Novel Radiopharmaceuticals and Future of Theranostics in Genitourinary Cancers.

BACKGROUND AND OBJECTIVE: This review aims to provide an overview of novel diagnostic and therapeutic radiopharmaceuticals tested recently or used currently in genitourinary cancers within prospective phase 1-2 clinical trials, summarizing progresses and future directions. METHODS: A systematic search was conducted using the PubMed/MEDLINE and ClinicalTrials.gov databases for original prospective research studies following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. KEY FINDINGS AND LIMITATIONS: Forty-six papers were systematically reviewed; 74 ongoing clinical trials were identified. The results of 27 novel radiopharmaceuticals (ie, not approved by the Food and Drug Administration/European Medicines Agency and not listed in the Pharmacopeia) prospectively investigated in genitourinary cancers, mostly prostate, for diagnostic, theranostic, or therapeutic purposes (21, one, and five of the 27 radiopharmaceuticals, respectively) over the past 5 yr were presented. Most were prostate-specific membrane antigen-targeting agents (17/27); other targets included gastrin-releasing peptide receptor, carbonic anhydrase IX, Cu, six transmembrane epithelial antigen of the prostate 1, tumor-associated glycoprotein 42, and urokinase-type plasminogen activator receptor. Ongoing research confirms the same trend. Fibroblast activation protein inhibitor, PD-L1, CD8, nectin-4, and HER2 are other targets under investigation. Among the 22 ongoing therapeutic trials (out of the 74 ongoing clinical trials), targeted alpha therapy is being explored in 12, and five are evaluating combinations of radioligand therapy with other treatments. We confirmed the safety of radiopharmaceuticals (regardless of the diagnostic/therapeutic purpose) and showed promising results in terms of diagnostic accuracy and therapeutic efficacy in genitourinary cancers. CONCLUSIONS AND CLINICAL IMPLICATIONS: There continues to be expansion in radiopharmaceutical approaches to genitourinary cancers, reflecting a strong emphasis on improving tumor detection and treatment, which will likely impact future management across the disease spectrum, with the potential for improved patient care and outcomes.

Radiotherapy and theranostics: a Lancet Oncology Commission.

Following on from the 2015 Lancet Oncology Commission on expanding global access to radiotherapy, Radiotherapy and theranostics: a Lancet Oncology Commission was created to assess the access and availability of radiotherapy to date and to address the important issue of access to the promising field of theranostics at a global level. A marked disparity in the availability of radiotherapy machines between high-income countries and low-income and middle-income countries (LMICs) has been identified previously and remains a major problem. The availability of a suitably trained and credentialled workforce has also been highlighted as a major limiting factor to effective implementation of radiotherapy, particularly in LMICs. We investigated initiatives that could mitigate these issues in radiotherapy, such as extended treatment hours, hypofractionation protocols, and new technologies. The broad implementation of hypofractionation techniques compared with conventional radiotherapy in prostate cancer and breast cancer was projected to provide radiotherapy for an additional 2·2 million patients (0·8 million patients with prostate cancer and 1·4 million patients with breast cancer) with existing resources, highlighting the importance of implementing new technologies in LMICs. A global survey undertaken for this Commission revealed that use of radiopharmaceutical therapy-other than 131I-was highly variable in high-income countries and LMICs, with supply chains, workforces, and regulatory issues affecting access and availability. The capacity for radioisotope production was highlighted as a key issue, and training and credentialling of health professionals involved in theranostics is required to ensure equitable access and availability for patient treatment. New initiatives-such as the International Atomic Energy Agency's Rays of Hope programme-and interest by international development banks in investing in radiotherapy should be supported by health-care systems and governments, and extended to accelerate the momentum generated by recognising global disparities in access to radiotherapy. In this Commission, we propose actions and investments that could enhance access to radiotherapy and theranostics worldwide, particularly in LMICs, to realise health and economic benefits and reduce the burden of cancer by accessing these treatments.

PSMA PET/CT patterns of recurrence after mono-brachytherapy in men with low and intermediate prostate cancer and subsequent management.

PURPOSE: Brachytherapy as monotherapy is a recommended treatment option for men with low to intermediate risk prostate cancer. Local recurrence is difficult to identify. This study investigated PSMA PET/CT for recurrence after brachytherapy, as well as their subsequent management when recurrence occurred only within the prostate. METHODS: We performed a retrospective single-center analysis for patients who were treated with brachytherapy as monotherapy for prostate cancer from May 2002 to May 2021 and who underwent a PSMA PET/CT for BCR. We report the findings on PSMA PET/CT, quantitative parameters, as well as the later management of the patients. RESULTS: Forty patients were identified, who underwent PSMA PET/CT to investigate a rising PSA at a median (IQR) of 7 years (3.0-10.8) after initial therapy. Median (IQR) PSA at time of PSMA PET/CT was 6.54 ng/mL (3.9-15.5). On PSMA PET/CT, 20/40 (50%) men had prostate-only recurrence. Of the 20 patients with prostate-only recurrence, 8/20 (40%) had recurrence in a high-dose radiation zone, versus 7/20 (35%) in an under-covered zone. On PSMA PET/CT, recurrence within the prostate had median (IQR) SUVmax 10.4 (5.1-15.7) and volume 2.9 mL (2.0-11.2). Subsequent management of these patients with local recurrence included surveillance followed by ADT (9/20, 45%). For those with surveillance followed by ADT, the mean time before introduction of ADT was 4.1 years (range 1-8 years).

Evolving Paradigms in Prostate Cancer: The Integral Role of Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography in Primary Staging and Therapeutic Decision-Making.

Prostate-specific membrane antigen (PSMA) positron emission tomography or computed tomography (PET/CT) has emerged as a superior imaging option to conventional imaging for prostate cancer. The majority of early evidence and prospective trials evaluated PSMA PET/CT in the biochemical recurrence or metastatic setting. However, there has been an increasing number of prospective trials in the primary setting. The purpose of this narrative review was to describe the role of PSMA PET/CT in localized primary prostate cancer. This narrative review focuses on the prospective evidence available in this setting. We detail the current practice and future potential for PSMA PET/CT to be used in multiple stages of localized primary prostate cancer. The most common practice currently for PSMA PET/CT is in the primary nodal and metastatic staging of high-risk prostate cancer. We describe other roles of PSMA PET/CT, including in intermediate-risk prostate cancer as well as local staging and the impact on radiation therapy and surgical management. We also discuss the potential future roles of PSMA PET/CT in prediagnosis such as risk stratification for biopsy, prognosis, and specific surgical roles. Potential pitfalls of PSMA PET/CT are also addressed. PSMA PET/CT has already had a significant influence on prostate cancer, and there will continue to be a greater role for this imaging modality in localized primary prostate cancer.

Sequential [177Lu]Lu-PSMA-617 and docetaxel versus docetaxel in patients with metastatic hormone-sensitive prostate cancer (UpFrontPSMA): a multicentre, open-label, randomised, phase 2 study.

BACKGROUND: Lutetium-177 [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 improves survival and quality of life in patients with metastatic castration-resistant prostate cancer, but whether it confers a benefit in hormone-sensitive disease is unknown. We aimed to evaluate [177Lu]Lu-PSMA-617 before docetaxel treatment in patients with de-novo high-volume metastatic hormone-sensitive prostate cancer. METHODS: UpFrontPSMA was an investigator-initiated, multicentre, open-label, randomised, phase 2 trial done at 11 Australian hospitals. Eligible patients had prostate adenocarcinoma without clinically significant neuroendocrine differentiation or small-cell histology, were aged 18 years or older, had less than 4 weeks on androgen deprivation therapy, had an Eastern Cooperative Oncology Group performance status of 0-2, and had high-volume PSMA-avid disease on [68Ga]Ga-PSMA-11 PET-CT with no major discordance on 2-[18F] fluorodeoxyglucose-PET-CT. Patients were randomly assigned (1:1) to the experimental treatment ([177Lu]Lu-PSMA-617 followed 6 weeks later by docetaxel) or standard-of-care treatment (docetaxel alone) using computer-based block randomisation with random block sizes, stratified by disease volume by conventional imaging and duration of androgen deprivation therapy at the time of registration. Neither patients nor investigators were masked to treatment assignment. Patients in the experimental group received two cycles of [177Lu]Lu-PSMA-617 7·5 GBq every 6 weeks intravenously, followed 6 weeks later by six cycles of docetaxel 75 mg/m2 every 3 weeks intravenously, whereas patients in the standard-of-care treatment group received six cycles of docetaxel 75 mg/m2 every 3 weeks intravenously. All patients received continuous androgen deprivation therapy. The primary endpoint was undetectable prostate-specific antigen (≤0·2 ng/mL) at 48 weeks, assessed using a modified intention-to-treat analysis. The trial is registered with ClinicalTrials.gov, NCT04343885. FINDINGS: Between May 5, 2020, and April 18, 2023, 130 patients were randomly assigned, 63 (48%) to [177Lu]Lu-PSMA-617 plus docetaxel and 67 (52%) to docetaxel alone. All patients were male and no race or ethnicity data were collected. Median follow-up was 2·5 years (IQR 1·8-3·0). Four patients in the docetaxel alone group withdrew consent after randomisation and no data beyond screening were collected. An additional four patients were not evaluable for the primary endpoint at 48 weeks (two in each group). 25 (41%) of 61 patients (95% CI 30-54) in the [177Lu]Lu-PSMA-617 plus docetaxel group had undetectable PSA at 48 weeks compared with ten (16%) of 61 patients (9-28) in the docetaxel alone group (OR 3·88, 95% CI 1·61-9·38; p=0·0020). The most common grade 3 or 4 treatment-related adverse events were febrile neutropenia (seven [11%] of 63 patients in the [177Lu]Lu-PSMA-617 plus docetaxel group vs six [10%] of 63 patients in the docetaxel alone group) and diarrhoea (four [6%] of 63 patients vs none). Serious adverse events occurred in 16 (25%) patients in the [177Lu]Lu-PSMA-617 plus docetaxel group (none were definitely related to [177Lu]Lu-PSMA-617) and 16 (25%) patients in the docetaxel alone group. No treatment-related deaths occurred. INTERPRETATION: [177Lu]Lu-PSMA-617 followed by docetaxel improved antitumour activity in patients with de-novo high-volume metastatic hormone-sensitive prostate cancer compared with docetaxel alone, without increased toxic effects. Our data potentially support a role for [177Lu]Lu-PSMA-617 in metastatic hormone-sensitive prostate cancer. FUNDING: Prostate Cancer Research Alliance (Movember Foundation and Australian Government Medical Research Future Fund), US Department of Defence Impact Award-Clinical Trials, Endocyte/Advanced Accelerator Applications (a Novartis company), Australian Nuclear Science and Technology Organization, Victorian Cancer Agency, University of Melbourne, and Peter MacCallum Cancer Foundation.

Lu-177 PSMA vs Comparator Treatments and Survival in Metastatic Castration-Resistant Prostate Cancer.

Importance: Observed treatment effects on overall survival (OS) differed substantially in the first 2 randomized clinical trials of lutetium Lu 177 vipivotide tetraxetan (Lu-177) prostate-specific membrane antigen (PSMA) in metastatic castration-resistant prostate cancer. Objective: To investigate factors associated with the observed difference in treatment effects on OS, including differences in the risk of crossover from randomized treatment after disease progression. Design, Setting, and Participants: This comparative effectiveness study used individual participant data from 2 randomized clinical trials, TheraP (A Randomised Phase 2 Trial of 177Lu-PSMA617 Theranostic Versus Cabazitaxel in Progressive Metastatic Castration Resistant Prostate Cancer [ANZUP Protocol 1603]) (n = 200), recruited from February 2018 to September 2019 in Australia, and published data from VISION (An International, Prospective, Open Label, Multicenter, Randomized Phase 3 Study of 177Lu-PSMA-617 in the Treatment of Patients With Progressive PSMA-Positive Metastatic Castration-Resistant Prostate Cancer) (n = 831), recruited from June 2018 to October 2019 in North America and Europe. Individual participant data for OS were reconstructed from VISION using the published survival curves. Data were analyzed February 6, 2018, to December 31, 2021, for TheraP and June 4, 2018, to January 27, 2021, for VISION. Interventions: TheraP randomized participants to receive treatment with Lu-177 PSMA or cabazitaxel. VISION randomized participants to receive treatment with or without Lu-177 PSMA in addition to physicians' choice of protocol-permitted treatments (PPT; approved hormonal treatments [such as abiraterone and enzalutamide], bisphosphonates, radiotherapy, denosumab, or glucocorticoids), excluding cabazitaxel. Main Outcomes and Measures: Patient characteristics, treatment protocols, and OS outcomes of the 2 trials were compared. Estimates of the effect on OS from TheraP were adjusted for crossover from randomly assigned treatment using a rank-preserving structural failure time model (RPSFTM) and inverse probability of censoring weights (IPCW) methods. Results: The 200 participants in TheraP and 831 participants in VISION were similar in age (median [range], 72 [49-86] vs 71 [40-94] years). Improved OS was observed in the comparator treatment group (cabazitaxel) in TheraP compared with VISION (PPT) (hazard ratio [HR], 0.53 [95% CI, 0.39-0.71]). The Lu-177 PSMA treatment groups in TheraP and VISION had similar OS (HR, 0.92 [95% CI, 0.70-1.19]). In TheraP, 20 of 101 participants in the cabazitaxel group crossed over to Lu-177 PSMA, while 32 of 99 participants in the Lu-177 PSMA arm crossed over to cabazitaxel. No statistically significant differences in OS between the Lu-177 PSMA and cabazitaxel groups of TheraP were observed after controlling for crossover to cabazitaxel: RPSFTM HR, 0.97 (95% CI, 0.60-1.58); IPCW HR, 0.92 (95% CI, 0.65-1.32); RPSFTM HR, 0.97 (95% CI, 0.60-1.58) and IPCW HR, 0.82 (95% CI, 0.54-1.24) for crossover to Lu-177 PSMA; RPSFTM HR, 0.96 (95% CI, 0.53-1.74) and IPCW HR, 0.82 (95% CI, 0.53-1.27) for crossover to either Lu-177 PSMA or cabazitaxel. Conclusions and Relevance: Findings of this secondary analysis of the TheraP and VISION randomized clinical trials suggest that the choice of comparator treatments (ie, cabazitaxel vs PPT) may explain the difference in the observed effect of Lu-177 PSMA on OS between the 2 trials. Causal inference methods such as RPSFTM and IPCW may help rule out crossover as a plausible explanation.

Neoadjuvant lutetium PSMA, the TIME and immune response in high-risk localized prostate cancer.

High-risk localized prostate cancer remains a lethal disease with high rates of recurrence, metastases and death, despite attempts at curative local treatment including surgery. Disease recurrence is thought to be a result of failure of local control and occult micrometastases. Neoadjuvant strategies before surgery have been effective in many cancers, but, to date, none has worked in this setting for prostate cancer. Prostate-specific membrane antigen (PSMA)-based theranostics is an exciting and rapidly evolving field in prostate cancer. The novel intravenous radionuclide therapy, [177Lu]Lu-PSMA-617 (lutetium PSMA) has been shown to be effective in treating men with metastatic castration-resistant prostate cancer, targeting cells expressing PSMA throughout the body. When given in a neoadjuvant setting, lutetium PSMA might also improve long-term oncological outcomes in men with high-risk localized disease. A component of radiotherapy is potentially an immunogenic form of cancer cell death. Lutetium PSMA could cause cancer cell death, resulting in release of tumour antigens and induction of a tumour-specific systemic immune response. This targeted radioligand treatment has the potential to treat local and systemic tumour sites by directly targeting cells that express PSMA, but might also act indirectly via this systemic immune response. In selected patients, lutetium PSMA could potentially be combined with systemic immunotherapies to augment the antitumour T cell response, and this might produce long-lasting immunity in prostate cancer.

18F-DCFPyL PSMA PET/CT Tracheobronchial Uptake in Patients with Prostate Cancer: Incidence and Etiology.

We evaluated the incidence and potential etiology of tracheobronchial uptake in patients being evaluated by 18F-DCFPyL PET/CT for prostate cancer (PCa). Methods: The study included a consecutive 100 PCa patients referred for 18F-DCFPyL PET/CT. The PET/CT scans were retrospectively reviewed. The presence or absence of physiologic tracheobronchial uptake on PET/CT was recorded. To further evaluate tracheal prostate-specific membrane antigen (PSMA) expression, immunohistochemistry was performed on tracheal samples taken from 2 men who had surgical resection of lung cancer. Results: Tracheal uptake was present in 31 of 100 patients (31%). When tracheal uptake was present, the SUVmax was significantly higher in the left main bronchus (mean, 2.7) than in the right (mean, 2.3) (P < 0.001). Histopathologic testing of tracheobronchial samples showed PSMA expression in bronchial submucosal glands. Conclusion: In PCa patients undergoing 18F-DCFPyL PET/CT, tracheobronchial uptake occurred in 31% of patients. This is attributed to normal physiologic PSMA expression in bronchial submucosal glands.

Clinical Trial Protocol for VIOLET: A Single-Center, Phase I/II Trial Evaluation of Radioligand Treatment in Patients with Metastatic Castration-Resistant Prostate Cancer with [161Tb]Tb-PSMA-I&T.

[177Lu]Lu-PSMA is an effective class of therapy for patients with metastatic castration-resistant prostate cancer (mCRPC); however, progression is inevitable. The limited durability of response may be partially explained by the presence of micrometastatic deposits, which are energy-sheltered and receive low absorbed radiation with 177Lu due to the approximately 0.7-mm mean pathlength. 161Tb has abundant emission of Auger and conversion electrons that deposit a higher concentration of radiation over a shorter path, particularly to single tumor cells and micrometastases. 161Tb has shown in vitro and in vivo efficacy superior to that of 177Lu. We aim to demonstrate that [161Tb]Tb-PSMA-I&T will deliver effective radiation to sites of metastatic prostate cancer with an acceptable safety profile. Methods: This single-center, single-arm, phase I/II trial will recruit 30 patients with mCRPC. Key eligibility criteria include a diagnosis of mCRPC with progression after at least one line of taxane chemotherapy (unless medically unsuitable) and androgen receptor pathway inhibitor; prostate-specific membrane antigen-positive disease on [68Ga]Ga-PSMA-11 or [18F]DCFPyL PET/CT (SUVmax ≥ 20); no sites of discordance on [18F]FDG PET/CT; adequate bone marrow, hepatic, and renal function; an Eastern Cooperative Oncology Group performance status of no more than 2, and no prior treatment with another radioisotope. The dose escalation is a 3 + 3 design to establish the safety of 3 prespecified activities of [161Tb]Tb-PSMA-I&T (4.4, 5.5, and 7.4 GBq). The maximum tolerated dose will be defined as the highest activity level at which a dose-limiting toxicity occurs in fewer than 2 of 6 participants. The dose expansion will include 24 participants at the maximum tolerated dose. Up to 6 cycles of [161Tb]Tb-PSMA-I&T will be administered intravenously every 6 wk, with each subsequent activity reduced by 0.4 GBq. The coprimary objectives are to establish the maximum tolerated dose and safety profile (Common Terminology Criteria for Adverse Events version 5.0) of [161Tb]Tb-PSMA-I&T. Secondary objectives include measuring absorbed radiation dose (Gy), evaluating antitumor activity (prostate-specific antigen 50% response rate, radiographic and prostate-specific antigen progression-free survival, overall survival, objective response rate), and evaluating pain (Brief Pain Inventory-Short Form) and health-related quality of life (Functional Assessment of Cancer Therapy-Prostate and Functional Assessment of Cancer Therapy-Radionuclide Therapy). Conclusion: Enrollment was completed in February 2024. Patients are still receiving [161Tb]Tb-PSMA-I&T.

Combination Strategies and Targeted Radionuclide Therapies.

Combination models utilising treatments from two or more therapeutic classes are well established in cancer care. In the new era of theranostic (theragnostic) medicine there is an ongoing need to identify and refine novel combination strategies to optimise multidisciplinary care for conditions commonly encountered in nuclear medicine such as neuroendocrine neoplasms (NEN), prostate cancer (PCa), and thyroid cancer, along with seeking advancements in molecular imaging and therapy techniques for other tumour streams. This concise review explores the background of theranostic monotherapy, established approaches to combination strategies in theranostics, and emerging targeted radionuclide therapies in use or under active investigation, with a focus on Australian-led studies.

Functional Lung Avoidance Planning Using Multicriteria Optimization.

PURPOSE: Functional lung avoidance (FLA) radiation therapy is an evolving field. The aim of FLA planning is to reduce dose to areas of functioning lung, with comparable target coverage and dose to organs at risk. Multicriteria optimization (MCO) is a planning tool that may assist with FLA planning. This study assessed the feasibility of using MCO to adapt radiation therapy plans to avoid functional regions of lung that were identified using a 68Ga-4D-V/Q positron emission tomography/computed tomography. METHODS AND MATERIALS: A prospective clinical trial U1111-1138-4421 was performed in which patients had a 68Ga-4D-V/Q positron emission tomography/computed tomography before radiation treatment. Of the 72 patients enrolled in this trial, 38 patients had stage III non-small cell lung cancer and were eligible for selection into this planning study. Functional lung target volumes HF lung (highly functioning lung) and F lung (functional lung) were defined using the ventilated and perfused lung. Using knowledge-based planning, a baseline anatomic plan was created, and then a functional adapted plan was generated using multicriteria optimization. The primary aim was to spare dose to HF lung. Using the MCO tools, a clinician selected the final FLA plan. Dose to functional lung, target volumes, organs at risk and measures of plan quality were compared using standard statistical methods. RESULTS: The HF lung volume was successfully spared in all patients. The F lung volume was successfully spared in 36 of the 38 patients. There were no clinically significant differences in dose to anatomically defined organs at risk. There were differences in the planning target volume near maximum and minimum doses. Across the entire population, there was a statistically significant reduction in the functional mean lung dose but not in the functional volume receiving 20 Gy. All trade-off decisions were made by the clinician. CONCLUSIONS: Using MCO for FLA was achievable but did result in changes to planning target volume coverage. A distinct advantage in using MCO was that all decisions regarding the cost and benefits of FLA could be made in real time.

Beyond Prostate Imaging Reporting and Data System: Combining Magnetic Resonance Imaging Prostate Imaging Reporting and Data System and Prostate-Specific Membrane Antigen-Positron Emission Tomography/Computed Tomography PRIMARY Score in a Composite (P) Score for More Accurate Diagnosis of Clinically Significant Prostate Cancer.

PURPOSE: The Prostate Imaging Reporting and Data System (PI-RADS) score is standard of care for clinically significant prostate cancer (csPCa) diagnosis. The PRIMARY score (prostate-specific membrane antigen [PSMA]-positron emission tomography [PET]/CT) also has high diagnostic accuracy for csPCa. This study aimed to develop an easily calculated combined (P) score for csPCa detection (International Society of Urological Pathology [ISUP] ≥2) incorporating separately read PI-RADS and PRIMARY scores, with external validation. MATERIALS AND METHODS: Two datasets of men with suspected PCa, no prior biopsy, recent MRI and 68Ga-PSMA-11-PET/CT, and subsequent transperineal biopsy were evaluated. These included the development sample (n = 291, 56% csPCa) a prospective trial and the validation sample (n = 227, 67% csPCa) a multicenter retrospective database. Primary outcome was detection of csPCa (ISUP ≥2), with ISUP ≥ 3 cancer detection a secondary outcome. Score performance was evaluated by area under the curve, sensitivity, specificity, and decision curve analysis. RESULTS: The 5-point combined (P) score was developed in a prospective dataset. In the validation dataset, csPCa was identified in 0%, 20%, 52%, 96%, and 100% for P score 1 to 5. The area under the curve was 0.93 (95% CI: 0.90-0.96), higher than PI-RADS 0.89 (95% CI: 0.85-0.93, P = .039) and PRIMARY score alone 0.84 (95% CI: 0.79-0.89, P < .001). Splitting scores at 1/2 (negative) vs 3/4/5 (positive), P score sensitivity was 94% (95% CI: 89-97) compared to PI-RADS 89% (95% CI: 83-93) and PRIMARY score 86% (95% CI: 79-91). For ISUP ≥ 3, P score sensitivity was 99% (95% CI: 95-100) vs 94% (95% CI: 88-98) and 92% (95% CI: 85-97) for PI-RADS and PRIMARY scores respectively. A maximum standardized uptake value > 12 (P score 5) was ISUP ≥ 2 in all cases with 93% ISUP ≥ 3. CONCLUSIONS: The P score is easily calculated and improves accuracy for csPCa over both PI-RADS and PRIMARY scores. It should be considered when PSMA-PET is undertaken for diagnosis.

Comparison of quantitative whole body PET parameters on [68Ga]Ga-PSMA-11 PET/CT using ordered Subset Expectation Maximization (OSEM) vs. bayesian penalized likelihood (BPL) reconstruction algorithms in men with metastatic castration-resistant prostate cancer.

BACKGROUND: PSMA PET/CT is a predictive and prognostic biomarker for determining response to [177Lu]Lu-PSMA-617 in patients with metastatic castration resistant prostate cancer (mCRPC). Thresholds defined to date may not be generalizable to newer image reconstruction algorithms. Bayesian penalized likelihood (BPL) reconstruction algorithm is a novel reconstruction algorithm that may improve contrast whilst preventing introduction of image noise. The aim of this study is to compare the quantitative parameters obtained using BPL and the Ordered Subset Expectation Maximization (OSEM) reconstruction algorithms. METHODS: Fifty consecutive patients with mCRPC who underwent [68Ga]Ga-PSMA-11 PET/CT using OSEM reconstruction to assess suitability for [177Lu]Lu-PSMA-617 therapy were selected. BPL algorithm was then used retrospectively to reconstruct the same PET raw data. Quantitative and volumetric measurements such as tumour standardised uptake value (SUV)max, SUVmean and Molecular Tumour Volume (MTV-PSMA) were calculated on both reconstruction methods. Results were compared (Bland-Altman, Pearson correlation coefficient) including subgroups with low and high-volume disease burdens (MTV-PSMA cut-off 40 mL). RESULTS: The SUVmax and SUVmean were higher, and MTV-PSMA was lower in the BPL reconstructed images compared to the OSEM group, with a mean difference of 8.4 (17.5%), 0.7 (8.2%) and - 21.5 mL (-3.4%), respectively. There was a strong correlation between the calculated SUVmax, SUVmean, and MTV-PSMA values in the OSEM and BPL reconstructed images (Pearson r values of 0.98, 0.99, and 1.0, respectively). No patients were reclassified from low to high volume disease or vice versa when switching from OSEM to BPL reconstruction. CONCLUSIONS: [68Ga]Ga-PSMA-11 PET/CT quantitative and volumetric parameters produced by BPL and OSEM reconstruction methods are strongly correlated. Differences are proportional and small for SUVmean, which is used as a predictive biomarker. Our study suggests that both reconstruction methods are acceptable without clinical impact on quantitative or volumetric findings. For longitudinal comparison, committing to the same reconstruction method would be preferred to ensure consistency.

[177Lu]Lu-PSMA-617 plus enzalutamide in patients with metastatic castration-resistant prostate cancer (ENZA-p): an open-label, multicentre, randomised, phase 2 trial.

BACKGROUND: Enzalutamide and lutetium-177 [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 both improve overall survival in patients with metastatic castration-resistant prostate cancer. Androgen and PSMA receptors have a close intracellular relationship, with data suggesting complementary benefit if targeted concurrently. In this study, we assessed the activity and safety of enzalutamide plus adaptive-dosed [177Lu]Lu-PSMA-617 versus enzalutamide alone as first-line treatment for metastatic castration-resistant prostate cancer. METHODS: ENZA-p was an open-label, randomised, controlled phase 2 trial done at 15 hospitals in Australia. Participants were men aged 18 years or older with metastatic castration-resistant prostate cancer not previously treated with docetaxel or androgen receptor pathway inhibitors for metastatic castration-resistant prostate cancer, gallium-68 [68Ga]Ga-PSMA-PET-CT (PSMA-PET-CT) positive disease, Eastern Cooperative Oncology Group performance status of 0-2, and at least two risk factors for early progression on enzalutamide. Participants were randomly assigned (1:1) by a centralised, web-based system using minimisation with a random component to stratify for study site, disease burden, use of early docetaxel, and previous treatment with abiraterone acetate. Patients were either given oral enzalutamide 160 mg daily alone or with adaptive-dosed (two or four doses) intravenous 7·5 GBq [177Lu]Lu-PSMA-617 every 6-8 weeks dependent on an interim PSMA-PET-CT (week 12). The primary endpoint was prostate-specific antigen (PSA) progression-free survival, defined as the interval from the date of randomisation to the date of first evidence of PSA progression, commencement of non-protocol anticancer therapy, or death. The analysis was done in the intention-to-treat population, using stratified Cox proportional hazards regression. This trial is registered with ClinicalTrials.gov, NCT04419402, and participant follow-up is ongoing. FINDINGS: 162 participants were randomly assigned between Aug 17, 2020, and July 26, 2022. 83 men were assigned to the enzalutamide plus [177Lu]Lu-PSMA-617 group, and 79 were assigned to the enzalutamide group. Median follow-up in this interim analysis was 20 months (IQR 18-21), with 32 (39%) of 83 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 16 (20%) of 79 patients in the enzalutamide group remaining on treatment at the data cutoff date. Median age was 71 years (IQR 64-76). Median PSA progression-free survival was 13·0 months (95% CI 11·0-17·0) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 7·8 months (95% CI 4·3-11·0) in the enzalutamide group (hazard ratio 0·43, 95% CI 0·29-0·63, p<0·0001). The most common adverse events (all grades) were fatigue (61 [75%] of 81 patients), nausea (38 [47%]), and dry mouth (32 [40%]) in the enzalutamide plus [177Lu]Lu-PSMA-617 group and fatigue (55 [70%] of 79), nausea (21 [27%]), and constipation (18 [23%]) in the enzalutamide group. Grade 3-5 adverse events occurred in 32 (40%) of 81 patients in the enzalutamide plus [177Lu]Lu-PSMA-617 group and 32 (41%) of 79 patients in the enzalutamide group. Grade 3 events that occurred only in the enzalutamide plus [177Lu]Lu-PSMA-617 group included anaemia (three [4%] of 81 participants) and decreased platelet count (one [1%] participant). No grade 4 or 5 events were attributed to treatment on central review in either group. INTERPRETATION: The addition of [177Lu]Lu-PSMA-617 to enzalutamide improved PSA progression-free survival providing evidence of enhanced anticancer activity in patients with metastatic castration-resistant prostate cancer with risk factors for early progression on enzalutamide and warrants further evaluation of the combination more broadly in metastatic prostate cancer. FUNDING: Prostate Cancer Research Alliance (Movember and Australian Federal Government), St Vincent's Clinic Foundation, GenesisCare, Roy Morgan Research, and Endocyte (a Novartis company).

Emerging Theranostics for Prostate Cancer and a Model of Prostate-specific Membrane Antigen Therapy.

There is increasing demand worldwide to develop diagnostic and therapeutic (theranostic) markers for prostate cancer. One target of interest is prostate-specific membrane antigen (PSMA), a protein which is overexpressed in prostate cancer cells. Over the past decade, a growing body of literature has demonstrated that radiolabeled ligands that target PSMA show favorable clinical response and survival outcomes in patients with advanced prostate cancer. This focused review provides background to the development of PSMA as a target, an overview of key studies informing our current approach to radioligand-based imaging and therapy for prostate cancer, and a model for real-world implementation of PSMA theranostics based on an Australian experience.