ENZA-p trial protocol: a randomized phase II trial using prostate-specific membrane antigen as a therapeutic target and prognostic indicator in men with metastatic castration-resistant prostate cancer treated with enzalutamide (ANZUP 1901)

[68Ga]PSMA-11 for positron emission tomography (PET) imaging of prostate-specific membrane antigen (PSMA)-positive lesions in men with prostate cancer

INTRODUCTION

Theranostics targeting prostate-specific membrane antigen (PSMA) represent a new targeted approach for prostate cancer care that combines diagnostic and therapeutic radiopharmaceuticals to diagnose and treat the disease. Positron emission tomography (PET) is the imaging method of choice and several diagnostic radiopharmaceuticals for quantifying PSMA have received FDA approval and are in clinical use. [68Ga]Ga-PSMA-11 is one such imaging agent and the focus of this article. One beta-emitting radioligand therapy ([177Lu]Lu-PSMA-617) has also received FDA approval for prostate cancer treatment, and several other alpha- and beta-emitting radioligand therapies are in clinical trials.

AREAS COVERED

Theranostics targeting PSMA in men with prostate cancer are discussed with a focus on use of [68Ga]Ga-PSMA-11 for imaging PSMA-positive lesions in men with prostate cancer. The review covers [68Ga]Ga-PSMA-11 manufacture, current regulatory status, comparison of [68Ga]Ga-PSMA-11 to other imaging techniques, clinical updates, and emerging applications of artificial intelligence for [68Ga]Ga-PSMA-11 PET.

EXPERT OPINION

[68Ga]Ga-PSMA-11 is used in conjunction with a PET/CT scan to image PSMA positive lesions in men with prostate cancer. It is manufactured by chelating precursor with68Ga, either from a generator or cyclotron, and has regulatory approval around the world. It is widely used clinically in conjunction with radioligand therapies like [177Lu]Lu-PSMA-617.

RECIP 1.0 Predicts Progression-Free Survival After [177Lu]Lu-PSMA Radiopharmaceutical Therapy in Patients with Metastatic Castration-Resistant Prostate Cancer

Response Evaluation Criteria in Prostate-Specific Membrane Antigen Imaging (RECIP) 1.0 is an evidence-based framework to evaluate therapeutic efficacy in metastatic prostate cancer using prostate-specific membrane antigen (PSMA) PET/CT. This study aimed to evaluate the associations of interim PSMA PET/CT by RECIP 1.0 with short-term outcome after radiopharmaceutical treatment. Methods: This multicenter retrospective study included patients with metastatic castration-resistant prostate cancer who underwent [177Lu]Lu-PSMA radiopharmaceutical therapy at 3 academic centers and received PSMA PET/CT at baseline and at 12 wk. Pairs of PSMA PET/CT images were assessed by 5 readers for visual RECIP 1.0. The primary outcome was the association of RECIP with prostate-specific antigen progression-free survival (PSA-PFS) by Kaplan-Meier analysis. Results: In total, 124 of 287 screened patients met the inclusion criteria, with 0 (0%), 29 (23%), 54 (44%), and 41 (33%) of those 124 patients having complete response, partial response, stable disease, or progressive disease (PD) by visual RECIP 1.0, respectively. Patients with visual RECIP PD had a significantly shorter PSA-PFS than those with RECIP stable disease or with RECIP partial response (2.6 vs. 6.4 vs. 8.4 mo; P < 0.001). The median PSA-PFS among patients with RECIP PD versus those with non-RECIP PD was 2.6 versus 7.2 mo (hazard ratio, 13.0; 95% CI, 7.0-24.1; P < 0.001). Conclusion: PSMA PET/CT by RECIP 1.0 after 2 cycles of [177Lu]Lu-PSMA is prognostic for PSA-PFS. PSMA PET/CT by RECIP 1.0 may be used in earlier stages of prostate cancer to evaluate drug efficacy and to predict progression-free survival.

[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.

Theranostics revolution in prostate cancer: Basics, clinical applications, open issues and future perspectives

In the last years, theranostics has expanded the therapeutic options available for prostate cancer patients. In this review, we explore this dynamic field and its potential to revolutionize precision medicine for prostate cancer. We delve into the foundational principles, clinical applications, and emerging opportunities, emphasizing the potential synergy between radioligand therapy and other systemic treatments. Additionally, we address the ongoing challenges, including optimizing patient selection, assessing treatment responses, and determining the role of theranostics within the broader landscape of prostate cancer treatment.

The real-world outcomes of Lutetium-177 PSMA-617 radioligand therapy in metastatic castration-resistant prostate cancer: Turkish Oncology Group multicenter study

Metastatic castration-resistant prostate cancer (mCRPC) remains a challenging condition to treat despite recent advancements. This retrospective study aimed to assess the activity and tolerability of Lutetium-177 (Lu-177) PSMA-617 radioligand therapy (RLT) in mCRPC patients across multiple cancer centers in Turkey. The study included 165 patients who received at least one cycle of Lu-177 PSMA-617 RLT, with the majority having bone metastases and undergone prior treatments. Prostate-specific antigen (PSA) levels were assessed before each treatment cycle, and the biochemical response was evaluated in accordance with the Prostate Cancer Work Group 3 Criteria. The PSA decline of ≥50% was classified as a response, while an increase of ≥25% in PSA levels was indicative of progressive disease. Neither response nor progression was considered as stable disease. The Lu-177 PSMA-617 RLT led to a significant PSA response, with 50.6% of patients achieving a >50% decrease in PSA levels. Median overall survival (OS) and progression-free survival were 13.5 and 8.2 months, respectively. Patients receiving Lu-177 PSMA-617 RLT in combination with androgen receptor pathway inhibitors (ARPIs) had a higher OS compared to those receiving Lu-177 PSMA-617 RLT alone (18.2 vs 12.3 months, P = .265). The treatment was generally well-tolerated, with manageable side effects such as anemia and thrombocytopenia. This study provides real-world evidence supporting the effectiveness and safety of Lu-177 PSMA-617 RLT in mCRPC patients, particularly when used in combination with ARPIs. These findings contribute to the growing body of evidence on the potential benefits of PSMA-targeted therapies in advanced prostate cancer.

Towards Improving the Efficacy of PSMA-Targeting Radionuclide Therapy for Late-Stage Prostate Cancer-Combination Strategies

PURPOSE OF REVIEW

[177Lu]Lu-PSMA-617 is a radiopharmaceutical that emits beta-minus radiation and targets prostate-specific membrane antigen (PSMA)-positive prostate cancer. Despite its clinical success, there are still patients not showing sufficient response rates. This review compiles latest studies aiming at therapy improvement in [177Lu]Lu-PSMA-617-naïve and -resistant patients by alternative or combination treatments.

RECENT FINDINGS

A variety of agents to combine with [177Lu]Lu-PSMA-617 are currently under investigation including alpha radiation-emitting pharmaceuticals, radiosensitizers, taxane chemotherapeutics, androgen receptor pathway inhibitors, immune checkpoint inhibitors, and external beam radiation. Actinium-225 (225Ac)-labeled PSMA-targeting inhibitors are the most studied pharmaceuticals for combination therapy or as an alternative for treatment after progression under [177Lu]Lu-PSMA-617 therapy. Alpha emitters seem to have a potential of achieving a response to PSMA-targeting radionuclide therapy in both initial non-responders or responders to [177Lu]Lu-PSMA-617 later developing treatment resistance. Emerging evidence for immunostimulatory effects of radiopharmaceuticals and first prospective studies support the combination of [177Lu]Lu-PSMA-617 and immune checkpoint inhibition for late-stage prostate cancer.

Synthesis and Evaluation of ePSMA-DM1: A New Theranostic Small-Molecule Drug Conjugate (T-SMDC) for Prostate Cancer

Small-molecule drug conjugates (SMDCs) are compounds in which a therapeutic payload is conjugated to a targeting vector, for specific delivery to the tumor site. This promising approach can be translated to the treatment of prostate cancer by selecting a targeting vector which binds to the prostate-specific membrane antigen (PSMA). Moreover, the addition of a bifunctional chelator to the molecule allows for the use of both diagnostic and therapeutic radionuclides. In this way, the distribution of the SMDC in the body can be monitored, and combination therapy regimes can be implemented. We combined a glutamate-urea-lysine vector to the cytotoxic agent DM1 and a DOTA chelator via an optimized linker to obtain the theranostic SMDC (T-SMDC) ePSMA-DM1. ePSMA-DM1 retained a high binding affinity to PSMA and demonstrated PSMA-specific uptake in cells. Glutathione stability assays showed that the half-life of the T-SMDC in a reducing environment was 2 h, and full drug release was obtained after 6 h. Moreover, 100 nM of ePSMA-DM1 reduced the cell viability of the human PSMA-positive LS174T cells by >85% after 72 h of incubation, which was comparable to a 10-fold higher dose of free DM1. [111In]In-ePSMA-DM1 and [177Lu]Lu-ePSMA-DM1 were both obtained in high radiochemical yields and purities (>95%), with >90% stability in PBS and >80% stability in mouse serum for up to 24 h post incubation at 37 °C. SPECT/CT imaging studies allowed for a faint tumor visualization of [111In]In-ePSMA-DM1 at 1 h p.i., and the ex vivo biodistribution showed tumor uptake (2.39 ± 0.29% ID/g) at 1 h p.i., with the compound retained in the tumor for up to 24 h. Therefore, ePSMA-DM1 is a promising T-SMDC candidate for prostate cancer, and the data obtained so far warrant further investigations, such as therapeutic experiments, after further optimization.

Lutetium-177 PSMA for the treatment of metastatic castrate resistant prostate cancer: a systematic review

INTRODUCTION

Metastatic castrate resistant prostate cancer (mCPRC) remains an aggressive form of prostate cancer that no longer responds to traditional hormonal treatment alone. Despite the advent of novel anti-androgen medications, many patients continue to progress, and as a result, there is a growing need for additional treatment options.

AREAS COVERED

Lutetium-177 (177Lu) - PSMA-617 has become one of the new frontline treatment options for refractory metastatic castrate resistant prostate cancer after the failure of novel anti-androgen therapy and chemotherapy. Lu-177 has been used in real-world prospective trials and is now becoming utilized in newer phase III clinical trials. Here, we present a comprehensive overview of the current literature, covering retrospective studies, prospective studies, and clinical trials that established Lutetium-177-PSMA-617 (177Lu-PSMA-617) for the treatment of mCRPC.

EXPERT OPINION

177Lu - PSMA-617 has been approved for treatment of mCRPC based on positive phase III studies. While this treatment is tolerable and effective, biomarkers are necessary to determine which patients will benefit. In the future, radioligand treatments will likely be utilized in earlier lines of therapy and potentially in combination with other prostate cancer treatments.

Personalized [177Lu]Lutetium-PSMA Therapy for Patients with Pre-Treated Castration-Resistant Prostate Cancer: A Single Institution Experience from a Comprehensive Cancer Centre

Castration resistant prostate cancer (CRPC) is characterized by an aggressive biological behavior with a relatively short survival time, especially in progressive tumors pretreated with new hormonal agents and taxane chemotherapy. [177Lu]-Lutetium-PSMA (Lu-PSMA) treatment has proven efficacy in these patients. However, around 30% of the CRPC patients do not benefit from Lu-PSMA treatment, and little is known about predictive factors for treatment success if Lu-PSMA is offered in an individualized approach based on clinical and laboratory features. In this monocentric retrospective study, 86 CRPC patients receiving Lu-PSMA treatment were evaluated. The focus of the study was to describe clinical factors at baseline and during early treatment that are related to overall survival (OS). In addition, PSMA PET/CT-, PSA-response, and safety and tolerability (CTCAE adverse event reporting) were assessed. Efficacy endpoints were calculated using stratified Kaplan-Meier methods and Cox regression models. Mean applied dose was 17.7 GBq (mean 5.3 ± 1.1 GBq per cycle) with an average of 3.6 (range 1-8) therapy cycles. Patients were followed up for a mean of 12.4 months (range 1-39). The median OS was 15 months (95% CI 12.8-17.2). The best overall response rate in patients assessed with PSMA PET/CT and PSA response was 27.9%, and 50.0% had at least stable disease. Nine patients had a ≥grade 3 adverse event with anemia being the most frequent adverse event. Positive predictors for prolonged OS from baseline parameters were pre-treatment hemoglobin level of ≥10 g/dL and a lower PSA values at treatment start, while the presence of visceral or liver metastases were not significantly associated with worse prognoses in this cohort. With careful patient selection, an individualized Lu-PSMA treatment approach is feasible and patients with dose-limiting factors or visceral metastases should be included in prospective trials.

Preclinical Evaluation of a PSMA-Targeting Homodimer with an Optimized Linker for Imaging of Prostate Cancer

Prostate-specific membrane antigen (PSMA) targeting radiopharmaceuticals have been successfully used for diagnosis and therapy of prostate cancer. Optimization of the available agents is desirable to improve tumor uptake and reduce side effects to non-target organs. This can be achieved, for instance, via linker modifications or multimerization approaches. In this study, we evaluated a small library of PSMA-targeting derivatives with modified linker residues, and selected the best candidate based on its binding affinity to PSMA. The lead compound was coupled to a chelator for radiolabeling, and subject to dimerization. The resulting molecules, 22 and 30, were highly PSMA specific (IC₅₀ = 1.0-1.6 nM) and stable when radiolabeled with indium-111 (>90% stable in PBS and mouse serum up to 24 h). Moreover, [¹¹¹In]In-30 presented a high uptake in PSMA expressing LS174T cells, with 92.6% internalization compared to 34.1% for PSMA-617. Biodistribution studies in LS174T mice xenograft models showed that [¹¹¹In]In-30 had a higher tumor and kidney uptake compared to [¹¹¹In]In-PSMA-617, but increasing T/K and T/M ratios at 24 h p.i. Tumors could be clearly visualized at 1 h p.i. by SPECT/CT after administration of [¹¹¹In]In-22 and [¹¹¹In]In-PSMA-617, while [¹¹¹In]In-30 showed a clear signal at later time-points (e.g., 24 h p.i.).

177Lu-PSMA SPECT Quantitation at 6 Weeks (Dose 2) Predicts Short Progression-Free Survival for Patients Undergoing 177Lu-PSMA-I&T Therapy

177Lu-PSMA is an effective treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and adjust treatment may be improved using predictive tools. This study aimed to evaluate change in 177Lu-PSMA SPECT quantitative parameters to monitor treatment response. Methods: One hundred twenty-seven men with progressive mCRPC previously treated with androgen-signaling inhibition (99%) and chemotherapy (71%) received a median of 3 (interquartile range [IQR], 2-5) 8-GBq (IQR, 8-8.5 GBq) doses of 177Lu-PSMA-I&T. Imaging included 68Ga-PSMA-11 PET/CT (SUVmax > 15 at a single site and > 10 at all sites > 2 cm), diagnostic CT, and 177Lu SPECT/CT from vertex to mid thigh (24 h after treatment). 177Lu SPECT/CT quantitative analysis was undertaken at cycles 1 (baseline) and 2 (week 6) of treatment. Clinical and biochemical results were assessed to evaluate prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival (OS). Results: A PSA reduction of more than 50% was seen in 58% (74/127). The median PSA PFS was 6.1 mo (95% CI, 5.5-6.7), and OS was 16.8 mo (95% CI, 13.5-20.1). At the time of analysis, 41% (52/127) were deceased. At baseline and week 6, 76% (96/127) had analyzable serial 177Lu SPECT/CT imaging. SPECT total tumor volume (TTV) was reduced between baseline and week 6 in 74% (71/96; median, -193; IQR, -486 to -41). Any increase in SPECT TTV between baseline and week 6 was associated with significantly shorter PSA PFS (hazard ratio, 2.5; 95% CI, 1.5-4.2; P = 0.0008) but not OS. Median PSA PFS in those with an increase in SPECT TTV was 3.7 mo (95% CI, 2.8-6.8), compared with 6.7 mo (95% CI, 5.8-10.6) in those with no increase in SPECT TTV. An increase in SPECT TTV greater than 20% was also associated with PSA PFS (hazard ratio, 1.9; 95% CI, 1.2-3.0; P = 0.008) but less significantly than any change in SPECT TTV. There was a significant difference in PSA PFS between patients with both increased PSA and SPECT TTV and patients with reduced SPECT TTV and PSA (median, 2.8 vs. 9.0 mo; P < 0.0001). Conclusion: Increasing PSMA SPECT TTV on quantitative 177Lu SPECT/CT predicts short progression-free survival and may play a future role as an imaging response biomarker, identifying when to cease or intensify 177Lu-PSMA therapy.

Evaluation of 177Lu-PSMA-617 SPECT/CT Quantitation as a Response Biomarker Within a Prospective 177Lu-PSMA-617 and NOX66 Combination Trial (LuPIN)

¹⁷⁷Lu-PSMA-617 is an effective and novel treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and therefore efficacy may be improved using predictive tools. This study investigated the predictive value of serial ¹⁷⁷Lu-PSMA-617 SPECT/CT (¹⁷⁷Lu SPECT) imaging in monitoring treatment response. Methods: Fifty-six men with progressive mCRPC previously treated with chemotherapy and novel androgen signaling inhibitor were enrolled into the LuPIN trial and received up to 6 doses of ¹⁷⁷Lu-PSMA-617 and a radiation sensitizer (3-(4-hydroxyphenyl)-2H-1-benzopyran-7-ol [NOX66]). ⁶⁸Ga-PSMA-11 and ¹⁸F-FDG PET/CT were performed at study entry and exit, and ¹⁷⁷Lu SPECT from vertex to mid thighs was performed 24 h after each treatment. SPECT quantitative analysis was undertaken at cycles 1 (baseline) and 3 (week 12) of treatment. Results: Thirty-two of the 56 men had analyzable serial ¹⁷⁷Lu SPECT imaging at both cycle 1 and cycle 3. In this subgroup, median prostate-specific antigen (PSA) progression-free survival (PFS) was 6.3 mo (95% CI, 5-10 mo) and median overall survival was 12.3 mo (95% CI, 12-24 mo). The PSA 50% response rate was 63% (20/32). ¹⁷⁷Lu SPECT total tumor volume (SPECT TTV) was reduced in 68% (22/32; median, -0.20 m³ [95% CI, -1.4 to -0.001]) and increased in 31% (10/32; median, 0.36 [95% CI, 0.1-1.4]). Any increase in SPECT TTV was associated with shorter PSA PFS (hazard ratio, 4.1 [95% CI, 1.5-11.2]; P = 0.006). An increase of 30% or more in SPECT TTV was also associated with a shorter PSA PFS (hazard ratio, 3.3 [95% CI, 1.3-8.6]; P =0.02). Tumoral SUV_max was reduced in 91% (29/32) and SUV_mean in 84% (27/32); neither was associated with PSA PFS or overall survival outcomes. PSA progression by week 12 was also associated with a shorter PSA PFS (hazard ratio, 26.5 [95% CI, 5.4-131]). In the patients with SPECT TTV progression at week 12, 50% (5/10) had no concurrent PSA progression (median PSA PFS, 4.5 mo [95% CI, 2.8-5.6 mo]), and 5 of 10 men had both PSA and SPECT TTV progression at week 12 (median PSA PFS, 2.8 mo [95% CI, 1.8-3.7 mo]). Conclusion: Increasing SPECT TTV on quantitative ¹⁷⁷Lu SPECT predicts a short PFS and may play a future role as an imaging response biomarker.

The Prognostic Value of Posttreatment 68Ga-PSMA-11 PET/CT and 18F-FDG PET/CT in Metastatic Castration-Resistant Prostate Cancer Treated with 177Lu-PSMA-617 and NOX66 in a Phase I/II Trial (LuPIN)

¹⁷⁷Lu-PSMA-617 therapy has shown high prostate-specific antigen (PSA) response rates in men with metastatic castration-resistant prostate cancer. However, early treatment resistance is common. This LuPIN substudy aimed to determine the prognostic value of posttreatment quantitative PET for PSA progression-free survival (PFS) and overall survival (OS) with ¹⁷⁷Lu-PSMA-617 therapy. Methods: Fifty-six men with progressive metastatic castration-resistant prostate cancer were enrolled in the LuPIN trial and received up to 6 doses of ¹⁷⁷Lu-PSMA-617 and a radiation sensitizer (NOX66). ⁶⁸Ga-PSMA-11 and ¹⁸F-FDG PET/CT, diagnostic CT, and bone scanning were performed at study entry and exit. Quantitative analysis tracked change in total tumor volume (TTV) and SUV. Univariable and multivariable analyses were conducted to examine the association of change in TTV (continuous and >30%), SUV_max, PSA, and radiographic progression with PSA PFS and OS. Results: All men (37/56) who underwent both screening and posttreatment molecular imaging were analyzed; 70% (26/37) had a PSA response of more than 50%. Median PSA PFS was 8.6 mo, and median OS was 22 mo. Clinical progression had occurred at trial exit in 54% (20/37). In response to treatment, a reduced PSMA SUV_max was demonstrated in 95% (35/37) and a reduced PSMA TTV in 68% (25/37). An increase in PSMA TTV by at least 30% was associated with worse OS (median, 10.2 vs. 23.6 mo; P = 0.002). Change in PSMA SUV_max was not associated with PSA PFS or OS. ¹⁸F-FDG SUV_max was reduced in 51% (18/35) and ¹⁸F-FDG TTV in 67% (22/35). An increased ¹⁸F-FDG SUV_max was associated with worse OS (median, 20.7 vs. 25.7 mo; P < 0.01). An ¹⁸F-FDG TTV increase by more than 30% was associated with a short PSA PFS (median, 3.5 vs. 8.6 mo; P < 0.001) but not OS. Both PSA and radiographic progression were associated with shorter OS (median, 14.5 vs. 25.7 mo [P < 0.001] and 12.2 vs. 23.6 mo [P = 0.002]). On multivariable analysis, only increased PSMA TTV and PSA progression remained independently prognostic of OS (hazard ratio, 5.1 [95% CI, 1.5-17.1; P = 0.008] and 3.5 [95% CI, 1.1-10.9; P = 0.03], respectively). Conclusion: Change in quantitative PSMA TTV has strong potential as a prognostic biomarker with ¹⁷⁷Lu-PSMA-617 therapy, independent of ¹⁸F-FDG PET parameters, PSA, or radiographic progression. Further research into the value of posttreatment PET as an imaging biomarker is warranted.

Status of PSMA-targeted radioligand therapy in prostate cancer: current data and future trials

Metastatic prostate cancer continues to be an incurable disease. Despite all the novel therapies approved in the past two decades, overall patient outcomes remain relatively poor, and these patients die on a regular basis. Clearly, improvements in current therapies are needed. Prostate-specific membrane antigen (PSMA) is a target for prostate cancer given its increased expression on the surface of the prostate cancer cells. PSMA small molecule binders include PSMA-617 and PSMA-I&T and monoclonal antibodies such as J591. These agents have been linked to different radionuclides including beta-emitters such as lutetium-177 and alpha-emitters such as actinium-225. The only regulatory-approved PSMA-targeted radioligand therapy (PSMA-RLT) to date is lutetium-177-PSMA-617 in the setting of PSMA-positive metastatic castration-resistant prostate cancer that has failed androgen receptor pathway inhibitors and taxane chemotherapy. This approval was based on the phase III VISION trial. Many other clinical trials are evaluating PSMA-RLT in various settings. Both monotherapy and combination studies are underway. This article summarizes pertinent data from recent studies and provides an overview of human clinical trials in progress. The field of PSMA-RLT is rapidly evolving, and this therapeutic approach will likely play an increasingly important role in the years to come.

Using PSMA imaging for prognostication in localized and advanced prostate cancer

The use of prostate-specific membrane antigen (PSMA)-directed applications in modern prostate cancer management has evolved rapidly over the past few years, helping to establish new treatment pathways and provide further insights into prostate cancer biology. However, the prognostic implications of PSMA-PET have not been studied systematically, owing to rapid clinical implementation without long follow-up periods to determine intermediate-term and long-term oncological outcomes. Currently available data suggest that traditional prognostic factors and survival outcomes are associated with high PSMA expression (both according to immunohistochemistry and PET uptake) in men with localized and biochemically recurrent disease. Treatment with curative intent (primary and/or salvage) often fails when PSMA-positive metastases are present; however, the sensitivity of PSMA-PET in detecting all metastases is poor. Low PSMA-PET uptake in recurrent disease is a favourable prognostic factor; however, it can be associated with poor prognosis in conjunction with high ¹⁸F-fluorodeoxyglucose uptake in metastatic castration-resistant prostate cancer. Clinical trials embedding PSMA-PET for guiding management with reliable oncological outcomes are needed to support ongoing clinical use.

Pharmacological Optimization of PSMA-Based Radioligand Therapy

Prostate cancer (PCa) is the most common malignancy in men of middle and older age. The standard treatment strategy for PCa ranges from active surveillance in low-grade, localized PCa to radical prostatectomy, external beam radiation therapy, hormonal treatment and chemotherapy. Recently, the use of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) for metastatic castration-resistant PCa has been approved. PSMA is predominantly, but not exclusively, expressed on PCa cells. Because of its high expression in PCa, PSMA is a promising target for diagnostics and therapy. To understand the currently used RLT, knowledge about pharmacokinetics (PK) and pharmacodynamics (PD) of the PSMA ligand and the PSMA protein itself is crucial. PK and PD properties of the ligand and its target determine the duration and extent of the effect. Knowledge on the concentration-time profile, the target affinity and target abundance may help to predict the effect of RLT. Increased specific binding of radioligands to PSMA on PCa cells may be associated with better treatment response, where nonspecific binding may increase the risk of toxicity in healthy organs. Optimization of the radioligand, as well as synergistic effects of concomitant agents and an improved dosing strategy, may lead to more individualized treatment and better overall survival.

Management of Patients with Advanced Prostate Cancer: Report from the Advanced Prostate Cancer Consensus Conference 2021

BACKGROUND

Innovations in treatments, imaging, and molecular characterisation in advanced prostate cancer have improved outcomes, but various areas of management still lack high-level evidence to inform clinical practice. The 2021 Advanced Prostate Cancer Consensus Conference (APCCC) addressed some of these questions to supplement guidelines that are based on level 1 evidence.

OBJECTIVE

To present the voting results from APCCC 2021.

DESIGN, SETTING, AND PARTICIPANTS

The experts identified three major areas of controversy related to management of advanced prostate cancer: newly diagnosed metastatic hormone-sensitive prostate cancer (mHSPC), the use of prostate-specific membrane antigen ligands in diagnostics and therapy, and molecular characterisation of tissue and blood. A panel of 86 international prostate cancer experts developed the programme and the consensus questions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The panel voted publicly but anonymously on 107 pre-defined questions, which were developed by both voting and non-voting panel members prior to the conference following a modified Delphi process.

RESULTS AND LIMITATIONS

The voting reflected the opinions of panellists and did not incorporate a standard literature review or formal meta-analysis. The answer options for the consensus questions received varying degrees of support from panellists, as reflected in this article and the detailed voting results reported in the Supplementary material.

CONCLUSIONS

These voting results from a panel of experts in advanced prostate cancer can help clinicians and patients to navigate controversial areas of management for which high-level evidence is scant. However, diagnostic and treatment decisions should always be individualised according to patient characteristics, such as the extent and location of disease, prior treatment(s), comorbidities, patient preferences, and treatment recommendations, and should also incorporate current and emerging clinical evidence and logistic and economic constraints. Enrolment in clinical trials should be strongly encouraged. Importantly, APCCC 2021 once again identified salient questions that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference is a forum for discussing current diagnosis and treatment options for patients with advanced prostate cancer. An expert panel votes on predefined questions focused on the most clinically relevant areas for treatment of advanced prostate cancer for which there are gaps in knowledge. The voting results provide a practical guide to help clinicians in discussing treatment options with patients as part of shared decision-making.

177Lu-PSMA Radioligand Therapy Is Favorable as Third-Line Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer. A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

In this systematic review and network meta-analysis (NMA), we aimed to assess the benefits and harms of third-line (L3) treatments in randomized controlled trials (RCTs) of patients with metastatic castration-resistant prostate cancer (mCRPC). Two reviewers searched for publications from 1 January 2006 to 30 June 2021. The review analyzed seven RCTs that included 3958 patients and eight treatments. Treatment with prostate-specific membrane antigen (PSMA)-based radioligand therapy (PRLT) resulted in a 1.3-times-higher rate of median PSA decline ≥50% than treatment with abiraterone, enzalutamide, mitoxantrone, or cabazitaxel (p = 0.00001). The likelihood was 97.6% for PRLT to bring about the best PSA response, out of the examined treatments. PRLT resulted in a 1.1-times-higher six-month rate of median radiographic progression-free survival. Treatment with PRLT in the VISION trial resulted in 1.05-times-higher twelve-month median overall survival than L3 treatment with cabazitaxel in other RCTs. PRLT more often resulted in severe thrombocytopenia and less often in severe leukopenia than did cabazitaxel. In conclusion, for patients with mCRPC, L3 treatment with PRLT is highly effective and safe.