80) years) were included. The most common primary sites of tumour were the small bowel (51%) and pancreas (26%). Baseline sarcopenia was prevalent in 67% of patients and myosteatosis in 71%. Forty-five percent of patients gained weight over the course of PRRT. The presence of baseline sarcopenia was not associated with progression-free survival (20.8 mo vs. 20.7 mo, HR 0.86, p = 0.70) nor overall survival. Similarly, baseline myosteatosis (PFS 19.5 mo vs. 20.8 mo, HR 0.77, p = 0.47) was not significantly associated with survival outcomes. The mean (SD) age of those with myosteatosis was 60.8 ± 11.6 years compared to 49.7 ± 12.7 years for those without (p = 0.003). CONCLUSIONS: Body composition analysis is feasible using routinely acquired PET/CT data for patients with NEN. CT-defined sarcopenia and myosteatosis are prevalent in NEN patients, although myosteatosis is more common with increasing age. These findings were not associated with worsened overall or progression-free survival in the current study.

Individualised dosimetry and safety of SIRT for intrahepatic cholangiocarcinoma.

BACKGROUND: The aim of this study was to investigate the safety and efficacy of selective internal radiation therapy (SIRT) with 90Y resin microspheres for the treatment of Intrahepatic Cholangiocarcinoma (ICC). A total of 23 SIRT procedures from 18 ICC subjects were analysed to determine a lesion-based dose/response relationship with absorbed dose measures from 90Y PET and metabolic response as measured on [18F]FDG PET. Average absorbed dose (Davg), minimum dose to 70% of the volume (D70), volume receiving at least 50 Gy (V50), biological effective dose (BED) and equivalent uniform dose (EUD), were compared to changes in metabolic volume, maximum standardised uptake value (SUVmax) and total lesion glycolysis (TLG). Dose to normal liver was assessed with changes in liver uptake rate as measured with [99mTc]mebrofenin scintigraphy for a cohort of 20 subjects with primary liver malignancy (12 ICC, 8 hepatocellular carcinoma (HCC)). RESULTS: Thirty-four lesions were included in the analysis. A relationship was found between metabolic response and both Davg and EUD similar to that seen previously in metastatic colorectal cancer (mCRC), albeit trending towards a lower response plateau. Both dose and SUV coefficient of variation within the lesion (CoVdose and CoVSUV), baseline TLG and EUD were found to be mildly significant predictors of response. No strong correlation was seen between normal liver dose and change in [99mTc]mebrofenin liver uptake rate; low baseline uptake rate was not indicative of declining function following SIRT, and no subjects dropped into the 'poor liver function' category. CONCLUSIONS: ICC lesions follow a similar dose-response trend as mCRC, however, despite high lesion doses a full metabolic response was rarely seen. The CoV of lesion dose may have a significant bearing on response, and EUD correlated more tightly with metabolic response compared to Davg. SIRT in primary liver malignancy appears safe in terms of not inducing a clinically significant decline in liver function, and poor baseline uptake rate is not predictive of a reduction in function post SIRT.

Safety and tolerability of Miltuximab® - a first in human study in patients with advanced solid cancers.

OBJECTIVES: Miltuximab® is a chimeric antibody targeting Glypican-1 (GPC-1), a cell surface antigen which is overexpressed in solid cancers. Miltuximab® has shown promising safety and efficacy in radioimmunotherapy models of prostate cancer. This first in human study used Miltuximab® radiolabelled with Gallium-67 ([67Ga]Ga-DOTA-Miltuximab®). The primary study endpoint was to establish safety and tolerability of Miltuximab®. Secondary endpoints were biodistribution, tumour targeting and pharmacokinetic analysis. METHODS: Four cohorts of three patients (9 with advanced prostate cancer, 2 with pancreatic and 1 with bladder cancer) were dosed with 1 mg, ~250 MBq of [67Ga]Ga-DOTA-Miltuximab®. Cohort 1 received [67Ga]Ga-DOTA-Miltuximab® alone, while cohorts 2-4 were pre-infused with increasing doses (3.5, 11.5 and 24 mg, respectively) of unlabelled Miltuximab®-DOTA 1 hour prior to [67Ga]Ga-DOTA-Miltuximab®. Safety and tolerability were assessed by clinical and standard laboratory assessments. Patients underwent whole body gamma-camera scans and SPECT/CT scans up to 144 h post-infusion. Total organ radiation exposure was determined by dosimetry of whole-body gamma scans. RESULTS: The dosing regimen was well tolerated, with no drug-related adverse events observed. Liver and spleen uptake of [67Ga]Ga-DOTA-Miltuximab® was observed. Liver uptake was reduced by pre-infusion of unlabelled Miltuximab®-DOTA. Dosimetry analysis showed a favorable exposure profile. [67Ga]Ga-DOTA-Miltuximab® targeting to tumour sites was observed in two prostate cancer patients who had failed enzalutamide treatment. Higher doses of unlabelled antibody achieved lower liver uptake and increased antibody serum half life. CONCLUSIONS: This study is the first in human for Miltuximab® a first in class antibody targeting GPC-1. The trial met its primary endpoint of safety, demonstrating its potential as a safe and tolerable monoclonal antibody. This safety data, together with targeting to tumour lesions and biodistribution information supports the further clinical development of Miltuximab® as a theranostic agent in a planned Phase I human trial.

Dual PET Imaging in Bronchial Neuroendocrine Neoplasms: The NETPET Score as a Prognostic Biomarker.

PET scans using 18F-FDG and somatostatin receptor imaging agents are both used in imaging of neuroendocrine neoplasms (NENs). We have suggested the "NETPET score," using uptake of both PET tracers, as a prognostic biomarker in NENs. The name NETPET score was suggested previously to capture the score's intent to summarize information from dual PET imaging in neuroendocrine tumors. We previously demonstrated the effectiveness of the NETPET score in gastroenteropancreatic NENs (GEPNENs). Its prognostic relevance in bronchial NENs remains undetermined. Methods: This is a retrospective multicenter study (2011-2018) assessing patients who had advanced bronchial NEN and who underwent both 18F-FDG and 68Ga-DOTATATE PET within 60 d of each other. The NETPET score was assigned by experienced nuclear medicine physicians and compared with other clinical data such as World Health Organization grade. The primary outcome was overall survival; NETPET score and other prognostic variables were analyzed using univariate and multivariate analyses by the Cox proportional-hazards model. Results: Thirty-eight patients were included for review. The NETPET score and histology were significantly correlated with overall survival in univariate analyses (P = 0.003, P = 0.01). On multivariate analysis, only the NETPET score remained significant (P = 0.03). The NETPET score was significantly associated with histologic grade (P = 0.006, χ2 test). Conclusion: The NETPET score is a prognostic biomarker in bronchial NENs as well as GEPNENs. Although it needs to be validated in prospective studies, it holds significant promise as a biomarker for a wide range of NENs.

Overlooked potential of positrons in cancer therapy.

Positron (ß+) emitting radionuclides have been used for positron emission tomography (PET) imaging in diagnostic medicine since its development in the 1950s. Development of a fluorinated glucose analog, fluorodeoxyglucose, labelled with a ß+ emitter fluorine-18 (18F-FDG), made it possible to image cellular targets with high glycolytic metabolism. These targets include cancer cells based on increased aerobic metabolism due to the Warburg effect, and thus, 18F-FDG is a staple in nuclear medicine clinics globally. However, due to its attention in the diagnostic setting, the therapeutic potential of ß+ emitters have been overlooked in cancer medicine. Here we show the first in vitro evidence of ß+ emitter cytotoxicity on prostate cancer cell line LNCaP C4-2B when treated with 20 Gy of 18F. Monte Carlo simulation revealed thermalized positrons (sub-keV) traversing DNA can be lethal due to highly localized energy deposition during the thermalization and annihilation processes. The computed single and double strand breakages were ~ 55% and 117% respectively, when compared to electrons at 400 eV. Our in vitro and in silico data imply an unexplored therapeutic potential for ß+ emitters. These results may also have implications for emerging cancer theranostic strategies, where ß+ emitting radionuclides could be utilized as a therapeutic as well as a diagnostic agent once the challenges in radiation safety and protection after patient administration of a radioactive compound are overcome.

RetroSPECT: Gallium-67 as a Long-Lived Imaging Agent for Theranostics.

A limitation to the wider introduction of personalised dosimetry in theranostics is the relative paucity of imaging radionuclides with suitable physical and chemical properties to be paired with a long-lived therapeutic partner. As most of the beta-emitting therapeutic radionuclides emit gamma radiation as well they could potentially be used as the imaging radionuclide as well as the therapeutic radionuclide. However, the downsides are that the beta radiation will deliver a significant radiation dose as part of the treatment planning procedure, and the gamma radiation branching ratio is often quite low. Gallium-67 has been in use in nuclear medicine for over 50 years. However, the tremendous interest in gallium imaging in theranostics in recent times has focused on the PET radionuclide gallium-68. In this article it is suggested that the longer-lived gallium-67, which has desirable characteristics for imaging with the gamma camera and a suitably long half-life to match biological timescales for drug uptake and turnover, has been overlooked, in particular, for treatment planning with radionuclide therapy. Gallium-67 could also allow non-PET facilities to participate in theranostic imaging prior to treatment or for monitoring response after therapy. Gallium-67 could play a niche role in the future development of personalised medicine with theranostics.

Quantitative PET in the 2020s: a roadmap.

Positron emission tomography (PET) plays an increasingly important role in research and clinical applications, catalysed by remarkable technical advances and a growing appreciation of the need for reliable, sensitive biomarkers of human function in health and disease. Over the last 30 years, a large amount of the physics and engineering effort in PET has been motivated by the dominant clinical application during that period, oncology. This has led to important developments such as PET/CT, whole-body PET, 3D PET, accelerated statistical image reconstruction, and time-of-flight PET. Despite impressive improvements in image quality as a result of these advances, the emphasis on static, semi-quantitative 'hot spot' imaging for oncologic applications has meant that the capability of PET to quantify biologically relevant parameters based on tracer kinetics has not been fully exploited. More recent advances, such as PET/MR and total-body PET, have opened up the ability to address a vast range of new research questions, from which a future expansion of applications and radiotracers appears highly likely. Many of these new applications and tracers will, at least initially, require quantitative analyses that more fully exploit the exquisite sensitivity of PET and the tracer principle on which it is based. It is also expected that they will require more sophisticated quantitative analysis methods than those that are currently available. At the same time, artificial intelligence is revolutionizing data analysis and impacting the relationship between the statistical quality of the acquired data and the information we can extract from the data. In this roadmap, leaders of the key sub-disciplines of the field identify the challenges and opportunities to be addressed over the next ten years that will enable PET to realise its full quantitative potential, initially in research laboratories and, ultimately, in clinical practice.

Australian experience of peptide receptor radionuclide therapy in lung neuroendocrine tumours.

BACKGROUND: Peptide receptor radionuclide therapy (PRRT) is an approved treatment modality for gastroenteropancreatic neuroendocrine tumours (GEP NETs), Although Phase III randomised clinical trial data is not available for NETs of other site of origin, in practice, PRRT is used more widely in clinical practice, based on its mechanism of targeting the somatostatin receptor. Use of PRRT for lung (bronchial) NET, specifically typical and atypical carcinoid (TC, AC), has been reported only in small retrospective case series. This multicentre study adds to the evidence regarding utility of PRRT for lung NETs. MATERIALS AND METHODS: A retrospective chart review of patients with TC and AC who received 177Lu-dotatate PRRT between January 2002 and June 2019 in six hospitals across Australia was undertaken. Data regarding demographics, efficacy and toxicity was evaluated at each site by the treating clinician. RESULTS: Forty-eight patients (32 AC, 15 TC, 1 unclassified) received a median of four 177Lu-dotatate treatments. There was a median of one prior line of systemic treatment (range: 0-3). The response rate to 177Lu-dotatate was 33%, with a median overall survival of 49 months (range of 3-91), at a median follow up of 33 months. This compares favourably with GEP NET. Overall toxicity was recorded as modest. CONCLUSIONS: 177Lu-dotatate PRRT in patients with lung NETs is used in real world practice, where it appears well-tolerated with some efficacy. Further evidence could be obtained through a global prospective clinical or registry trial.

Routine Early 68Ga-DOTATATE Positron Emission Tomography Has Low Yield After Resection of Appendiceal Neuroendocrine Neoplasms.

OBJECTIVES: Appendiceal neuroendocrine neoplasms (appNEN) generally carry a low recurrence risk. Ga-DOTATATE positron emission tomography (DOTA PET) is increasingly used as it is more sensitive than cross-sectional imaging. We hypothesize that early DOTA PET is unlikely to detect recurrent disease in patients with low-risk resected appNEN because of the delayed pattern of recurrence. METHODS: Retrospective study (dual review) of patients undergoing DOTA PET 0 to 18 months after resected appNEN. The primary outcome was the proportion of scans demonstrating residual disease. RESULTS: Forty-one patients were included (median age, 29 years; 63% female), most with small, low-grade appNEN. No scans (0%) showed residual/distant disease. Eight (20%) of 41 scans showed indeterminate findings requiring follow-up. Five (12%) scans were recommended for follow-up with modalities other than DOTA PET (vertebra, 3; thyroid; bone, 1 each). Three (7%) were recommended for follow-up with DOTA PET (all with indeterminate abdominal uptake). These 3 patients had no recurrent disease on follow-up. CONCLUSIONS: The Ga-DOTATATE PET is of no value when performed in the first 18 months after resected appNEN. Although 20% of scans showed indeterminate findings, more than half did not require repeat DOTA PET. Despite advantages over cross-sectional imaging, DOTA PET is not recommended in staging after completely resected appNEN.