Circulating androgen receptor gene amplification and resistance to 177Lu-PSMA-617 in metastatic castration-resistant prostate cancer: results of a Phase 2 trial

A Meta-Analysis and Meta-Regression of the Efficacy, Toxicity, and Quality of Life Outcomes Following Prostate-Specific Membrane Antigen Radioligand Therapy Utilising Lutetium-177 and Actinium-225 in Metastatic Prostate Cancer

BACKGROUND AND OBJECTIVE

Management of metastatic prostate cancer (mPCa) presents significant challenges. In this systematic review, meta-analysis, and meta-regression, the efficacy, safety, and quality of life (QoL) outcomes of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (PRLT) utilising lutetium-177 ([177Lu]Lu-PSMA) and actinium-225 ([225Ac]Ac-PSMA) were assessed.

METHODS

A detailed literature search across PubMed/Medline, EMBASE, Web of Science, Scopus, and Cochrane Library was conducted, culminating in the inclusion of 100 studies involving 8711 patients. Data on prostate-specific antigen (PSA) responses, toxicity profiles, and QoL and survival outcomes were analysed. Proportional meta-analyses and meta-regression analyses were performed.

KEY FINDINGS AND LIMITATIONS

The estimated proportion of patients with PSA decline ≥50% was 0.49 for [177Lu]Lu-PSMA and 0.60 for [225Ac]Ac-PSMA in mPCa, particularly metastatic castration-resistant prostate cancer. A meta-regression analysis indicated an association between the cumulative amount of administered activity and the proportion of PSA ≥50% decline. Positive PSA responses were observed alongside improved overall survival across both therapies. Our analyses also identified the key factors associated with PSA responses and survival outcomes, including baseline haemoglobin level, and the presence of visceral metastases. Although anaemia was commonly observed, with [177Lu]Lu-PSMA, severe toxicities were infrequent. Improved QoL was observed following [177Lu]Lu-PSMA therapy, whereas it remained stable following the second cycle of [225Ac]Ac-PSMA treatment. Heterogeneity across studies for PSA responses and toxicity profiles is a limitation.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Our findings suggest an association between PRLT and reductions in PSA levels, as well as associations with enhanced survival outcomes in mPCa. Furthermore, our analysis shows a low incidence of severe toxicity associated with this treatment. These observations highlight the important role of PRLT in the management of mPCa.

Study of predictive factors for response to 177LU-PSMA in patients with metastatic castration-resistant prostate cancer

Introduction

Metastatic castration-resistant prostate cancer (mCRPC) is an aggressive disease with a poor prognosis and few therapeutic options. In recent years, 177Lu-PSMA, a novel radioligand therapy, has shown promising results in patients who have failed conventional therapies. However, around 30% of patients do not respond adequately to this treatment. In this retrospective cohort study, we examined clinical, biological, and 68Ga-PSMA PET/CT-derived factors associated with poor treatment response.

Materials and methods

We conducted a retrospective cohort study including 63 patients treated at ICO Angers for progressive mCRPC following Novel Hormonal Agents and taxane-based chemotherapy. The primary endpoint was early treatment discontinuation, defined as stopping therapy at or before the 4th cycle. Secondary endpoints included PSA response and overall survival.

Results

A total of 63 patients were included in the study. Factors associated with early treatment discontinuation included a BMI < 25 kg/m2, PSA doubling time < 2 months, hemoglobin levels <10 g/dL, albumin levels <35 g/L, lactate dehydrogenase (LDH) levels >250 IU/L and alkaline phosphatase (ALP) levels >125 IU/L. On 68Ga-PSMA PET/CT imaging, low SULmax, high Total Tumor Volume, and a low PSG score were also linked to early treatment discontinuation.

Conclusion

This study identified several clinical, biological, and 68Ga-PSMA PET/CT-derived factors associated with early treatment discontinuation. Patients with poor overall health, aggressive or extensive disease, or low PSMA expression are at higher risk of treatment failure.

Assessment of the therapeutic efficacy of [177Lu]Lu-PSMA-X compared to taxane chemotherapy in taxane-chemo-naïve patients with metastatic castration-resistant prostate cancer: A systematic review and meta-analysis

INTRODUCTION AND AIM

Radioligand therapy (RLT) with 177Lu-labelled prostate specific membrane antigen ([177Lu]Lu-PSMA-X, referring with "PSMA-X" to a generic PSMA chemical compound) inhibitors has emerged as a viable treatment option in metastatic castration resistant prostate cancer patients having previously progressed on taxane and androgen receptor inhibitors. The aim of this study was to perform a systematic review and meta-analysis to assess the therapeutic efficacy of [177Lu]Lu-PSMA-X compared to taxane chemotherapy in taxane-chemo-naïve patients with metastatic castration-resistant prostate cancer.

MATERIALS AND METHODS

Searches in several bibliographic databases were made using relevant key words, and articles published up to March 2024 were included. The endpoints included prostate specific antigen (PSA) response rate (RR), progression-free survival, and overall survival. Individual patient data were pooled when feasible. PSA50 was defined as the median proportion of patients achieving at least a 50% decline in serum PSA from baseline. A meta-analysis of the PSA50 response rate (proportion meta-analysis) was performed, generating pooled estimates and 95% confidence intervals (95% CI).

RESULTS

From the initially selected 8,414 studies published between 2019 and 2023, 24 were included in the [177Lu]Lu-PSMA-X treated group and 17 in the taxane treated group. Our findings show that [177Lu]Lu-PSMA-X RLT yielded comparable PSA50 responses in taxane-naïve patients versus those receiving taxane chemotherapy, despite considerable study heterogeneity. Notably, the taxane-naïve group had more extensive pretreatment.

CONCLUSIONS

This meta-analysis combines the largest cohorts of taxane-naïve mCRPC patients treated with [177Lu]Lu-PSMA-X RLT and taxane-treated mCRPC. It underscores similar PSA50 response rates in both groups, suggesting a potential role for [177Lu]Lu-PSMA-X RLT in taxane-naïve patients who cannot or choose not to undergo chemotherapy.

Investigating the significance of SPECT/CT-SUV for monitoring 177Lu-PSMA-targeted radionuclide therapy: a systematic review

BACKGROUND

Quantitative molecular imaging via single-photon emission computed tomography-derived standardised uptake value (SPECT/CT-SUV) is used to assess the response of metastatic castration-resistant prostate cancer (mCRPC) patients to targeted radionuclide therapy (TRT) with [177Lu]Lu-PSMA. This imaging technique determines the radiopharmaceutical distribution and internal dosimetry in patients who receive TRT. However, there is limited evidence regarding the role of image quantification in monitoring changes induced by [177Lu]Lu-PSMA. This systematic examines the role of quantitative SPECT/CT-SUV during [177Lu]Lu-PSMA TRT and assesses whether SUV changes correlate with quantitative imaging and biomarkers.

METHODS

A systematic review was conducted in accordance with the PRISMA guidelines. The MEDLINE/PubMed databases were searched from January 2016 to July 2024 to identify relevant articles. The inclusion criterion was the use of quantitative SPECT/CT-SUV during [177Lu]Lu-PSMA TRT for patients with mCRPC. The records were screened to determine their eligibility. The abstracts of 62 records were screened, and 28 were excluded because they were not relevant; the full texts of 34 original papers were retrieved and assessed for eligibility.

RESULTS

A total of five studies were included in this systematic review (two prospective studies and three retrospective studies). The sample sizes of the studies ranged from 6 to 73 patients. The highest number of lesions analysed was 144. Three studies reported the SPECT/CT-SUV following cycle 1, and only one study reported the correlation with pretherapy PET/CT (r = 0.9, p = 0.005). SPECT/CT-SUV changes between the first two to three cycles were reported in one study. None of the studies reported the SPECT/CT-SUV for normal organs. One study reported correlations between SPECT/CT-derived SUV and PET/CT-derived SUV in target and nontarget tissues.

CONCLUSION

Quantitative SPECT/CT-SUV can be used to predict responses to subsequent PSMA-TRT cycles. Disease burden and tumour heterogeneity are the leading causes of TRT individualisation.

Impact of TP53 loss-of-function alterations on the response to PSMA radioligand therapy in metastatic castration-resistant prostate cancer patients

Rationale: PSMA-targeting radioligand therapy (PSMA-RLT) has shown promise in metastatic castration-resistant prostate cancer (mCRPC), particularly in PSMA-avid tumours. However, predicting response remains challenging. Preclinical data suggests aberrant p53-signalling as a predictor of poor response. Methods: The patient population of this pre-planned retrospective cohort study consists of 96 patients with mCRPC who underwent treatment with PSMA-RLT and were molecularly profiled by whole-genome sequencing and or targeted next-generation sequencing. Response to PSMA-RLT was assessed per molecular subtype, including TP53-mutational status. Results: Patients with TP53 loss-of-function alterations had a shorter median progression-free survival (3.7 versus 6.2 months, P<0.001), a lower median PSA change (-55% vs. -75%, P=0.012) and shorter overall survival from initiation of PMSA-RLT (7.6 vs. 13.9 months, P=0.003) compared to TP53-wildtype patients. Pathogenic alterations in AR, MYC, BRCA1, or BRCA2 as well as in genes linked to the PI3K or MAPK pathways or genes involved in homologous recombination repair, were not associated with response. Only lactate dehydrogenase was, alongside TP53-status, significantly associated with response. Transcriptome analysis of 21 patients, identified six p53 signalling genes whose low expression was associated to a shorter progression-free survival (P<0.05). Conclusion: TP53 loss-of-function may serve as a prognostic factor for PSMA-RLT outcomes in patients with mCRPC.

Review on the Increasing Role for PSMA-Based Radioligand Therapy in Prostate Cancer

In 2021, two randomized controlled trials (RCTs), TheraP and VISION, demonstrated that 177Lu-PSMA-617 as monotherapy was more effective for the decline of PSA than the comparator third-line treatments.

METHODS

Our review summarizes new RCTs that add to the use of radioligand therapy (RLT) for patients with high-risk prostate cancer (PCa).

RESULTS

Four past and present RCTs included 1081 patients. An RCT, ENZA-p, studied first-line treatment of patients with metastatic castration-resistant PCa (mCRPC). A combination of enzalutamide (ENZA) and 177Lu-PSMA-617 gave longer progression-free survival than ENZA as monotherapy. Other RCTs of patients with mCRPC, including the PSMAfore, and SPLASH trials, showed 177Lu-PSMA-617 as second-line treatment gave better progression-free survival than androgen receptor pathway inhibitors (combined p value < 6.9 × 10-6).

CONCLUSIONS

Patients with PCa gain if they are given PSMA-RLT early in the treatment of PCa and as part of combination therapies.

177Lu-PSMA therapy in metastatic prostate cancer: An updated review of prognostic and predictive biomarkers

177Lu-PSMA has been approved for the treatment of PSMA-positive metastatic castration-resistant (mCRPC) patients who progressed to androgen receptor pathway inhibitors (ARPIs) and taxane-based chemotherapy. However, a higher proportion of patients do not respond to this type of radioligand therapy (RLT). To date, there is a lack of validated prognostic and predictive biomarkers for 177Lu-PSMA therapy in prostate cancer. Several studies have investigated the prognostic and predictive role of clinical and molecular factors and also the metabolic features of PET imaging. In this review, we aim to take stock of the current scenario, focusing on new emerging data from retrospective/prospective series and clinical trials. Given the high costs and the possibility of primary resistance, it seems essential to identify clinical and molecular characteristics that could allow clinicians to choose the right patient to treat with 177Lu-PSMA. Biomarker-based clinical trials are urgently needed in this field.

Blood-based liquid biopsy in advanced prostate cancer

Prostate cancer is characterized by several genetic alterations which could impact prognosis and therapeutic decisions in the advanced disease. Tissue biopsy is still considered the gold standard approach for molecular characterization in prostate cancer, but it has several limitations, including the possibility of insufficient/inadequate tumor tissue to be analyzed. Blood-based liquid biopsy is a non-invasive method to investigate tumor cell derivatives in the bloodstream, being a valid alternative to tissue biopsy for molecular characterization but also for predictive and/or prognostic purposes. In this review, we analyze the most relevant evidence in this field, focusing on clinically relevant targets such as HRD genetic alterations and also focusing on the differences between tissue and liquid biopsy in light of the data from the latest clinical trials.

Impact of Somatic DNA Repair Mutations on the Clinical Outcomes of Bone Metastases from Castration-Resistant Prostate Cancer

Up to 80% of castration-resistant prostate cancer (CRPC) patients develop bone metastases during the natural history of disease and about 25% harbor mutations in DNA damage repair (DDR) genes. This retrospective observational study evaluated the prevalence of DDR alterations in CRPC patients and their effect on the clinical outcomes associated with bone metastases. The mutational status of CRPC patients was analyzed per FoundationOne® analysis in tissue biopsy or, when it was not possible, in liquid biopsy performed at the onset of metastatic CRPC (mCRPC). The impact of DDR gene mutations on bone-related efficacy endpoints was evaluated at the time of mCRPC diagnoses. In total, 121 mCRPC patients with bone metastases were included: 38 patients had mutations in at least one DDR gene, the remaining 83 ones had a non-mutated DDR status. DDR mutated status was associated with bone metastases volume (p = 0.006), but did not affect SRE (skeletal-related events) incidence and time to SRE onset. Liquid and tissue biopsies were both available for 61 patients with no statistically significant difference in terms of incidence and type of molecular DDR alterations. Mutated DDR status was associated with higher bone metastasic volume, although a not detrimental effect on the other bone-related efficacy endpoints was observed.

AR and PI3K Genomic Profiling of Cell-free DNA Can Identify Poor Responders to Lutetium-177-PSMA Among Patients with Metastatic Castration-resistant Prostate Cancer

Lutetium-177 prostate-specific membrane antigen radioligands (¹⁷⁷Lu-PSMA) are new therapeutic agents for the treatment of metastatic castration-resistant prostate cancer (mCRPC). We evaluated the prognostic value of circulating tumour DNA (ctDNA) profiling in patients with mCRPC starting treatment with ¹⁷⁷Lu-PSMA I&T. Between January 2020 and October 2022, patients with late-stage mCRPC (n = 57) were enrolled in a single-centre observational cohort study. Genomic alterations in the AR gene, PI3K signalling pathway, TP53, and TMPRSS2-ERG were associated with progression-free survival (PFS) on Kaplan-Meier and multivariable Cox regression analyses. Median PFS of 3.84 mo (95% confidence interval [CI] 3.3-5.4) was observed, and 21/56 (37.5%) evaluable patients experienced a prostate-specific antigen response of ≥50% during treatment. Among 46 patients who provided a blood sample for profiling before ¹⁷⁷Lu-PSMA treatment. ctDNA was detected in 39 (84.8%); higher ctDNA was correlated with shorter PFS. Genomic structural rearrangements in the AR gene (hazard ratio [HR] 9.74, 95% confidence interval [CI] 2.4-39.5; p = 0.001) and alterations in the PI3K signalling pathway (HR 3.58, 95% CI 1.41-9.08; p = 0.007) were independently associated with poor ¹⁷⁷Lu-PSMA prognosis on multivariable Cox regression. Prospective evaluation of these associations in biomarker-driven trials is warranted.

Patient summary

We examined cell-free DNA in blood samples from patients with advanced metastatic prostate cancer who started treatment with lutetium-177-PSMA, a new radioligand therapy. We found that patients with genetic alterations in the androgen receptor gene or PI3K pathway genes did not experience a lasting benefit from lutetium-177-PSMA.

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.

Genomic biomarkers to guide precision radiotherapy in prostate cancer

Our ability to prognosticate the clinical course of patients with cancer has historically been limited to clinical, histopathological, and radiographic features. It has long been clear however, that these data alone do not adequately capture the heterogeneity and breadth of disease trajectories experienced by patients. The advent of efficient genomic sequencing has led to a revolution in cancer care as we try to understand and personalize treatment specific to patient clinico-genomic phenotypes. Within prostate cancer, emerging evidence suggests that tumor genomics (e.g., DNA, RNA, and epigenetics) can be utilized to inform clinical decision making. In addition to providing discriminatory information about prognosis, it is likely tumor genomics also hold a key in predicting response to oncologic therapies which could be used to further tailor treatment recommendations. Herein we review select literature surrounding the use of tumor genomics within the management of prostate cancer, specifically leaning toward analytically validated and clinically tested genomic biomarkers utilized in radiotherapy and/or adjunctive therapies given with radiotherapy.

Radiotheranostics in oncology: current challenges and emerging opportunities

Structural imaging remains an essential component of diagnosis, staging and response assessment in patients with cancer; however, as clinicians increasingly seek to noninvasively investigate tumour phenotypes and evaluate functional and molecular responses to therapy, theranostics - the combination of diagnostic imaging with targeted therapy - is becoming more widely implemented. The field of radiotheranostics, which is the focus of this Review, combines molecular imaging (primarily PET and SPECT) with targeted radionuclide therapy, which involves the use of small molecules, peptides and/or antibodies as carriers for therapeutic radionuclides, typically those emitting α-, β- or auger-radiation. The exponential, global expansion of radiotheranostics in oncology stems from its potential to target and eliminate tumour cells with minimal adverse effects, owing to a mechanism of action that differs distinctly from that of most other systemic therapies. Currently, an enormous opportunity exists to expand the number of patients who can benefit from this technology, to address the urgent needs of many thousands of patients across the world. In this Review, we describe the clinical experience with established radiotheranostics as well as novel areas of research and various barriers to progress.

Lutetium Lu 177 Vipivotide Tetraxetan: First Approval

Lutetium Lu 177 vipivotide tetraxetan (PLUVICTO™, formerly known as ¹⁷⁷Lu-PSMA-617) is a radioligand therapeutic agent that is being developed by Advanced Accelerator Applications (a subsidiary of Novartis) for the treatment of prostate-specific membrane antigen (PSMA)-expressing metastatic prostate cancer. The active part of the radiopharmaceutical is lutetium-177, which is linked to a ligand that binds to prostate-specific membrane antigen (PSMA), a transmembrane enzyme overexpressed in primary and metastatic prostate cancers. Based on efficacy results from the phase 3 VISION trial, lutetium Lu 177 vipivotide tetraxetan was approved in the USA on 23 March 2022 for the treatment of adult patients with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) who have been treated with androgen receptor (AR) pathway inhibition and taxane-based chemotherapy. Regulatory review in the EU and other countries is underway. This article summarizes the milestones in the development of Lutetium Lu 177 vipivotide tetraxetan leading to this first approval as a therapeutic radioligand for mCRPC.

Recent advances in the treatment of advanced prostate cancer: maximizing existing therapies while searching for novel solutions

PURPOSE OF REVIEW

Present highlights from recent research examining treatment of advanced prostate cancer.

RECENT FINDINGS

Data are emerging that combining androgen deprivation, docetaxel, and additional androgen-receptor-targeted therapies in treatment naïve metastatic prostate cancer may be an effective strategy to improve outcomes. Genomically targeted therapies and radiopharmaceuticals continue to be evaluated in the treatment of advanced castration-resistant prostate cancer.

SUMMARY

Although no clear consensus has emerged regarding the best sequencing of available therapeutics, trial results continue to support moving available therapies earlier in the disease course. Data continue to build for novel radiopharmaceuticals soon to likely be approved for treatment of castration-resistant disease.

Precision Targets for Intercepting the Lethal Progression of Prostate Cancer: Potential Avenues for Personalized Therapy

Organ-confined prostate cancer of low-grade histopathology is managed with radiation, surgery, active surveillance, or watchful waiting and exhibits a 5-year overall survival (OS) of 95%, while metastatic prostate cancer (PCa) is incurable, holding a 5-year OS of 30%. Treatment options for advanced PCa-metastatic and non-metastatic-include hormone therapy that inactivates androgen receptor (AR) signaling, chemotherapy and genome-targeted therapy entailing synthetic lethality of tumor cells exhibiting aberrant DNA damage response, and immune checkpoint inhibition (ICI), which suppresses tumors with genomic microsatellite instability and/or deficient mismatch repair. Cancer genome sequencing uncovered novel somatic and germline mutations, while mechanistic studies are revealing their pathological consequences. A microRNA has shown biomarker potential for stratifying patients who may benefit from angiogenesis inhibition prior to ICI. A 22-gene expression signature may select high-risk localized PCa, which would not additionally benefit from post-radiation hormone therapy. We present an up-to-date review of the molecular and therapeutic aspects of PCa, highlight genomic alterations leading to AR upregulation and discuss AR-degrading molecules as promising anti-AR therapeutics. New biomarkers and druggable targets are shaping innovative intervention strategies against high-risk localized and metastatic PCa, including AR-independent small cell-neuroendocrine carcinoma, while presenting individualized treatment opportunities through improved design and precision targeting.