[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.

A practical method for assessing quantitative scanner accuracy with long-lived radionuclides: The ARTnet insert

Objectives

To address the problem of using large volumes of long-lived radionuclides in test phantoms to check calibration accuracy of PET and SPECT systems we have developed a test object which (a) contains less radioactivity, (b) has a low total volume, and (c) is easier to store than currently used phantoms, while still making use of readily-available "standardised" test objects.

Methods

We have designed a hollow acrylic cylindrical insert compatible with the NEMA/IEC PET Body Image Quality (IQ) phantom used in NU 2 performance testing of PET systems. The insert measures 90 mm internal diameter and 70 mm internal height and so is sufficiently large to not be subject to partial volume effects in PET or SPECT imaging. The volume of the insert is approximately 500 mL. It has been designed as a replacement for the standard long cylindrical "lung insert" in the IQ phantom without needing to remove the fillable hollow spheres of the phantom. The insert been tested with 18F, 68Ga and 124I PET/CT and 99mTc, 131I and 177Lu SPECT/CT on scanners that had previously been calibrated for these radionuclides.

Results

The scanners were found to produce accurate image reconstructions in the insert with  5% of the true value without any confounding uncertainty from partial volume effects when compared to NEMA NU 2-2018 Phantom measurement.

Conclusions

The "ARTnet Insert" is simple to use, inexpensive, compatible with current phantoms and is suitable for both PET and SPECT systems. It does not suffer from significant partial volume losses permitting its use even with the poor spatial resolution of high-energy imaging with 131I SPECT. Furthermore, it uses less radioactivity in a smaller volume than would be required to fill the entire phantom as is usually done. Long-term storage is practical while allowing radioactive decay of the insert contents.

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.

[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.

Single-centre experience with peptide receptor radionuclide therapy for neuroendocrine tumours (NETs): results using a theranostic molecular imaging-guided approach

AIM

To summarise our centre's experience managing patients with neuroendocrine tumours (NETs) in the first 5 years after the introduction of peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-octreotate (LUTATE). The report emphasises aspects of the patient management related to functional imaging and use of radionuclide therapy.

METHODS

We describe the criteria for treatment with LUTATE at our centre, the methodology for patient selection, and the results of an audit of clinical measures, imaging results and patient-reported outcomes. Subjects are treated initially with four cycles of ~ 8 GBq of LUTATE administered as an outpatient every 8 weeks.

RESULTS

In the first 5 years offering LUTATE, we treated 143 individuals with a variety of NETs of which approx. 70% were gastroentero-pancreatic in origin (small bowel: 42%, pancreas: 28%). Males and females were equally represented. Mean age at first treatment with LUTATE was 61 ± 13 years with range 28-87 years. The radiation dose to the organs considered most at risk, the kidneys, averaged 10.6 ± 4.0 Gy in total. Median overall survival (OS) from first receiving LUTATE was 72.5 months with a median progression-free survival (PFS) of 32.3 months. No evidence of renal toxicity was seen. The major long-term complication seen was myelodysplastic syndrome (MDS) with a 5% incidence.

CONCLUSIONS

LUTATE treatment for NETs is a safe and effective treatment. Our approach relies heavily on functional and morphological imaging informing the multidisciplinary team of NET specialists to guide appropriate therapy, which we suggest has contributed to the favourable outcomes seen.

V/Q SPECT and SPECT/CT in Pulmonary Embolism

Ventilation and perfusion (V/Q) lung scintigraphy has been used in the assessment of patients with suspected pulmonary embolism for more than 50 y. Advances in imaging technology make SPECT and SPECT/CT feasible. This article will examine the application and technical considerations associated with performing 3-dimensional V/Q SPECT and the contribution of a coacquired CT scan. The literature tends to be mixed and contradictory in terms of appropriate investigation algorithms for pulmonary embolism. V/Q SPECT and SPECT/CT offer significant advantages over planar V/Q, with or without the advantages of Technegas ventilation, and if available should be the preferred option in the evaluation of patients with suspected pulmonary embolism.

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.

Partial volume effect in SPECT & PET imaging and impact on radionuclide dosimetry estimates

Objectives

The spatial resolution of emission tomographic imaging systems can lead to a significant underestimation in the apparent radioactivity concentration in objects of size comparable to the resolution volume of the system. The aim of this study was to investigate the impact of the partial volume effect (PVE) on clinical imaging in PET and SPECT with current state-of-the-art instrumentation and the implications that this has for radionuclide dosimetry estimates.

Methods

Using the IEC Image Quality Phantom we have measured the underestimation in observed uptake in objects of various sizes for both PET and SPECT imaging conditions. Both single pixel measures (i.e., SUV_max) and region of interest mean values were examined over a range of object sizes. We have further examined the impact of the PVE on dosimetry estimates in OLINDA in ¹⁷⁷Lu SPECT imaging based on a subject with multiple somatostatin receptor positive paragangliomas in the head and neck.

Results

In PET, single pixel estimates of uptake are affected for objects less than approximately 18 mm in minor axis with existing systems. In SPECT imaging with medium energy collimators (e.g., for ¹⁷⁷Lu imaging), however, the underestimates are far greater, where single pixel estimates in objects less than 2-3×the resolution volume are significantly impacted. In SPECT, region of interest mean values are underestimated in objects less than 10 cm in diameter. In the clinical case example, the dosimetry measured with SPECT ranged from more than 60% underestimate in the largest lesion (28×22 mm in maximal cross-section; 10.2 cc volume) to >99% underestimate in the smallest lesion (4×5 mm; 0.06 cc).

Conclusion

The partial volume effect remains a significant factor when estimating radionuclide uptake in vivo, especially in small volumes. Accurate estimates of absorbed dose from radionuclide therapy will be particularly challenging until robust solutions to correct for the PVE are found.

64Cu Treatment Planning and67Cu Therapy with Radiolabelled SARTATE ([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.

Practical learning through radiation physics problem solving

INTRODUCTION

The identification of unknown radionuclides is an authentic practical activity for students that provides the foundations for clinical problem solving, especially in the storage and management of radioactive waste. As different radionuclides have different half-lives, some of which are quite long, the storage of waste material has to accommodate the longest of these. Cross contamination requires a method of identifying the radionuclide samples in a mixed sample to safely and appropriately manage disposal. Similarly, identifying a single unknown sample of a radionuclide allows correct handling and disposal.

METHODS

Performing a systematic investigation of the physical properties of unknown radioactive samples is a rich learning opportunity to instil understanding of important physics principles among students in nuclear medicine.

RESULTS

This manuscript outlines an investigation developed that would allow students to identify single unknown radionuclides based on physical properties and identify the constituent radionuclides of a mixed sample using some additional mathematical curve stripping.

CONCLUSION

The processes and solutions are provided with real data and this practical activity can be replicated by students generating their own data.

IMPLICATIONS FOR PRACTICE

This paper provides a template and analysis/interpretation guideline for educators and clinicians to deepen understanding of foundation physics. Enhanced and deeper understanding are a vehicle for improved problem solving in clinical and research practice.

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.

Australasian Gastrointestinal Trials Group (AGITG) CONTROL NET Study: 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) and capecitabine plus temozolomide (CAPTEM) for pancreas and midgut neuroendocrine tumours (pNETS, mNETS)—Final results

4122

Background: CAPTEM is an accepted regimen for patients (pts) with advanced pNETs. Single agent PRRT is now a standard of care for progressive WHO Grade 1/2 mNETs. High activity was seen with PRRT/CAPTEM in a single arm Phase I/II trial. This study aims to determine the activity of combining CAPTEM with PRRT in mNETs and pNETs pts. Methods: Non-comparative randomised open label parallel group phase II trial with 2:1 randomisation to PRRT/CAPTEM (experimental arm) vs. PRRT (mNETs control) and CAPTEM (pNETS control). PRRT/CAPTEM: 7.8GBq 177Lu Octreotate (Lutate) given intravenously (IV) on day 10 every 8 weeks for 4 cycles, with concurrent oral capecitabine 750mg/m2 b.i.d. days 1-14 and temozolomide 75mg/m2 b.i.d. days 10-14 every 56 day cycle, up to 4 cycles. PRRT alone: 7.8GBq 177Lu Octreotate (Lutate) given intravenously (IV) on day 1 every 8 weeks for 4 cycles. CAPTEM alone: Oral capecitabine 750mg/m2 b.i.d. days 1-14 and days 29-42; Oral temozolomide 75mg/m2 b.i.d. days 10-14 and 38-42 every 56 day (8w) cycle. Primary endpoint: Progression free survival (PFS). mNETS: At 15 months, assuming PFS 66.4% in control arm; target PFS ³ 80%; pNETS: At 12 months, assuming PFS 60% in control arm; target PFS ³ 75%. Secondary endpoints: Objective tumor response rate (complete or partial) (OTRR), overall survival (OS), adverse events (AEs). Results: 75 pts enrolled (Dec 2015 – Nov 2018): mNETs 33 PRRT/CAPTEM, 14 PRRT, median follow up (mFU) 60.3 months; pNETS 19 PRRT/CAPTEM, 9 CAPTEM, mFU 57.5 months (mo). Late Grade 3/4 haematologic AEs: mNETS: 2/32 (6%) PRRT/CAPTEM pts and 4/13 (31%) PRRT pts. Events included myelodysplastic syndrome (40 mo), leukaemia (60 mo), pancytopenia (50 mo), anaemia (32 mo), thrombocytopenia (7 mo). No late haematologic G3/4 AEs were reported in the pNETS cohort. No late renal toxicity was identified in all study arms. Conclusions: CONTROL NETs is the first randomized trial to demonstrate efficacy for PRRT in pNETs, in addition to a standard of care. Extended follow up confirms durable CAPTEM/PRRT activity, with superior PFS in pNETs. Late haematologic toxicity was seen in both mNET PRRT arms but was not higher with additional CAPTEM. The activity of CAPTEM/PRRT in pNETs should be tested in the phase III setting. Clinical trial information: ACTRN12615000909527. [Table: see text]

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

Theranostics is a burgeoning development in nuclear medicine which is being rapidly implemented worldwide. There is an increasing need to provide a multidisciplinary framework to the practice of theranostics, to ensure that patients receive this treatment in a safe manner and are provided with security in the knowledge that the health practitioners providing the service are adequately trained. Nuclear medicine experts in Australia have taken the initiative to produce 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 these guidelines could be adapted for other countries, and promote standards of practice leading to optimal clinical outcomes for patients receiving theranostic treatments.

NIMG-49. A PROSPECTIVE, MULTI-CENTRE TRIAL OF FET-PET IN GLIOBLASTOMA PATIENTS - THE TROG 18.06 FIG STUDY: KEY ASPECTS OF IMAGING AND RADIATION ONCOLOGY CREDENTIALING

The FIG study is a prospective non-randomised study now recruiting up to 210 newly diagnosed GBM participants across ten Australian sites. Study outcomes will address the role of [18F] fluoroethyl-L-tyrosine positron emission tomography (FET-PET) in radiotherapy (RT) planning, evaluation of post-treatment changes versus disease progression and prognostication. We describe here the methodology and preliminary outcomes for site credentialing. Eligible participants with GBM undergo FET-PET imaging at three time-points: FET-PET1-post-operative pre-chemo-RT, FET-PET2 acquired one month post-chemo-RT and FET-PET3 (+/-FDG-PET) triggered when clinical and/or radiological (MRI) progression is suspected. Dynamic and static FET-PET images are analysed qualitatively and quantitatively. Radiotherapy is as per standard care with the treating Radiation Oncologist (RO) blinded to FET-PET1. Site nuclear medicine (NM) physicians are required to delineate a biological target volume (BTV) based on FET-PET1 with hybrid RT volumes derived post-hoc. Pre-trial NM quality assurance comprises certification from the Australasian Radiopharmaceutical Trials Network encompassing FET-PET radiochemistry Quality Control and PET camera calibration. Site and central integrated workflows incorporating multi-modality image registration, target volume/region of interest contouring and analysis have been developed. NM benchmarking involves delineation of FET-PET BTVs in 3 cases with another 3 cases addressing response criteria interpretation harmonized across FET-PET, FDG-PET and MRI. Site ROs complete 3 cases involving standard and hybrid target volume delineation based on pre-derived FET-PET volumes. All NM and RO credentialing cases undergo central expert review. To date, of six sites which have submitted full credentialing data, 19/21 RO and 6/6 planning cases were passed. Of 72 NM cases, 18/72 (25%) required resubmission, primarily related to ensuring standardisation of background regions and time activity curve interpretation. The FIG study will be pivotal in establishing the role of FET-PET in GBM management. The robust NM and RO credentialing program will build capacity and expertise in FET-PET production, acquisition and image interpretation.

A Technical Overview of Technegas as a Lung Ventilation Agent

Technegas is a carbon-based nanoparticle developed in Australia in 1984 and has been in widespread clinical use, including SPECT imaging, since 1986. Although ^81mKr offers the ideal ventilation properties of a true gas, Technegas is considered preferred in more than 60 countries for ventilation imaging yet has limited adoption in the United States. In March 2020, a new U.S. Food and Drug Administration application was lodged for Technegas, and the impending approval warrants a detailed discussion of the technical aspects of the technology for those for whom it is new. Technegas is a simple yet versatile system for producing high-quality ^99mTc-based ventilation studies. The design affords safety to patients and staff, including consideration of radiation and biologic risks. Technegas is the gold standard for the ventilation portion of SPECT-based ventilation-perfusion studies in pulmonary embolism and several respiratory pathologies. When approved by the U.S. Food and Drug Administration, Technegas will extend advantages to workflow, safety, and study quality for departments that adopt the technology.

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 (D_avg), 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 (SUV_max) 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 D_avg 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 (CoV_dose and CoV_SUV), 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 D_avg. 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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00406-2.

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.

Effect of combination inhaled therapy on ventilation distribution measured by SPECT/CT imaging in uncontrolled asthma

Asthma is characterized by heterogeneous ventilation as measured by three-dimensional ventilation imaging. Combination inhaled corticosteroid/long-acting β₂-agonist (ICS/LABA) treatment response is variable in asthma, and effects on regional ventilation are unknown. Our aims were to determine whether regional ventilation defects decrease after ICS/LABA treatment and whether small airways dysfunction predicts response in uncontrolled asthma. Twenty-two symptomatic participants with asthma underwent single-photon emission computed tomography (SPECT)/CT imaging with Technegas, before and after 8-wk fluticasone/formoterol (1,000/40 µg/day) treatment. Lung regions that were nonventilated, low ventilated, or well ventilated were calculated using an adaptive threshold method and were expressed as a percentage of total lung volume. Multiple-breath nitrogen washout (MBNW) was used to measure diffusion-dependent and convection-dependent small airways function (Sacin and Scond, respectively). Forced oscillation technique (FOT) was used to measure respiratory system resistance and reactance. At baseline and posttreatment, Scond z-score was related to percentage of nonventilated lung, whereas Sacin z-score was related to percentage of low-ventilated lung. Although symptoms, spirometry, FOT, and MBNW improved following treatment, there was no mean change in ventilation measured by SPECT. There was, however, a wide range of changes in SPECT ventilation such that greater percentage of nonventilated lung, older age, and higher Scond predicted a reduction in nonventilated lung after treatment. SPECT ventilation defects are overall unresponsive to ICS/LABA, but the response is variable, with improvement occurring when small airways dysfunction and ventilation defects are more severe. Persistent ventilation defects that correlate with Scond suggest that mechanisms such as non-ICS responsive inflammation or remodeling underlie these defects.NEW & NOTEWORTHY This study provides insights into the mechanisms of high-dose ICS treatment in uncontrolled asthma. Ventilation defects as measured by SPECT/CT imaging respond heterogeneously to increased ICS/LABA treatment, with improvement occurring when ventilation defects and impairment of convection-dependent small airways function are more severe. Persistent correlations between ventilation defects and measures of small airways function suggest the potential presence of ICS nonresponsive inflammation and/or remodeling.

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.

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.

Theranostic SPECT reconstruction for improved resolution: application to radionuclide therapy dosimetry

Background

SPECT-derived dose estimates in tissues of diameter less than 3× system resolution are subject to significant losses due to the limited spatial resolution of the gamma camera. Incorporating resolution modelling (RM) into the SPECT reconstruction has been proposed as a possible solution; however, the images produced are prone to noise amplification and Gibbs artefacts. We propose a novel approach to SPECT reconstruction in a theranostic setting, which we term SPECTRE (single photon emission computed theranostic reconstruction); using a diagnostic PET image, with its superior resolution, to guide the SPECT reconstruction of the therapeutic equivalent. This report demonstrates a proof in principle of this approach.

Methods

We have employed the hybrid kernelised expectation maximisation (HKEM) algorithm implemented in STIR, with the aim of producing SPECT images with PET-equivalent resolution. We demonstrate its application in both a dual ⁶⁸Ga/¹⁷⁷Lu IEC phantom study and a clinical example using ⁶⁴Cu/⁶⁷Cu.

Results

SPECTRE is shown to produce images comparable in accuracy and recovery to PET with minimal introduction of artefacts and amplification of noise.

Conclusion

The SPECTRE approach to image reconstruction shows improved quantitative accuracy with a reduction in noise amplification. SPECTRE shows great promise as a method of improving SPECT radioactivity concentrations, directly leading to more accurate dosimetry estimates in small structures and target lesions. Further investigation and optimisation of the algorithm parameters is needed before this reconstruction method can be utilised in a clinical setting.

Overlooked potential of positrons in cancer therapy

Positron (β⁺) 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 β⁺ 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 β⁺ emitters have been overlooked in cancer medicine. Here we show the first in vitro evidence of β⁺ 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 β⁺ emitters. These results may also have implications for emerging cancer theranostic strategies, where β⁺ 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.

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.

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.

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.

Australasian Gastrointestinal Trials Group (AGITG) CONTROL NET Study: Phase II study evaluating the activity of 177Lu-Octreotate peptide receptor radionuclide therapy (LuTate PRRT) and capecitabine, temozolomide CAPTEM)—First results for pancreas and updated midgut neuroendocrine tumors (pNETS, mNETS)

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Background: CAPTEM is an accepted regimen for patients (pts) with advanced pNETs. Single agent 177Lu-Octreotate PRRT is now a standard of care for progressive WHO Grade (G) 1/2 mNETs. High activity was seen with LuTate/CAPTEM in a single arm Phase I/II trial. This study was undertaken to determine the relative activity of adding CAPTEM to LuTate PRRT in pts with mNETs and pNETs. Methods: Non-comparative randomised open label parallel group phase II trial with 2:1 randomisation to PRRT/CAPTEM (experimental arm) vs. PRRT (mNETs control) and CAPTEM (pNETS control). PRRT/CAPTEM: 7.8GBq LuTate day(D) 10, 8 weekly (wkly) x 4, with b.i.d. oral CAP 750mg/m2 D1-14 & TEM 75mg/m2D10-14, 8 wkly x 4; PRRT: 8 wkly x 4; CAPTEM 8 wkly x 4. Primary endpoint: Progression free survival (PFS). mNETS- at 15 months (mo) assuming 15mo PFS 66.4% in control arm, aiming for PFS ³ 80%; pNETS- at 12mo assuming 12mo PFS 60% in control arm, aiming for PFS ³ 75%. Secondary endpoints: Objective tumour response rate (complete or partial) (OTRR), clinical benefit rate (OTRR, stable disease) (CBR), toxicity, quality of life. Results: 75 pts enrolled (Dec 2015 – Nov 2018): mNETs 33 PRRT/CAPTEM and 14 PRRT; pNETS 19 PRRT/CAPTEM and 9 CAPTEM. mNETS: Median follow-up 35mo; 15mo PFS was 90% (95% CI: 73-97%) v 92% (95% CI: 57-99%); OTRR 31% vs 15%; and CBR 97% vs 92% for PRRT/CAPTEM v PRRT respectively. Treatment related adverse events (AEs): 24/32 PRRT/CAPTEM pts had at least one G3 event (75%) vs 5/13 (38%, PRRT); and 4/32 pts at least one G4 event (13%) v 1/13 (8%) respectively, mostly haematologic (haem). Only one patient failed to complete therapy (PRRT/CAPTEM). pNETS: Median follow-up 34mo; 12mo PFS was 76% (95% CI: 48-90%) v 67% (95% CI: 28-88%); OTRR 68% vs 33%; and CBR 100% vs 100% for PRRT/CAPTEM v CAPTEM respectively. Treatment related AEs: 5/18 PRRT/CAPTEM pts had at least one G3 event (28%) vs 3/9 (33%) CAPTEM; 3/18 pts at least one G4 event (17%) v 1/9 (11%) respectively. Conclusions: CAPTEM/PRRT is active, meeting its target landmark PFS for CAPTEM/PRRT (12mo pNETs; 15mo mNETs) with numerically greater OTRR in both pNETs and mNETs, but with more haem toxicity in mNETs. As activity was high in both control arms longer follow up is required to determine if the relative activity of PRRT/CAPTEM is sufficient to warrant Phase III evaluation. Clinical trial information: ACTRN12615000909527 .

First results for Australasian Gastrointestinal Trials Group (AGITG) control net study: Phase II study of 177Lu-octreotate peptide receptor radionuclide therapy (LuTate PRRT) +/- capecitabine, temozolomide (CAPTEM) for midgut neuroendocrine tumors (mNETs)

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Background: Single agent 177Lu-octreotate peptide receptor radionuclide therapy is now a standard of care for progressive mNETS. High activity was seen with LuTate and concurrent CAPTEM chemotherapy in a single arm Phase I/II trial. This study was undertaken to determine the relative activity of adding CAPTEM to LuTate PRRT in patients with mNETs. Methods: Non-comparative randomised open label phase II trial of PRRT +/- CAPTEM in patients with mNETs, with 2:1 randomisation: PRRT /CAPTEM (experimental arm) vs. PRRT (control). PRRT /CAPTEM: 7.8GBq LuTate day(D) 10, 8 weekly (wkly) x 4, with b.i.d. oral CAP 750mg/m2 D1-14 & TEM 75mg/m2 D10-14, 8 wkly x 4, vs. PRRT 8 wkly x 4. Primary endpoint: progression free survival (PFS) at 15 months assuming 15 month PFS of 66.4% in the control arm, aiming for PFS rate > 80%; secondary endpoints: objective tumour response rate (complete or partial response) (OTRR), clinical benefit rate (complete or partial response, stable disease) (CBR), toxicity, and QOL. Results: 47 patients enrolled (Dec 2015 - Feb 2018): 33 PRRT/CAPTEM and 14 PRRT. Two patients withdrew prior to treatment. Patient characteristics were balanced except gender (female 58% vs. 14%). Two patients received 2 prior systemic regimens. After a median follow-up of 32 months, the 15 month PFS was 90% (95% CI: 73-97%) v 92% (95% CI: 57-99%); OTRR 25% vs 15%; and CBR 97% vs 92% for PRRT/CAPTEM v PRRT respectively. For treatment related adverse events 22/32 CAPTEM patients experienced one Grade 3 event (69%) vs 5/13 (38%, PRRT); 4/32 pts experienced one Grade 4 event (13%) v 1/13 (8%) respectively. Only one patient failed to complete therapy due to toxicity (PRRT/CAPTEM). Conclusions: This initial planned analysis demonstrates similarly high 15 month PFS for CAPTEM/PRRT relative to PRRT alone. OTRR is numerically higher but at the cost of greater toxicity. Longer follow up is required to determine if the activity of PRRT/CAPTEM is sufficient to warrant Phase III evaluation. Clinical trial information: ACTRN12615000909527.

High Metabolic Tumour Volume on 18-Fluorodeoxyglucose Positron Emission Tomography Predicts Poor Survival from Neuroendocrine Neoplasms

INTRODUCTION

18-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) avidity in neuroendocrine neoplasms (NENs) has been associated with higher-grade disease. 18F-FDG avidity and high SUVmax have been demonstrated to predict poor outcome. Quantitative metrics of 18F-FDG PET, specifically metabolic tumour volume (MTV) and total lesion glycolysis (TLG), have been shown to be prognostic factors in other malignancies, but these have not been investigated to date in NENs.

METHODS

Patients with NEN undergoing 18F-FDG at Royal North Shore Hospital from 2012 to 2018 were included. Images were analysed with automated segmentation (SUV cut-off of 4) followed by contour verification by a nuclear medicine physician and manual segmentation where required. Variables collected included patient age, histological grade, MTV, TLG, and SUVmax/SUVmean. The primary outcome was overall survival (OS), and the secondary outcome was progression-free survival (PFS). Univariate (UV) and multivariate (MV) analyses were performed for OS and PFS for MTV and TLG separately. For UV analysis, the median MTV and TLG were used to dichotomise the cohort. MTV/TLG for NENs of different histological grade were compared using ANOVA.

RESULTS

One hundred and ninety patients were included (median age 63.5, 49% female). Primary site: 42% small bowel, 32% pancreas, 15% other gastrointestinal, 6% lung, 6% other. Grade for gastroenteropancreatic NENs and bronchial NEN: G1/typical carcinoid 37%, G2/atypical carcinoid 40%, G3/large-cell/small-cell neuroendocrine carcinoma 16%, unknown 8%. Median MTV was 4.83 mL (range 0-3,161 mL) and median TLG was 29.22. Patients with high MTV had worse median OS compared to those with low MTV (29.7 months vs. not reached, HR 4.1, 95% CI 2.25-7.49, p < 0.00001). Considered as a continuous variable, MTV predicted for poorer OS on UV (p < 0.00001) and MV (p = 0.003) analyses. Whilst histological grade was significant on both UV and MV, SUVmax was significant on UV (p < 0.00001) but not MV (p = 0.76). Tumours of higher grade had higher MTV (mean MTV - G1: 39.6 mL, G2: 107 mL, G3: 337 mL; p = 0.0001 by ANOVA).

CONCLUSIONS

Quantitative analysis of 18F-FDG PET in NEN is feasible. High MTV/TLG are predictors of poor prognosis in NEN. Further analyses are underway to investigate a larger cohort of NEN patients.

Follow-up Recommendations for Completely Resected Gastroenteropancreatic Neuroendocrine Tumors

There is no consensus on optimal follow-up for completely resected gastroenteropancreatic neuroendocrine tumors. Published guidelines for follow-up are complex and emphasize closer surveillance in the first 3 years after resection. Neuroendocrine tumors have a different pattern and timescale of recurrence, and thus require more practical and tailored follow-up. The Commonwealth Neuroendocrine Tumour Collaboration convened an international multidisciplinary expert panel, in collaboration with the North American Neuroendocrine Tumor Society, to create patient-centered follow-up recommendations for completely resected gastroenteropancreatic neuroendocrine tumors. This panel used the RAND/UCLA (University of California, Los Angeles) Appropriateness Method to generate recommendations. A large international survey was conducted outlining current the surveillance practice of neuroendocrine tumor practitioners and shortcomings of the current guidelines. A systematic review of available data to date was supplemented by recurrence data from 2 large patient series. The resultant guidelines suggest follow-up for at least 10 years for fully resected small-bowel and pancreatic neuroendocrine tumors and also identify clinical situations in which no follow-up is required. These recommendations stratify follow-up strategies based on evidence-based prognostic factors that allow for a more individualized patient-centered approach to this complex and heterogeneous malignant neoplasm.

A Brief History of Lung Ventilation and Perfusion Imaging Over the 50-Year Tenure of the Editors of Seminars in Nuclear Medicine

The ventilation/perfusion lung scan has been in continuous use for approximately half a century, the same lifetime as Seminars in Nuclear Medicine. Remarkably, the founding Editors-in-Chief have continued to guide the journal over this entire period. In this Feschrift issue celebrating their enormous contribution, we review the history of the lung scan, its highs and lows, the transition from planar to SPECT/CT V/Q scans, and the future that is in store in this age of multimodality functional imaging. We concur with the published view of one of the retiring editors (LMF) that V/Q scintigraphy is indeed alive and well and has a definite future in clinical medicine.

Outcomes of the miltuximab first in human trial and proposed study design for a phase I trial 89Zr/177Lu theranostic trial

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Background: Miltuximab is a chimeric antibody targeting Glypican-1 which is overexpressed in prostate cancer. Miltuximab has shown promising safety and efficacy in radioimmunotherapy models of prostate cancer. Methods: Metastatic patients (prostate, pancreatic and bladder) were dosed with unlabelled Miltuximabfollowed by the infusion of 1 mg/250MBq 67Ga-Miltuximab. Patients underwent whole body gamma and SPECT/CT scans up to 144 hours post-infusion. Standard of care imaging was performed at least 14 days before and after participation. Safety was evaluated by an external monitoring committee. Total organ exposure was determined by dosimetry of whole-body gamma scans. Antibody pharmacokinetics were also determined. Results: 12 patients were enrolled into the trial. Miltuximabwas well tolerated and did not elicit any drug-related adverse reactions. Liver and spleen uptake of 67Ga-Miltuximabwas observed from 30 min to 72 hours post dose. Pre-infusion of unlabelled Miltuximab resulted in reduced liver accumulation and increased distribution in the rest of the body. Miltuximab targeting to sites of active progressive disease was observed in certain prostate cancer patients who had failed enzalutamide treatment. Dosimetry analysis combined with antibody pharmacokinetic data was used to establish safe dose limits for a Phase 1 study. Conclusions: This study is the first in human for Miltuximaband demonstrates its potential for further clinical evaluation as a theranostic in prostate cancers and formed the basis for a Phase I imaging and therapy study planned for 2019. This study will use 89Zr-labelled Miltuximab to screen eligible patients and confirm tumour localisation, followed by treatment with 177Lu-labelled Miltuximab. Clinical trial information: ACTRN12616000787482.

The “ProPSMA Study” clinical trial protocol: A prospective randomized multi-center study of the impact of Ga-68 PSMA PET/CT imaging for staging high-risk prostate cancer prior to curative-intent surgery or radiotherapy

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Background: Disease persistence or relapse following curative-intent surgery or radiotherapy of high-risk prostate cancer is not uncommon. This is attributable, in part, to a failure of accurate staging with diagnostic imaging being insensitive for detection of small volume metastatic disease. Prostate-specific-membrane-antigen (PSMA) positron emission tomography/computed tomography (PET/CT) is a new whole body scanning technique that enables visualisation of prostate cancer with high sensitivity. The hypotheses of this study are that PSMA-PET/CT (a) has improved diagnostic accuracy compared to conventional imaging, (b) should be used as a first-line diagnostic test for staging, (c) the improved diagnostic accuracy will result in significant management impact and (d) provides economic benefits when incorporated into the management algorithm. Methods: This is a 300 patient phase III multi-centre randomized study of patients with untreated high-risk prostate cancer defined by Gleason grade group 3-5, PSA ≥ 20ng/ml or clinical stage ≥ T3. Patients are randomized to Gallium-68-PSMA11 PET/CT or conventional imaging, consisting of computer tomography of the abdomen/pelvis and bone scintigraphy with SPECT/CT. Patients with negative, equivocal or oligometastatic disease cross-over to receive the other imaging arm. The primary objective is to compare the accuracy of PSMA-PET/CT to conventional imaging for detecting nodal or distant metastatic disease. Accuracy is defined by a pre-defined “ground truth” scoring system incorporating histopathologic, imaging and clinical follow-up at six months post randomisation. Secondary objectives include comparing management impact, the number of equivocal studies, the incremental value of second-line imaging in patients who cross-over, health economics, radiation exposure, inter-observer agreement and safety of PSMA-PET/CT. Longer term follow-up will also assess the prognostic value of a negative PSMA-PET/CT. 294 of 300 (98%) patients randomised at time of abstract submission. Clinical trial information: 12617000005358.

Feasibility and accuracy of single time point imaging for renal dosimetry following 177Lu-DOTATATE ('Lutate') therapy

Background

This study aims to assess both feasibility and accuracy of renal dosimetry imaging protocols in patients receiving Lutate therapy for neuroendocrine tumours (NETs), when data acquisition over multiple days is not possible on all cycles.

Method

Patients who had received a full 4 cycles of Lutate therapy with complete imaging at each cycle were included. Imaging consisted of quantitative SPECT/CT of the kidneys at 4, 24 and 96–120 h post injection. Renal absorbed dose was calculated for each data set, and in addition, five alternative methods were explored for comparison. Method 1: a patient average clearance time (t_1/2 average) derived from the first half of contributing patient data was used to estimate absorbed dose for subsequent patients based on 4 h imaging alone; method 2: t_1/2 average was applied to subsequent patients on 24 h imaging alone; method 3: a patient-specific clearance rate (t_1/2 patient) was determined from complete image data of cycle 1 and applied subsequently to remaining cycles using 4 h image data alone; method 4: t_1/2 patient was applied to 24 h imaging alone in subsequent cycles; method 5: the 120 h data was estimated on subsequent cycles based on the cycle 1 fraction of injected activity (%IA) at 24 and 120 h.

Results

Twenty treatments from 18 patients, resulting in 80 cycles of therapy, were analysed. The measured average renal absorbed dose per cycle of treatment was 0.38 ± 0.19 Gy/GBq when derived from full imaging data. The use of t_1/2 average applied to a single time point led to large deviations of dose estimates from true values (on average 59% and 30%, when using 4 h data and 24 h data, respectively). The use of complete image data on cycle 1 and the derivation of t_1/2 patient led to improved dose estimates, with an average deviation from true values of 13% and 2% when using 4 h data only and 24 h data only, respectively. The use of a 120 h %IA derived from cycle 1 led to an average deviation from true dose estimates of 14%.

Conclusion

In instances where demands on both patients and facilities make multiple time point data acquisition impractical, renal dosimetry is best derived through complete imaging at cycle 1 only followed by a single 24 h imaging time point on subsequent cycles, assuming no significant changes in renal function during the time course of therapy.

SPECT V/Q in Lung Cancer Radiotherapy Planning

Curative-intent lung cancer radiation therapy either alone (RT) or combined with immuno-chemotherapy is associated with potential risk of serious radiation-induced lung injury. This review provides a summary of the role of SPECT ventilation perfusion (V/Q) imaging as an emerging adjunct to lung cancer RT planning and treatment dosimetry. Denoted "functional lung avoidance RT" it is hypothesized that preferential dosimetric avoidance of physiologically functional lung may reduce the frequency of radiation-induced lung injury. SPECT V/Q imaging datasets available during the planning process allows the prioritization (or "personalization') of RT dose to minimize the volume of functional lung probabilistically exposed to injurious radiation dose. Selective escalation of target dose and adaptive planning and replanning is also enabled. The emergent importance of the tumor-lung microenvironment and its biologic relationship to local immune effectors in lung cancer provides further incentive to individualize RT planning and delivery. This review examines important normal tissue dosimetric constraints that are part of current standards-of-care and the new dosimetric parameters associated with functional lung avoidance RT. SPECT V/Q has been a valuable tool in investigating the feasibility and efficacy of functional lung avoidance RT but is yet to become main stream due to the lack of large clinical trials. It is encouraging however that functional lung avoidance is feasible in RT dose-target delineation and some of the more promising studies are discussed.

FET PET in the evaluation of indeterminate brain lesions on MRI: Differentiating glioma from other non-neoplastic causes - A pilot study

We aimed to determine the utility of FET PET in the management of indeterminate CNS lesions found on MRI. We performed a retrospective analysis of patients with FET PET at a single tertiary institution from 2011 to 2015. FET PET images were processed using usual methods and measurements taken including SUVmax, TBRmax, and analysis of dynamic series where available (Kipeak, Vdpeak, as well as tumor:background ratio for these variables). Correlation studies were performed using ANOVA between cohorts of high-grade histology, low-grade histology, and benign histology/stable on observation. Thirty-five patients were included, of whom 34 were suitable for analysis with median follow-up of 5 months. The positive predictive value of FET PET in this cohort was 83.3%. FET SUVmax differentiated between patients with high-grade (mean SUV 3.38, 95% CI 2.21-4.55), low-grade (1.88, 95% CI 1.33-2.43) and benign/observation (1.42, 95% CI 1.13-1.71) cohorts (p = 0.0003). Similarly, tumour to brain ratio was significant (p < 0.0001). Kipeak distinguished between high grade and observation cohorts (p = 0.036), as did KiTBR (p = 0.025). Vd peak was not significantly different in these two cohorts (p = 0.057) but Vd TBR was (p = 0.041). In conclusion, FET PET demonstrated a high positive predictive value for glioma in patients with indeterminate brain lesions on MRI. The combination of negative FET and negative FDG PET scans may predict an indolent clinical course. Confirmatory trials are needed to establish the potential value of FET PET in guiding surgical management in this cohort.

Comparison of radiobiological parameters for 90Y radionuclide therapy (RNT) and external beam radiotherapy (EBRT) in vitro

Background

Dose rate variation is a critical factor affecting radionuclide therapy (RNT) efficacy. Relatively few studies to date have investigated the dose rate effect in RNT. Therefore, the aim of this study was to benchmark ⁹⁰Y RNT (at different dose rates) against external beam radiotherapy (EBRT) in vitro and compare cell kill responses between the two irradiation processes.

Results

Three human colorectal carcinoma (CRC) cell lines (HT29, HCT116, SW48) were exposed to ⁹⁰Y doses in the ranges 1–10.4 and 6.2–62.3 Gy with initial dose rates of 0.013–0.13 Gy/hr (low dose rate, LDR) and 0.077–0.77 Gy/hr (high dose rate, HDR), respectively. Results were compared to a 6-MV photon beam doses in the range from 1–9 Gy with constant dose rate of 277 Gy/hr. The cell survival parameters from the linear quadratic (LQ) model were determined. Additionally, Monte Carlo simulations were performed to calculate the average dose, dose rate and the number of hits in the cell nucleus.

For the HT29 cell line, which was the most radioresistant, the α/β ratio was found to be ≈ 31 for HDR–⁹⁰Y and ≈ 3.5 for EBRT. LDR–⁹⁰Y resulting in insignificant cell death compared to HDR–⁹⁰Y and EBRT. Simulation results also showed for LDR–⁹⁰Y, for doses ≲ 3 Gy, the average number of hits per cell nucleus is ≲ 2 indicating insufficiently delivered lethal dose. For ⁹⁰Y doses \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\gtrsim $\end{document}≳ 3 Gy the number of hits per nucleus decreases rapidly and falls below ≈ 2 after ≈ 5 days of incubation time. Therefore, our results demonstrate that LDR–⁹⁰Y is radiobiologically less effective than EBRT. However, HDR–⁹⁰Y at ≈ 56 Gy was found to be radiobiologically as effective as acute ≈ 8 Gy EBRT.

Conclusion

These results demonstrate that the efficacy of RNT is dependent on the initial dose rate at which radiation is delivered. Therefore, for a relatively long half-life radionuclide such as ⁹⁰Y, a higher initial activity is required to achieve an outcome as effective as EBRT.

A Comparison of 2D and 3D Kidney Absorbed Dose Measures in Patients Receiving 177Lu-DOTATATE

Objective(s):

To investigate and compare quantitative accuracy of kidney absorbed dose measures made from both 2D and 3D imaging in patients receiving ¹⁷⁷Lu-DOTATATE (Lutate) for treatment of neuroendocrine tumours (NETs).

Methods:

Patients receiving Lutate therapy underwent both whole body planar imaging and SPECT/CT imaging over the kidneys at time points 0.5, 4, 24, and 96-120 hours after injection. Planar data were corrected for attenuation using transmission data, and were converted to units of absolute activity via two methods, using either a calibration standard in the field of view or relative to pre-voiding image total counts. Hand drawn regions of interest were used to generate time activity curves and kidney absorbed dose estimates in OLINDA-EXM. Fully quantitative SPECT data were generated using CT-derived corrections for both scatter and attenuation, before correction for dead time and application of a camera specific sensitivity factor to convert data to units of absolute activity. Volumes of interest were defined for kidney using the co-registered x-ray CT, before time activity curves and absorbed dose measures were generated in OLINDA-EXM, both with and without corrections made to the model for patient specific kidney volumes. Quantitative SPECT data were also used to derive dose maps through dose kernel convolution (DKC), which was treated as the gold standard.

Results:

A total of 50 studies were analysed, corresponding to various cycles of treatment from 21 patients. Planar absorbed dose estimates were consistently higher than SPECT derived estimates by, on average, a factor of 3.

Conclusion:

Quantitative SPECT is considered the gold standard approach for organ specific dosimetry however often relies on in house software. As such planar methods for estimating absorbed dose are much more widely available, and in particular, are often the only source of reference in previously published data. For the case of Lutate dosimetry, planar measures may lead to a three-fold increase in measures of kidney absorbed dose.

A prospective randomized multicentre study of the impact of gallium-68 prostate-specific membrane antigen (PSMA) PET/CT imaging for staging high-risk prostate cancer prior to curative-intent surgery or radiotherapy (proPSMA study): clinical trial protocol

BACKGROUND

Accurate staging of patients with prostate cancer (PCa) is important for therapeutic decision-making. Relapse after surgery or radiotherapy of curative intent is not uncommon and, in part, represents a failure of staging with current diagnostic imaging techniques to detect disease spread. Prostate-specific membrane antigen (PSMA) positron-emission tomography (PET)/computed tomography (CT) is a new whole-body scanning technique that enables visualization of PCa with high contrast. The hypotheses of this study are that: (i) PSMA-PET/CT has improved diagnostic performance compared with conventional imaging; (ii) PSMA-PET/CT should be used as a first-line diagnostic test for staging; (iii) the improved diagnostic performance of PSMA-PET/CT will result in significant management impact; and (iv) there are economic benefits if PSMA-PET/CT is incorporated into the management algorithm.

OBJECTIVES AND METHODS

The proPSMA trial is a prospective, multicentre study in which patients with untreated high-risk PCa will be randomized to gallium-68-PSMA-11 PET/CT or conventional imaging, consisting of CT of the abdomen/pelvis and bone scintigraphy with single-photon emission CT/CT. Patients eligible for inclusion are those with newly diagnosed PCa with select high-risk features, defined as International Society of Urological Pathology grade group ≥3 (primary Gleason grade 4, or any Gleason grade 5), prostate-specific antigen level ≥20 ng/mL or clinical stage ≥T3. Patients with negative, equivocal or oligometastatic disease on first line-imaging will cross over to receive the other imaging arm. The primary objective is to compare the accuracy of PSMA-PET/CT with that of conventional imaging for detecting nodal or distant metastatic disease. Histopathological, imaging and clinical follow-up at 6 months will define the primary endpoint according to a predefined scoring system. Secondary objectives include comparing management impact, the number of equivocal studies, the incremental value of second-line imaging in patients who cross over, the cost of each imaging strategy, radiation exposure, inter-observer agreement and safety of PSMA-PET/CT. Longer-term follow-up will also assess the prognostic value of a negative PSMA-PET/CT.

OUTCOME AND SIGNIFICANCE

This trial will provide data to establish whether PSMA-PET/CT should replace conventional imaging in the primary staging of select high-risk localized PCa, or whether it should be used to provide incremental diagnostic information in selected cases.