Response Prediction of 177Lu-PSMA-617 Radioligand Therapy Using Prostate-Specific Antigen, Chromogranin A, and Lactate Dehydrogenase

PROX1 drives neuroendocrine plasticity and liver metastases in prostate cancer

With the widespread use of anti-androgen therapy, such as abiraterone and enzalutamide, the incidence of neuroendocrine prostate cancer (NEPC) is increasing. NEPC is a lethal form of prostate cancer (PCa), with a median overall survival of less than one year after diagnosis. In addition to the common bone metastases seen in PCa, NEPC exhibits characteristics of visceral metastases, notably liver metastasis, which serves as an indicator of a poor prognosis clinically. Key factors driving the neuroendocrine plasticity of PCa have been identified, yet the underlying mechanism behind liver metastasis remains unclear. In this study, we identified PROX1 as a driver of neuroendocrine plasticity in PCa, responsible for promoting liver metastases. Mechanistically, anti-androgen therapy alleviates transcriptional inhibition of PROX1. Subsequently, elevated PROX1 levels drive both neuroendocrine plasticity and liver-specific transcriptional reprogramming, promoting liver metastases. Moreover, liver metastases in PCa induced by PROX1 depend on reprogrammed lipid metabolism, a disruption that effectively reduces the formation of liver metastases.

Circulating Biomarkers Predictive of Treatment Response in Patients with Hormone-sensitive or Castration-resistant Metastatic Prostate Cancer: A Systematic Review

BACKGROUND AND OBJECTIVE

Metastatic prostate cancer (mPCa) harbors genomic alterations that may predict targeted therapy efficacy. These alterations can be identified not only in tissue but also directly in biologic fluids (ie, liquid biopsies), mainly blood. Liquid biopsies may represent a safer and less invasive alternative for monitoring patients treated for mPCa. Current research focuses on the description and validation of novel predictive biomarkers to improve precision medicine in mPCa. Our aim was to systematically review the current evidence on liquid biopsy biomarkers for predicting treatment response in mPCa.

METHODS

We systematically searched Medline, Web of Science, and evidence-based websites for publications on circulating biomarkers in mPCa between March 2013 and February 2024 for review. Endpoints were: prediction of overall survival, biochemical or radiographic progression-free survival after treatment (chemotherapy, androgen deprivation therapy, androgen receptor pathway inhibitors [ARPIs], immunotherapy, or PARP inhibitors [PARPIs]). For each biomarker, the level of evidence (LOE) for clinical validity was attributed: LOE IA and IB, high level of evidence; LOE IIB and IIC, intermediate level; and LOE IIIC and LOE IV-VD, weak level.

KEY FINDINGS AND LIMITATIONS

The predictive value of each biomarker for the response to several therapies was evaluated in both metastatic hormone-sensitive (mHSPC) and castration-resistant prostate cancer (mCRPC). In patients with mCRPC, BRCA1/2 or ATM mutations predicted response to ARPIs (LOE IB) and PARPIs (LOE IIB), while AR-V7 transcripts or AR-V7 protein levels in circulating tumor cells (CTCs) predicted response to ARPIs and taxanes (LOE IB). CTC quantification predicted response to cabazitaxel, abiraterone, and radium-223 (LOE IIB), while TP53 alterations predicted response to 177Lu prostate-specific membrane antigen radioligand treatment (LOE IIB). AR copy number in circulating tumor DNA before the first treatment line and before subsequent lines predicted response to docetaxel, cabazitaxel, and ARPIs (LOE IIB). In mHSPC, DNA damage in lymphocytes was predictive of the response to radium-223 (LOE IIB).

CONCLUSIONS AND CLINICAL IMPLICATIONS

BRCA1/2, ATM, and AR alterations detected in liquid biopsies may help clinicians in management of patients with mPCa. The other circulating biomarkers did not reach the LOE required for routine clinical use and should be validated in prospective independent studies.

PATIENT SUMMARY

We reviewed studies assessing the value of biomarkers in blood or urine for management of metastatic prostate cancer. The evidence indicates that some biomarkers could help in selecting patients eligible for specific treatments.

Pre-treatment 68 Ga-PSMA-11 PET/CT Prognostic Value in Predicting Response to 177Lu-PSMA-I&T Therapy and Patient Survival

PURPOSE

To assess the prognostic value of pre-treatment [68Ga]Ga-PSMA-11 PET/CT and other baseline clinical characteristics in predicting prostate cancer (PCa) patients response to [177Lu]Lu-PSMA (PSMA-I&T), as well as patient survival.

PROCEDURES

In this retrospective study, 81 patients who received [177Lu]Lu-PSMA-I&T between October 2018 and January 2023 were reviewed. Eligible patients had metastatic castration-resistant PCa, underwent pre-treatment [68Ga]Ga-PSMA-11 PET/CT, and had serum prostate-specific antigen (PSA) levels available. On PET/CT images, SUVmax, SULmax, SUVpeak, and SULpeak of the most-avid tumoral lesion, as well as SUVmean of the parotid gland (P-SUVmean) and liver (L-SUVmean), were measured. Also, whole-body PSMA tumour volume (PSMA-TV) and total lesion PSMA (TL-PSMA) were calculated. To interpret treatment response after [177Lu]Lu-PSMA-I&T, a composite of PSA values and [68Ga]Ga-PSMA-11 PET/CT findings were considered. The outcomes were dichotomised into progressive versus controlled (stable disease or partial response) disease. Then, the association of baseline parameters with patient response was evaluated. Also, survival analyses were performed to assess baseline parameters in predicting overall survival.

RESULTS

Sixty patients (age:73 ± 8, PSA:185 ± 371) were included. Patients received at least one cycle of [177Lu]Lu-PSMA therapy (median = 4). Overall, half of the patients showed disease progression. In the progressive versus controlled disease evaluation, the highest SULmax, as well as SUVmax and SULmax to both backgrounds (L-SUVmean and P-SUVmean), were significantly correlated with the outcome (p-values < 0.05). In the multivariate analysis, only SULmax to the L-SUVmean remained significant (p-value = 0.038). The best cut-off was 8 (AUC = 0.71). With a median follow-up of 360 days, 11 mortal events were documented. In the multivariate survival analysis, only SULmax to P-SUVmean (cut-off = 2.4; p-value = 0.043) retained significance (hazard ratio = 4.0).

CONCLUSIONS

A greater level of PSMA uptake, specifically higher tumour-to-background uptake in the hottest lesion, may hold substantial prognostic significance, considering both [177Lu]Lu-PSMA-I&T response and patient survival. These ratios may have the potential to be used for PCa patient selection for radioligand therapy.

Analysing the tumor transcriptome of prostate cancer to predict efficacy of Lu-PSMA therapy

RATIONALE

177Lu-PSMA ([177Lu]Lutetium-PSMA-617) therapy is an effective treatment option for patients with prostate specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer, but still shows a non-responder rate of approximately 30%. Combination regimes of programmed death-ligand 1 (PD-L1) inhibition and concomitant 177Lu-PSMA therapy have been proposed to increase the response rate. However, the interplay of immune landscape and 177Lu-PSMA therapy efficacy is poorly understood.

METHODS

Between March 2018 and December 2021, a total of 168 patients were referred to 177Lu-PSMA therapy in our department and received a mean total dose of 21.9 GBq (three cycles in mean). All patients received baseline PSMA positron emission tomography to assess the PSMA uptake. The histopathological specimen of the primary prostate tumor was available with sufficient RNA passing quality control steps for genomic analysis in n=23 patients. In this subset of patients, tumor RNA transcriptomic analyses assessed 74 immune-related features in total, out of which n=24 signatures were not co-correlated and investigated further for outcome prognostication.

RESULTS

In the subset of patients who received 177Lu-PSMA therapy, PD-L1 was not significantly associated with OS (HR per SD change (95% CI) 0.74 (0.42 to 1.30); SD: 0.18; p=0.29). In contrast, PD-L2 signature was positively associated with longer OS (HR per SD change 0.46 (95% CI 0.29 to 0.74); SD: 0.24; p=0.001; median OS 17.2 vs 5.7 months in higher vs lower PD-L2 patients). In addition, PD-L2 signature correlated with PSA-response (ϱ=-0.46; p=0.04). The PD-L2 signature association with OS was significantly moderated by L-Lactatdehydrogenase (LDH) levels (Cox model interaction p=0.01).

CONCLUSION

Higher PD-L2 signature might be associated with a better response to 177Lu-PSMA therapy and warrants further studies investigating additional immunotherapy. In contrast, PD-L1 was not associated with outcome. The protective effect of PD-L2 signature might be present only in men with lower LDH levels.

Tumoral Ki67 and PSMA Expression in Fresh Pre-PSMA-RLT Biopsies and Its Relation With PSMA-PET Imaging and Outcomes of PSMA-RLT in Patients With mCRPC

INTRODUCTION

Prostate specific membrane antigen (PSMA) directed radioligand therapy (RLT) is a novel therapy for metastatic castration-resistant prostate cancer (mCRPC) patients. However, it is still poorly understood why approximately 40% of the patients does not respond to PSMA-RLT. The aims of this study were to evaluate the pretreatment PSMA expression on immunohistochemistry (IHC) and PSMA uptake on PET/CT imaging in mCRPC patients who underwent PSMA-RLT. We correlated these parameters and a cell proliferation marker (Ki67) to the therapeutic efficacy of PSMA-RLT.

PATIENTS AND METHODS

In this retrospective study, mCRPC patients who underwent PSMA-RLT were analyzed. Patients biopsies were scored for immunohistochemical Ki67 expression, PSMA staining intensity and percentage of cells with PSMA expression. Moreover, the PSMA tracer uptake of the tumor lesion(s) and healthy organs on PET/CT imaging was assessed. The primary outcome was to evaluate the association between histological PSMA protein expression of tumor in pre-PSMA-RLT biopsies and the PSMA uptake on PSMA PET/CT imaging of the biopsied lesion. Secondary outcomes were to assess the relationship between PSMA expression and Ki67 on IHC and the progression free survival (PFS) and overall survival (OS) following PSMA-RLT.

RESULTS

In total, 22 mCRPC patients were included in this study. Nineteen (86%) patients showed a high and homogenous PSMA expression of >80% on IHC. Three (14%) patients had low PSMA expression on IHC. Although there was limited PSMA uptake on PET/CT imaging, these 3 patients had lower PSMA uptake on PET/CT imaging compared to the patients with high PSMA expression on IHC. Yet, no correlation was found between PSMA uptake on PET/CT imaging and PSMA expression on IHC (SUVmax: R2 = 0.046 and SUVavg: R2 = 0.036). The 3 patients had a shorter PFS compared to the patients with high PSMA expression on IHC (HR: 4.76, 95% CI: 1.14-19.99; P = .033). Patients with low Ki67 expression had a longer PFS and OS compared to patients with a high Ki67 expression (HR: 0.40, 95% CI: 0.15-1.06; P = .013) CONCLUSION: The PSMA uptake on PSMA-PET/CT generally followed the PSMA expression on IHC. However, heterogeneity may be missed on PSMA-PET/CT. Immunohistochemical PSMA and Ki67 expression in fresh tumor biopsies, may contribute to predict treatment efficacy of PSMA-RLT in mCRPC patients. This needs to be further explored in prospective cohorts.

SUVmean on baseline [18F]PSMA-1007 PET and clinical parameters are associated with survival in prostate cancer patients scheduled for [177Lu]Lu-PSMA I&T

BACKGROUND

Quantification of [68 Ga]-labeled PSMA PET predicts response in patients with prostate cancer (PC) who undergo PSMA-targeted radioligand therapy (RLT). Given the increasing use [18F]-labeled radiotracers, we aimed to determine whether the uptake derived from [18F]PSMA-1007 PET can also identify responders and to assess its prognostic value relative to established clinical parameters.

METHODS

We retrospectively analyzed 103 patients with metastatic, castration-resistant PC who were treated with [177Lu]Lu-PSMA I&T. We calculated SUVmean, SUVmax, PSMA-avid tumor volume (TV), and total lesion PSMA (defined as PSMA-TV*SUVmean) on pre-therapeutic [18F]PSMA-1007 PET. Laboratory values for hemoglobin, C-reactive protein (CRP), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alkaline phosphatase (AP) were also collected prior to RLT. We performed univariable Cox regression followed by multivariable and Kaplan-Meier analyses with overall survival (OS) serving as endpoint. Last, we also computed a risk factor (RF) model including all items reaching significance on multivariable analysis to determine whether an increasing number of RFs can improve risk stratification.

RESULTS

A total of 48 patients died and median OS was 16 months. On univariable Cox regression, SUVmean, CRP, LDH, hemoglobin, and the presence of liver metastases were significantly associated with OS. On multivariable Cox regression, the following significant prognostic factors for OS were identified: SUVmean (per unit, HR, 0.91; P = 0.04), the presence of liver metastases (HR, 2.37; P = 0.03), CRP (per mg/dl, HR, 1.13; P = 0.003), and hemoglobin (per g/dl, HR, 0.76; P < 0.01). Kaplan-Meier analysis showed significant separation between patients with a SUVmean below or above a median SUVmean of 9.4 (9 vs 19 months, HR 0.57; P = 0.03). Of note, patients with only one RF (median OS not reached) showed longest survival compared to patients with two (11 months; HR 2.43 95% CI 1.07-5.49, P = 0.02) or more than two RFs (7 months; HR 3.37 95% CI 1.62-7.03, P < 0.001).

CONCLUSION

A lower SUVmean derived from [18F]PSMA-1007, higher CRP, lower hemoglobin, and the presence of liver metastases are associated with reduced OS in patients undergoing RLT. An early RF model also demonstrated that an increasing number of those factors is linked to worse outcome, thereby emphasizing the importance of clinical and imaging parameters for adequate risk stratification.

PSMA PET Tumor-to-Salivary Gland Ratio to Predict Response to [177Lu]PSMA Radioligand Therapy: An International Multicenter Retrospective Study

Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy can improve the outcome of patients with advanced metastatic castration-resistant prostate cancer, but patients do not respond uniformly. We hypothesized that using the salivary glands as a reference organ can enable selective patient stratification. We aimed to establish a PSMA PET tumor-to-salivary gland ratio (PSG score) to predict outcomes after [177Lu]PSMA. Methods: In total, 237 men with metastatic castration-resistant prostate cancer treated with [177Lu]PSMA were included. A quantitative PSG (qPSG) score (SUVmean ratio of whole-body tumor to parotid glands) was semiautomatically calculated on baseline [68Ga]PSMA-11 PET images. Patients were divided into 3 groups: high (qPSG > 1.5), intermediate (qPSG = 0.5-1.5), and low (qPSG < 0.5) scores. Ten readers interpreted the 3-dimensional maximum-intensity-projection baseline [68Ga]PSMA-11 PET images and classified patients into 3 groups based on visual PSG (vPSG) score: high (most of the lesions showed higher uptake than the parotid glands) intermediate (neither low nor high), and low (most of the lesions showed lower uptake than the parotid glands). Outcome data included a more than 50% prostate-specific antigen decline, prostate-specific antigen (PSA) progression-free survival, and overall survival (OS). Results: Of the 237 patients, the numbers in the high, intermediate, and low groups were 56 (23.6%), 163 (68.8%), and 18 (7.6%), respectively, for qPSG score and 106 (44.7%), 96 (40.5%), and 35 (14.8%), respectively, for vPSG score. The interreader reproducibility of the vPSG score was substantial (Fleiss weighted κ, 0.68). The more than 50% prostate-specific antigen decline was better in patients with a higher PSG score (high vs. intermediate vs. low, 69.6% vs. 38.7% vs. 16.7%, respectively, for qPSG [P < 0.001] and 63.2% vs 33.3% vs 16.1%, respectively, for vPSG [P < 0.001]). The median PSA progression-free survival of the high, intermediate, and low groups by qPSG score was 7.2, 4.0, and 1.9 mo (P < 0.001), respectively, by qPSG score and 6.7, 3.8, and 1.9 mo (P < 0.001), respectively, by vPSG score. The median OS of the high, intermediate, and low groups was 15.0, 11.2, and 13.9 mo (P = 0.017), respectively, by qPSG score and 14.3, 9.6, and 12.9 mo (P = 0.018), respectively, by vPSG score. Conclusion: The PSG score was prognostic for PSA response and OS after [177Lu]PSMA. The visual PSG score assessed on 3-dimensional maximum-intensity-projection PET images yielded substantial reproducibility and comparable prognostic value to the quantitative score.

Joint EANM/SNMMI procedure guideline for the use of 177Lu-labeled PSMA-targeted radioligand-therapy (177Lu-PSMA-RLT)

Prostate-specific membrane antigen (PSMA) is expressed by the majority of clinically significant prostate adenocarcinomas, and patients with target-positive disease can easily be identified by PSMA PET imaging. Promising results with PSMA-targeted radiopharmaceutical therapy have already been obtained in early-phase studies using various combinations of targeting molecules and radiolabels. Definitive evidence of the safety and efficacy of [177Lu]Lu-PSMA-617 in combination with standard-of-care has been demonstrated in patients with metastatic castration-resistant prostate cancer, whose disease had progressed after or during at least one taxane regimen and at least one novel androgen-axis drug. Preliminary data suggest that 177Lu-PSMA-radioligand therapy (RLT) also has high potential in additional clinical situations. Hence, the radiopharmaceuticals [177Lu]Lu-PSMA-617 and [177Lu]Lu-PSMA-I&T are currently being evaluated in ongoing phase 3 trials. The purpose of this guideline is to assist nuclear medicine personnel, to select patients with highest potential to benefit from 177Lu-PSMA-RLT, to perform the procedure in accordance with current best practice, and to prepare for possible side effects and their clinical management. We also provide expert advice, to identify those clinical situations which may justify the off-label use of [177Lu]Lu-PSMA-617 or other emerging ligands on an individual patient basis.

Elevated Body Mass Index Is Associated with Improved Overall Survival in Castration-Resistant Prostate Cancer Patients Undergoing Prostate-Specific Membrane Antigen-Directed Radioligand Therapy

In patients with prostate cancer scheduled for systemic treatment, being overweight is linked to prolonged overall survival (OS), whereas sarcopenia is associated with shorter OS. We investigated fat-related and body composition parameters in patients undergoing prostate-specific membrane antigen (PSMA)-directed radioligand therapy (RLT) to assess their predictive value for OS. Methods: Body mass index (BMI, in kg/m²) and CT-derived body composition parameters (total, subcutaneous, visceral fat area, and psoas muscle area at the L3-L4 level) were determined for 171 patients scheduled for PSMA-directed RLT. After normalization for stature, the psoas muscle index was used to define sarcopenia. Outcome analysis was performed using Kaplan-Meier curves and Cox regression including fat-related and other clinical parameters (Gleason score, C-reactive protein [CRP], lactate dehydrogenase [LDH], hemoglobin, and prostate-specific antigen levels). The Harrell C-index was used for goodness-of-fit analysis. Results: Sixty-five patients (38%) had sarcopenia, and 98 patients (57.3%) had increased BMI. Relative to the 8-mo OS in normal-weight men (BMI < 25), overweight men (25 ≥ BMI > 30) and obese men (BMI ≥ 30) achieved a longer OS of 14 mo (hazard ratio [HR], 0.63; 95% CI, 0.40-0.99; P = 0.03) and 13 mo (HR, 0.47; 95% CI, 0.29-0.77; P = 0.004), respectively. Sarcopenia showed no impact on OS (11 vs. 12 mo; HR, 1.4; 95% CI, 0.91-2.1; P = 0.09). Most of the body composition parameters were tightly linked to OS on univariable analyses, with the highest C-index for BMI. In multivariable analysis, a higher BMI (HR, 0.91; 95% CI, 0.86-0.97; P = 0.006), lower CRP (HR, 1.09; 95% CI, 1.03-1.14; P < 0.001), lower LDH (HR, 1.08; 95% CI, 1.03-1.14; P < 0.001), and longer interval between initial diagnosis and RLT (HR, 0.95; 95% CI, 0.91-0.99; P = 0.02) were significant predictors of OS. Conclusion: Increased fat reserves assessed by BMI, CRP, LDH, and interval between initial diagnosis and RLT, but not CT-derived body composition parameters, were relevant predictors for OS. As BMI can be altered, future research should investigate whether a high-calorie diet before or during PSMA RLT may improve OS.

Determinants of outcome following PSMA-based radioligand therapy and mechanisms of resistance in patients with metastatic castration-resistant prostate cancer

[177Lu]Lu-PSMA has recently been approved for use in the post-taxane, post-novel hormonal-agent setting in patients with metastatic castration-resistant prostate cancer. As a beta-emitting radioligand targeting prostate-specific membrane antigen (PSMA), it delivers radiation to cells expressing PSMA on their surface. In pivotal clinical trials, patients were selected for this treatment based on positron emission tomography (PET)/CT imaging, requiring PSMA-avid disease with no evidence of discordant disease on 2-[18F]fluoro-2-deoxy-D-glucose PET/CT or contrast CT scan. Despite exhibiting an optimal imaging phenotype, the response for many patients is not durable, and a minority do not respond to [177Lu]Lu-PSMA at all. Disease progression is inevitable even for those who achieve an exceptional initial response. Reasons for both primary and acquired resistance are largely unknown; however, they are likely due to the presence of underlying PSMA-negative disease not identified on imaging, molecular factors conferring radioresistance, and inadequate delivery of lethal radiation, particularly to sites of micrometastatic disease. Biomarkers are urgently needed to optimize patient selection for treatment with [177Lu]Lu-PSMA by identifying those who are most and least likely to respond. Retrospective data support using several prognostic and predictive baseline patient- and disease-related parameters; however, robust prospective data is required before these can be translated into widespread use. Further, early on-treatment clinical parameters (in addition to serial prostate-specific antigen [PSA] levels and conventional restaging imaging) may serve as surrogates for predicting treatment response. With little known about the efficacy of treatments given after [177Lu]Lu-PSMA, optimal treatment sequencing is paramount, and biomarker-driven patient selection will hopefully improve treatment and survival outcomes.

PSMA-heterogeneity in metastatic castration-resistant prostate cancer: Circulating tumor cells, metastatic tumor burden, and response to targeted radioligand therapy

BACKGROUND

We explored the interrelation between prostate-specific membrane antigen (PSMA) expression on circulating tumor cells (CTCs) and that of solid metastatic lesions as determined by whole-body PSMA-targeted positron emission tomography (PET) to refine the prediction of response to subsequent PSMA-targeted radioligand therapy (RLT).

METHODS

A prospective study was performed in 20 patients with advanced mCRPC. Of these, 16 underwent subsequent RLT with [¹⁷⁷ Lu]Lu-PSMA-617 at a dose of 7.4 GBq every 6-8 weeks. PSMA expression on CTCs using the CellSearch system was compared to clinical and serological results, and to marker expression in targeted imaging and available histological sections of prostatectomy specimens (19% of RLT patients). Clinical outcome was obtained after two cycles of RLT.

RESULTS

Marked heterogeneity of PSMA expression was observed already at first diagnosis in available histological specimens. Targeted whole-body imaging also showed heterogeneous inter- and intra-patient PSMA expression between metastases. Heterogeneity of CTC PSMA expression was partially paralleled by heterogeneity of whole-body tumor burden PSMA expression. Twenty percent of CTC samples showed no PSMA expression, despite unequivocal PSMA expression of solid metastases at PET. A high fraction of PSMA-negative CTCs emerged as the sole predictor of poor RLT response (odds ratio [OR]: 0.9379 [95% confidence interval, CI, 0.8558-0.9902]; p = 0.0160), and was prognostic for both shorter progression-free survival (OR: 1.236 [95% CI, 1.035-2.587]; p = 0.0043) and overall survival (OR: 1.056 [95% CI, 1.008-1.141]; p = 0.0182).

CONCLUSION

This proof-of-principle study suggests that liquid biopsy for CTC PSMA expression is complementary to PET for individual PSMA phenotyping of mCRPC.

PSMA PET/CT: joint EANM procedure guideline/SNMMI procedure standard for prostate cancer imaging 2.0

Here we aim to provide updated guidance and standards for the indication, acquisition, and interpretation of PSMA PET/CT for prostate cancer imaging. Procedures and characteristics are reported for a variety of available PSMA small radioligands. Different scenarios for the clinical use of PSMA-ligand PET/CT are discussed. This document provides clinicians and technicians with the best available evidence, to support the implementation of PSMA PET/CT imaging in research and routine practice.

Second Version of the Prostate Cancer Molecular Imaging Standardized Evaluation Framework Including Response Evaluation for Clinical Trials (PROMISE V2)

CONTEXT

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) is emerging to become a reference imaging tool for the staging and restaging of patients with prostate cancer for both clinical routine and trials. The prostate cancer molecular imaging standardized evaluation (PROMISE) criteria have been proposed as a framework for whole-body staging (molecular imaging TNM staging, denoted miTNM staging) to describe the prostate cancer disease extent on PSMA-PET.

OBJECTIVE

To create a comprehensive and integrated framework for PSMA-PET image interpretation and reporting.

EVIDENCE ACQUISITION

We propose the PROMISE V2 framework, which integrates an updated miTNM system, improved assessment of local disease, and a slightly modified PSMA-expression score for clinical routine. We have added a response monitoring framework defining qualitative and quantitative parameters to be recorded for a longitudinal assessment in clinical trials.

EVIDENCE SYNTHESIS

We provide a comprehensive literature review on the current use of the PROMISE framework in clinical research and prospective trials. PROMISE variables demonstrate a clear association with survival. PSMA expression assessed by the PSMA-expression score was used in several trials, and a low PSMA-expression score is a negative prognosticator of overall survival after ¹⁷⁷Lu-PSMA radioligand therapy. The proposed imaging parameters recorded for response assessment in clinical trials can be utilized to determine response according to PSMA-PET progression (PPP) or Response Evaluation Criteria in PSMA-PET/Computed Tomography (RECIP) frameworks, but also future response criteria.

CONCLUSIONS

PROMISE V2 offers standardized reporting of disease extent for clinical routine and research. Parameters recorded within clinical trials facilitate objective response assessment.

PATIENT SUMMARY

Prostate-specific membrane antigen (PSMA) targeting positron emission tomography (PET) has become a standard imaging examination for prostate cancer. We propose a comprehensive framework for the analysis and reporting of PSMA-PET findings that will improve the communication between imaging experts and uro-oncologists.

Prognostic factors of overall and prostate-specific antigen-progression-free survival in metastatic castration-resistant prostate cancer patients treated with 177 Lu-PSMA-617. A single-center prospective observational study

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) is characterized by heterogeneity among patients as well as therapy responses due to diverse genetic, epigenetic differences, and resistance mechanisms. At this stage of the disease, therapy modalities should be individualized in light of the patients' clinical state, symptoms, and genetic characteristics. In this prospective study, we aimed to evaluate the outcome of patients with mCRPC treated with ¹⁷⁷ Lutetium labeled PSMA-617 therapy (PSMA-RLT), as well as baseline and therapy-related parameters associated with survival.

METHODS

This prospective study included 52 patients who received two to six cycles of PSMA-RLT. Primary endpoints were overall survival (OS) and prostate-specific antigen (PSA)-progression-free survival (PFS). ¹⁸ F-Fluorodeoxyglucose (FDG) and ⁶⁸ Ga-PSMA (PSMA) Positron Emission Tomography/Computer Tomography (PET/CT) scans were performed for a comprehensive assessment of tumor burden and heterogeneity. Biochemical, imaging, clinical, and therapy-related parameters were analyzed with the Kaplan-Meier, log-rank, and Cox regression analyses to predict OS and PFS.

RESULTS

Median OS and PSA-PFS were 17.7 (95% confidence interval [CI]: 15.2-20.2) and 6.6 months (95% CI: 4.5-8.8), respectively. Primary resistance to PSMA-RLT (hazard ratio [HR]: 12.57, 95% CI: 2.4-65.2, p: 0.003), <30% PSA response rate after first cycle of PSMA-RLT (HR: 1.016, 95% CI: 1.006-1.03, p: 0.003), FDG > PSMA disease (HR: 4.9, 95% CI: 1.19-20.62, p: 0.03), PSA doubling time (PSA DT) of ≤2.4 months (HR: 15.7, 95% CI: 3.7-66.4, p: <0.0001), and low hemoglobin levels (HR: 0.59, 95% CI: 0.41-0.83, p: 0.003) were correlated with poor OS in the multivariate analysis. Bone scintigraphy >  PSMA disease (HR: 5.6; 95% CI: 1.8-17, p: 0.002) and high C-reactive protein (HR: 1.4, 95% CI: 1.1-1.7, p: 0.001) were significant predictive biomarkers for PFS in the multivariate analysis.

CONCLUSION

PSA response rate and pattern to PSMA-RLT are the most important predictors of survival in patients receiving PSMA-RLT. Being a strong predictive biomarker, combined FDG and PSMA PET can be helpful for the decision of PSMA-RLT eligibility.

Chromogranin A: a useful biomarker in castration-resistant prostate cancer

PURPOSE

The natural history of prostate cancer (PC) almost always evolves to castration-resistant prostate cancer (CRPC) status, sometimes comprising pure or mixed neuroendocrine prostate cancers (NEPC) differentiation. In CRPC, monitoring using only prostate-specific antigen (PSA) is not optimal since neuroendocrine differentiated cells do not secrete PSA. Thus, monitoring with PSA and chromogranin A (CgA) may be useful. This review aims to evaluate evidence for the usefulness of CgA assessments during the monitoring of prostate cancer.

METHOD

This review was based on three recent meta-analysis concerning CgA and prostate cancer. Further data were obtained from PubMed and Embase databases by searches using keywords, including chromogranin A and prostate cancer.

RESULTS

CgA levels remain largely unchanged during the early PC evolution. The development of NEPC is characterised by lower PSA secretion and increased CgA secretion. Data supporting the prognostic value of high CgA baseline levels for survival are contrasting and scarce. However, increasing CgA levels early during treatment of metastatic (m)CRPC suggests resistance to treatment and predicts shorter survival, particularly in men with high baseline levels of CgA levels. In men with mCRPC, the first-line chemotherapy may be more appropriate than other agents when baseline CgA levels are high. Also, increasing CgA levels during treatment may indicate disease progression and may warrant a change of therapy.

CONCLUSION

CgA monitoring at baseline and regularly during mCRPC management may be useful for monitoring disease evolution. An increased CgA baseline levels and increasing CgA levels may assist physicians with choosing and modifying therapy.

Evaluation of Tumor Burden Response to Single-cycle of Lu-177 PSMA Treatment with Whole Body Scintigraphic Planar Images in Prostate Cancer Patients

The aim of this study; evaluation of treatment response and survival with post-therapy images in patients who received one cycle of Lu-177 PSMA I&T treatment.

Clinical Applications of PSMA PET Examination in Patients with Prostate Cancer

Simple Summary

The prostate specific membrane antigens, abbreviated as PSMAs, are type II membrane proteins that are highly ex-pressed on the surface of malignant prostate tissue in prostate cancer (PCa), particularly in aggressive, andro-gen-deprived, metastatic, and hormone-refractory PCa. Today, radionuclides that bind to these PSMA peptides are widely available for diagnostic and therapeutic purposes to specifically image and target prostate tumor cells at molec-ular level. In this descriptive review, we aimed to emphasize the usefulness of PSMA positron emission tomography (PET) examination in the management of patients with various stages of PCa. In addition, we outlined the main pitfalls and limitations of this scan to avoid misinterpretation of the results and to improve the decision making process in rela-tion to the patient’s further treatment. We concluded that PSMA PET examination in primary PCa patients has an es-sential role in the high-risk group. It is the new imaging standard in patients with in biochemical recurrence PCa and plays an important role in treatment decision. Furthermore, PSMA PET scan is a gold standard for the evaluation of PSMA targeted therapies in patients having progress of the disease. Future prospective studies, particularly on the im-pact of PSMA PET on therapy stratification, may further strengthen the role of PSMA in the treatment of PCa patients.

Abstract

With the progressive aging of the population in industrially developed countries, as well as advances in diagnostic and biopsy techniques and improvements in patient awareness, the incidence of prostate cancer (PCa) is continuously increasing worldwide. Therefore, PCa is currently considered as the second leading cause of tumor-related death. Early detection of the tumor and its metastasis is essential, as the rate of disease recurrence is high and occurs in 27% to 53% of all patients who underwent curative therapy with radical prostatectomy or local radiotherapy. In this regard, the prostate specific membrane antigens, abbreviated as PSMAs, are type II membrane proteins that are highly expressed on the surface of malignant prostate tissue in PCa, particularly in aggressive, androgen-deprived, metastatic, and hormone-refractory PCa, and they are inversely associated with the androgen level. Up to 95% of adenocarcinomas of the prostate express PSMA receptors on their surface. Today, radionuclides that bind to these PSMA peptides are widely accepted for diagnostic and therapeutic purposes to specifically image and target prostate tumor cells at the molecular level, a process referred to as targeted theranostics. Numerous studies have demonstrated that the integration of these peptides into diagnostic and therapeutic procedures plays a critical role in the primary staging and treatment decisions of especially high-risk PCa, expands therapeutic options for patients with advanced stage of prostate tumor, and prolongs patients’ survival rate. In this review article, we intend to briefly spotlight the latest clinical utilization of the PSMA-targeted radioligand PET imaging modality in patients with different stages of PCa. Furthermore, limitations and pitfalls of this diagnostic technique are presented.

Outcome of 177 Lu-PSMA Radionuclide Treatment in Advanced Prostate Cancer and Its Association With Clinical Parameters : A Single-Center Experience

PURPOSE

This study was set out to analyze the efficacy and safety of 177 Lu-PSMA-617 (LuPSMA) treatment in metastatic castration-resistant prostate cancer (mCRPC) patients.

PATIENTS AND METHODS

Progressive mCRPC patients who received at least 1 cycle of LuPSMA therapy were evaluated retrospectively. Demographic, clinic, and histopathological data were documented. Treatment efficacy was determined based on biochemical response criteria (Prostate Cancer Clinical Trial Working Group 3), and toxicity rates were defined based on CTCAE v4.03. The prognostic significance of laboratory/clinical data and 68 Ga-PSMA PET/CT quantitative results were analyzed using SPSS Version 24.0.

RESULTS

One hundred patients (median prostate-specific antigen [PSA] level, 75.7 ng/mL) who met the eligibility criteria were identified. The median number of cycles received per patient was 3 (range, 1-9). After the first cycles of LuPSMA, biochemical partial response, biochemical stable disease, and biochemical progressive disease were observed in 31%, 36%, and 33% of patients, respectively. Any PSA decline was determined in 60% of patients. After the fourth cycle of treatment, biochemical partial response, biochemical stable disease, and biochemical progressive disease were defined in 48%, 26%, and 26% of patients, respectively. The median overall survival (OS) from the first cycle of LuPSMA was 14 months. Patients who had any PSA response after the first cycle had significantly longer OS than nonresponders (median OS: 17 vs 9 months; P ≤ 0.001). Total PSMA-derived tumor volume ( P = 0.004), total PSMA activity per lesion ( P = 0.01), PSA ( P = 0.007), alkaline phosphatase ( P = 0.002), lactate dehydrogenase ( P < 0.001), and hemoglobin ( P < 0.001) were significant prognostic factors for OS in univariate Cox regression analysis.

CONCLUSIONS

LuPSMA therapy is a favorable treatment for mCRPC with remarkable therapeutic efficacy and low toxicity rates, even in progressive disease under standard therapies. Baseline PSMA-based tumor burden, PSA, alkaline phosphatase, lactate dehydrogenase, and hemoglobin were significant predictors of OS and can be useful for selection of the best candidate for LuPSMA therapy.

Pre- and intratherapeutic predictors of overall survival in patients with advanced metastasized castration-resistant prostate cancer receiving Lu-177-PSMA-617 radioligand therapy

BACKGROUND

Systemic Lutetium-177 prostate-specific membrane antigen-617 radioligand therapy (Lu-177-PSMA-617-RLT) is a novel treatment approach in patients suffering from metastasized castration-resistant prostate cancer. Nonetheless, a therapeutic response may fail to appear in a proportion of patients. This study aims to identify routinely obtainable pre- and intratherapeutic parameters to allow a prediction of overall survival in patients receiving Lu-177-PSMA-617 radioligand therapy.

METHODS

Between January 2015 and December 2020 52 patients treated with a total of 146 cycles Lu-177-PSMA-617-RLT were retrospectively analysed in a single-center trial. The median overall survival time (OS) was compared to pre-therapeutic serological parameters, the extend of metastatic spread and previously performed therapies using Kaplan-Meier estimators and multivariate Cox-regression. Bonferroni-Holm correction was performed on all statistical tests.

RESULTS

The median OS of all patients was 55.6 weeks. Multivariate Cox-regression revealed significant lower survival for decreased pretherapeutic hemoglobin levels (HR 0.698 per g/dl; 95%-CI 0.560-0.872; p = 0.001), increased lactate dehydrogenase (LDH) levels (HR 1.073 per 25 U/l; 95%-CI 1.024-1.125; p = 0.003) and the presence of hepatic metastasis (HR 6.981; 95%-CI 2.583-18.863; p < 0.001). Increased pretherapeutic c-reactive protein (CRP), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT) levels were also associated with a shorter survival. A prostate-specific antigen decline after one therapy cycle did not significantly correlate with an increased survival. No significant relations were observed between overall survival time and other serological parameters or previously performed therapies.

CONCLUSION

Pre-therapeutic hemoglobin and LDH levels, as well as the presence of hepatic metastasis are independent predictors of overall survival in patients receiving Lu-177-PSMA-617-RLT. CRP, ALP and GGT levels cloud be utilized as additional decision aids when a Lu-177-PSMA-617-RLT is intended. Trial Registration Not applicable (retrospective observational study).

Baseline clinical characteristics predict overall survival in patients undergoing radioligand therapy with [177Lu]Lu-PSMA I&T during long-term follow-up

Background

Radioligand therapy (RLT) with ¹⁷⁷Lu-labeled prostate-specific membrane antigen (PSMA) ligands is associated with prolonged overall survival (OS) in patients with advanced, metastatic castration-resistant prostate cancer (mCRPC). A substantial number of patients, however, are prone to treatment failure. We aimed to determine clinical baseline characteristics to predict OS in patients receiving [¹⁷⁷Lu]Lu-PSMA I&T RLT in a long-term follow-up.

Materials and methods

Ninety-two mCRPC patients treated with [¹⁷⁷Lu]Lu-PSMA I&T with a follow-up of at least 18 months were retrospectively identified. Multivariable Cox regression analyses were performed for various baseline characteristics, including laboratory values, Gleason score, age, prior therapies, and time interval between initial diagnosis and first treatment cycle (interval_{Diagnosis-RLT}, per 12 months). Cutoff values for significant predictors were determined using receiver operating characteristic (ROC) analysis. ROC-derived thresholds were then applied to Kaplan–Meier analyses.

Results

Baseline C-reactive protein (CRP; hazard ratio [HR], 1.10, 95% CI 1.02–1.18; P = 0.01), lactate dehydrogenase (LDH; HR, 1.07, 95% CI 1.01–1.11; P = 0.01), aspartate aminotransferase (AST; HR, 1.16, 95% CI 1.06–1.26; P = 0.001), and interval_{Diagnosis-RLT} (HR, 0.95, 95% CI 0.91–0.99; P = 0.02) were identified as independent prognostic factors for OS. The following respective ROC-based thresholds were determined: CRP, 0.98 mg/dl (area under the curve [AUC], 0.80); LDH, 276.5 U/l (AUC, 0.83); AST, 26.95 U/l (AUC, 0.73); and interval_{Diagnosis-RLT}, 43.5 months (AUC, 0.68; P < 0.01, respectively). Respective Kaplan–Meier analyses demonstrated a significantly longer median OS of patients with lower CRP, lower LDH, and lower AST, as well as prolonged interval_{Diagnosis-RLT} (P ≤ 0.01, respectively).

Conclusion

In mCRPC patients treated with [¹⁷⁷Lu]Lu-PSMA I&T, baseline CRP, LDH, AST, and time interval until RLT initiation (thereby reflecting a possible indicator for tumor aggressiveness) are independently associated with survival. Our findings are in line with previous findings on [¹⁷⁷Lu]Lu-PSMA-617, and we believe that these clinical baseline characteristics may support the nuclear medicine specialist to identify long-term survivors.

177 Lu-PSMA radioligand therapy effectiveness in metastatic castration-resistant prostate cancer: An updated systematic review and meta-analysis

BACKGROUND

An updated systematic review and meta-analysis of relevant studies to evaluate the effectiveness of prostate-specific membrane antigen (PSMA)-targeted endoradiotherapy/radioligand therapy (PRLT) in castration resistant prostate cancer (CRPC).

METHODS

A systematic search was performed in July 2020 using PubMed/Medline database to update our prior systematic review. The search was limited to papers published from 2019 to June 2020. A total of 472 papers were reviewed. The studied parameters included pooled proportion of patients showing any or ≥50% prostate-specific antigen (PSA) decline after PRLT. Survival effects of PRLT were assessed based on pooled hazard ratios (HRs) of the overall survival (OS) according to any PSA as well as ≥50% PSA decline after PRLT. Response to therapy based on ≥50% PSA decrease after PRLT versus controls was evaluated using Mantel-Haenszel random effect meta-analysis. All p values < 0.05 were considered as statistically significant.

RESULTS

A total of 45 publications were added to the prior 24 studies. 69 papers with total of 4157 patients were included for meta-analysis. Meta-analysis of the two recent randomized controlled trials showed that patients treated with ¹⁷⁷ Lu-PSMA 617 had a significantly higher response to therapy compared to controls based on ≥50% PSA decrease. Meta-analysis of the HRs of OS according to any PSA decline and ≥50% PSA decline showed survival prolongation after PRLT.

CONCLUSIONS

PRLT results in higher proportion of patients responding to therapy based on ≥50% PSA decline compared to controls. Any PSA decline and ≥50% PSA decline showed survival prolongation after PRLT.

ADVANCES IN KNOWLEDGE

This is the first meta-analysis to aggregate the recent randomized controlled trials of PRLT which shows CRPC patients had a higher response to therapy after PRLT compared to controls.

Predictors and Real-World Use of Prostate-Specific Radioligand Therapy: PSMA and Beyond

PSMA is a transmembrane protein that is markedly overexpressed in prostate cancer, making it an excellent target for imaging and treating patients with prostate cancer. Several small molecule inhibitors and antibodies of PSMA have been radiolabeled for use as therapeutic agents and are currently under clinical investigation. PSMA-based radionuclide therapy is a promising therapeutic option for men with metastatic prostate cancer. The phase II TheraP study demonstrated superior efficacy, lower side effects, and improved patient-reported outcomes compared with cabazitaxel. The phase III VISION study demonstrated that radionuclide therapy with β-emitter ¹⁷⁷Lu-PSMA-617 can prolong survival and improve quality of life when offered in addition to standard-of-care therapy in men with PSMA-positive metastatic castration-resistant prostate cancer whose disease had progressed with conventional treatments. Nevertheless, up to 30% of patients have inherent resistance to PSMA-based radionuclide therapy, and acquired resistance is inevitable. Hence, strategies to increase the efficacy of PSMA-based radionuclide therapy have been under clinical investigation. These include better patient selection; increased radiation damage delivery via dosimetry-based administered dose or use of α-emitters instead of β-emitters; or using combinatorial approaches to overcome radioresistance mechanisms (innate or acquired), such as with novel hormonal agents, PARP inhibitors, or immunotherapy.

177Lu-PSMA-I&T Radioligand Therapy for Treating Metastatic Castration-Resistant Prostate Cancer: A Single-Centre Study in East Asians

Purpose

There is increasing evidence for convincing efficacy and safety of ¹⁷⁷Lu-labled prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (PRLT) for metastatic castration-resistant prostate cancer (mCRPC). However, data are not available regarding the feasibility of ¹⁷⁷Lu-labled PSMA-targeted RLT in East Asians. The present study summarized the first experience with ¹⁷⁷Lu-PSMA-I&T therapy for mCRPC in China.

Methods

Forty consecutive patients with mCRPC were enrolled from December 2019 to September 2021. Eligible patients received ¹⁷⁷Lu-PSMA-I&T RLT at intervals of 8-12 weeks. Toxicity was assessed based on standardized physicians’ reports and the Common Toxicity Criteria for Adverse Events criteria. Response to PRLT was evaluated according to the changes of prostate specific antigen (PSA) response and imaging response. Quality of life (QOL), Karnofsky performance status (KPS) and pain (visual analogue scale, VAS) were also evaluated. The impacts of baseline parameters on the therapeutic effects were explored by univariate and multivariate logistic regression analyses.

Results

All patients underwent a total of 86 cycles of ¹⁷⁷Lu-PSMA-I&T (range: 1-5 cycles) with dosages of 3.70-14.43GBq per cycle, with a median of 8 months followed up. Six patients (15%) developed mild reversible xerostomia during follow-up, and 28 patients (70%) experienced grade 1-4 bone marrow dysfunction. Changes in PSA were assessed after therapy, accompanied by the partial response (PR) in 25 patients (62.5%), the stable disease (SD) in 5 patients (12.5%), and the progressive disease (PD) in 10 patients (25%), respectively. QOL, KPS (%) and VAS scores were improved significantly due to treatment (P<0.05). Overweight and elevated AST, ALP, and LDH were associated with poor outcomes.

Conclusions

¹⁷⁷Lu-PSMA-I&T achieves the favourable response and well tolerance in mCRPC, which associates with not only PSA decline but also with tumor remission including lymphadenopathy and bone metastasis. We also find that patients with overweight and high AST, ALP, and LDH should be cautious to undergo the PRLT. Large-cohort studies are warranted to confirm the initial findings and elucidate the survival benefit of the treatment.

Biomarkers to personalize treatment with 177Lu-PSMA-617 in men with metastatic castration-resistant prostate cancer - a state of the art review

Radioligand therapy with Lutetium-177 (177Lu)-Prostate-specific membrane antigen (PSMA) has shown to prolong survival in metastatic castration resistant prostate cancer (mCRPC). One of the major challenges for clinicians in the future is to select those patients who would benefit most from this therapy to position it in the treatment landscape of mCRPC. This, in turn, will lead to the delivery of personalized therapies. In this narrative review article we summarize recent studies investigating both predictive and prognostic clinical, imaging-based, and molecular biomarkers to predict treatment response to 177Lu-PSMA-617 radioligand therapy with the aim of identifying men who should be considered for this approach. Of note, the evidence on the role of biomarkers currently relies on small retrospective trials and their validation in larger prospective cohorts is necessary before these results can be translated in the clinical practice.

Prediction of early biochemical response after 177Lu-PSMA radioligand therapy with 68Ga-PSMA PET, a different perspective with quantitative parameters

OBJECTIVE

In this study, our aim was to evaluate the relationship of the quantitative data obtained from pretreatment 68Ga prostate-specific membrane antigen (PSMA) PET-computerized tomography (PET/CT) with treatment response of the patients with the diagnosis of metastatic castrationresistant prostate cancer (mCRPC) who received 177Lu-PSMA radioligand therapy (RLT).

METHODS

The patients who were given three or four cycles of 177Lu-PSMA RLT between January 2016 and June 2018 were evaluated retrospectively. Volumetric data; PSMA tumor volume (TV) and total lesion (TL) PSMA, were obtained from 68Ga-PSMA PET/CT for whole (PSMA-TVT and TL-PSMAT). The distance between the two furthest lesions (Dmax) was calculated. Posttreatment early prostate-specific antigen (PSA) values on the fourteenth day after treatment were obtained. According to the PSA responses, the patients were divided into two groups as progressed and nonprogressed. In univariate analysis, the relationship of PET quantitative data with biochemical response groups was evaluated with Mann-Whitney U test. Logistic regression was used in multivariate analysis.

RESULTS

A total of 38 patients were included in the study. In univariate analysis, Dmax, PSMA-TVT and TL-PSMAT values were obtained at lower levels in the progressed group. In multivariate analysis, only Dmax was found to be a prognostic factor in predicting early biochemical response.

CONCLUSION

Dmax is the most prognostic parameter in predicting the early biochemical response in patients with mCRPC; high total tumor volume and burden are also parameters that give us an idea about the response to treatment. The success rate will be higher if 177Lu-PSMA RLT treatment is planned for patients with higher tumor volume and spread.

Two Tumors, One Target: Preliminary Experience With 90Y-FAPI Therapy in a Patient With Metastasized Breast and Colorectal Cancer

ABSTRACT

We report a patient with breast cancer (BC) diagnosed in 2009 with metachronous lymph node, liver, and bone metastases. In 2017, colorectal cancer with peritoneal metastases was additionally diagnosed and treated with 8 cycles of capecitabine due to its antitumor activity against both malignancies. At progression of both diseases, FAPI PET/CT demonstrated positive tumor targeting in BC-related metastases and colorectal cancer-related metastases. The patient received an experimental therapy with 90Y-FAPI46. Although there was similar tracer uptake in the PET/CT, the radioligand therapy resulted in mixed response with disappearance of peritoneal metastases but minor efficacy treating the BC-related metastases.

Outcome of 177Lu-PSMA-617 Radioligand Therapy in Chemo-Refractory Patients with Metastatic Castration-Resistant Early-Onset Prostate Cancer

Simple Summary

The risk of prostate cancer development, the second most commonly occurring cancer in men overall, increases strongly with age. About 10% of patients, however, are diagnosed with early-onset prostate cancer (age at diagnosis: ≤55 years). This is considered to be a distinct clinical and pathological phenotype with a poor prognosis. Generally, prostate cancer cells express high quantities of prostate-specific membrane antigen (PSMA) on their surface. Radioligand therapy is a type of treatment, which, among other available agents, uses the beta-emitting radionuclide ¹⁷⁷Lutetium (¹⁷⁷Lu) and a PSMA-targeting ligand termed PSMA-617 for internal irradiation of metastatic prostate cancer cells. The aim of our retrospective study was to assess the efficacy and safety of radioligand therapy with ¹⁷⁷Lu-PSMA-617 in early-onset metastasized castration-resistant prostate cancer patients refractory to chemotherapy. Special emphasis was placed on the patients’ response to the treatment and survival. The study provides support for the expected shorter survival compared to heterogenous patient groups.

Abstract

The aim of this retrospective study was to assess the outcome of patients with metastasized castration-resistant early-onset prostate cancer refractory to chemotherapy receiving radioligand therapy with ¹⁷⁷Lutetium-PSMA-617 (LuPSMA-RLT). Twenty-five patients of ≤55 years of age at prostate cancer diagnosis, treated with a median of four (IQR 2–6) cycles (mean of 7.7 ± 1.4 GBq per cycle) every 6–8 weeks, were analyzed. Survival outcome was calculated based on the Kaplan–Meier method. The median progression-free survival (PFS) was 3.8 months (95% CI 2.3–5.3), and overall survival (OS) was 8.5 months (95% CI 6.2–10.8). An initial PSA reduction (≥ 50%) was observed in 9/25 (36%) of patients without being significantly associated with OS (p = 0.601). PSA response (PSA decline ≥50% at 12 weeks) was observed in 12/25 (48%) of patients and significantly associated with longer OS (16.0 months, 95% CI 7.4–24.6 vs. 4.0 months, 95% CI 1.1–6.9, p = 0.002). Imaging-based response using ⁶⁸Ga-PSMA-11-PET/CT after two to three cycles was seen in 11/25 (44%). Additionally, responders had a significantly longer median PFS (8.7 months, 95% CI 1.3–16.1 vs. 1.9 months, 95% CI 1.7–2.2, p < 0.001) and OS (16.0 months, 95% CI 7.6–24.4 vs. 4.0 months, 95% CI 0.9–7.1; p = 0.002). Intra- or post-therapeutic toxicity was graded according to the CTCAE v5.0 criteria. Newly developing grade ≥ 3 anemia, leukopenia, and thrombocytopenia occurred in three (12%), one (4%), and three (12%) patients, respectively. One patient showed renal toxicity (grade ≥ 3) during follow-up. Pain palliation (>2 level VAS decline) was achieved in 9/14 (64%) and performance status improvement (ECOG level decline ≥ 1) in 8/17 (47%) of patients. Compared to previous reports, radioligand therapy with ¹⁷⁷Lu-PSMA-617 in metastasized castration-resistant early-onset prostate cancer patients refractory to chemotherapy yields similar response rates with a comparable safety profile, but is associated with shorter survival.

Update on radioligand therapy with 177Lu-PSMA for metastatic castration-resistant prostate cancer: clinical aspects and survival effects

OBJECTIVE

To give an updated overview on clinical aspects and survival effects of lutetium-177-prostate-specific membrane antigen (PSMA) (¹⁷⁷Lu-PSMA) radioligand therapy (RLT), a novel treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

PubMed/MEDLINE database was searched for relevant articles published up to March 2021. The search was restricted to English-language articles.

RESULTS

Current evidence from the literature consistently demonstrated the efficacy, safety, and survival benefit of ¹⁷⁷Lu-PSMA RLT in mCRPC. However, current data rely predominantly on retrospective analyses, showing heterogeneity of patient population and treatment protocols. More recently, results from the first randomized phase II study (TheraP) demonstrated that ¹⁷⁷Lu-PMSA therapy significantly improved prostate-specific antigen response rate (66% vs 37%) and had fewer grade 3/4 adverse events when compared to cabazitaxel in patients with docetaxel-pretreated, progressive mCRPC. This review is intended to provide an updated overview of treatment protocols and responses, toxicity profile, and survival effects of ¹⁷⁷Lu-PSMA RLT.

CONCLUSIONS

¹⁷⁷Lu-PSMA RLT has emerged as a promising targeted treatment in mCRPC. It is currently applied in compassionate use programs and following exhaustion of approved therapies. Crucial for establishing this treatment in routine clinical management will be the results of the phase III VISION trial, which may confirm the encouraging patient outcomes reported to date.

Lutetium-177 Labelled PSMA Targeted Therapy in Advanced Prostate Cancer: Current Status and Future Perspectives

Patients suffering from metastatic castration-resistant prostate cancer (mCRPC) have a poor prognosis. As a further treatment option ¹⁷⁷Lutetium (Lu) prostate-specific membrane antigen (PSMA) radioligand therapy gained a significant interest of many investigators. Several publications showed great response and prolonged survival with limited adverse events. However, to this point, it still remains unclear which patients benefit the most from ¹⁷⁷Lu-PSMA therapy, and how to improve the treatment regimen to achieve best outcome while minimizing potential adverse events. The efficacy for mCRPC patients is a given fact, and with the newly published results of the VISION trial its approval is only a matter of time. Recently, investigators started to focus on treating prostate cancer patients in earlier disease stages and in combination with other compounds. This review gives a brief overview of the current state and the future perspectives of ¹⁷⁷Lu labelled PSMA radioligand therapy.

Evolving Castration Resistance and Prostate Specific Membrane Antigen Expression: Implications for Patient Management

Metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease, despite multiple novel treatment options. The role of prostate-specific membrane antigen (PSMA) in the process of mCRPC development has long been underestimated. During the last years, a new understanding of the underlying molecular mechanisms of rising PSMA expression and its association with disease progression has emerged. Accurate understanding of these complex interactions is indispensable for a precise diagnostic process and ultimately successful treatment of advanced prostate cancer. The combination of different novel therapeutics such as androgen deprivation agents, 177LU-PSMA radioligand therapy and PARP inhibitors promises a new kind of efficacy. In this review, we summarize the current knowledge about the most relevant molecular mechanisms around PSMA in mCRPC development and how they can be implemented in mCRPC management.

Drug Repurposing of Pantoprazole and Vitamin C Targeting Tumor Microenvironment Conditions Improves Anticancer Effect in Metastatic Castration-Resistant Prostate Cancer

The effective and economical therapeutic strategy for metastatic castration-resistant prostate cancer (mCRPC) is still requested from patients, who are not available for Lu-177 or Ra-223 treatment. Drug repurposing as a cost-effective and time-saving alternative to traditional drug development has been increasingly discussed. Proton pump inhibitors (PPIs) such as pantroprazole, which are commonly used as antacids, have also been shown to be effective in cancer chemoprevention via induction of apoptosis in multiple cancer cell lines. Vitamin C is an essential micronutrient for human body, has been proposed as a potential anti-cancer agent. In this context, have we investigated the combination of vitamin C and pantoprazole for the management of metastatic castration-resistant prostate cancer (mCRPC). Six chosen human adenocarcinoma cell lines were used to investigate the influence of pantoprazole on the microenvironment of cancer cells (extracellular pH and production of exosomes). Tumor growth and tumor 18F-FDG uptake in PC3 xenografts were analyzed following varied treatment. Our in vitro Results have suggested that pantoprazole enhanced the cytotoxic activity of vitamin C by regulating pH values and production of exosomes in cancer cells. Moreover, the synergistic effect of pantoprazole and vitamin C was pH-dependent since pantoprazole was more effective at a slightly acidic pH. In vivo, the combined treatment using pantoprazole and vitamin C produced better therapeutic outcomes than treatment with vitamin C or pantoprazole alone, as demonstrated via tumor growth and uptake of 18F-FDG. Therefore, we suggest that pantoprazole combined with vitamin C could be as a possible strategy to manage mCRPC.

Biomarkers in Prostate-Specific Membrane Antigen Theranostics

Theranostics of prostate cancer (PC) represents a growing area of development of imaging agents and targeted radionuclide therapeutics against a major target, prostate specific membrane antigen (PSMA). In view of the encouraging efficacy from the use of ¹⁷⁷Lu and other radionuclides in metastatic castration-resistant prostate cancer (mCRPC), it is becoming increasingly important to identify surrogate markers that can help predict which patients are more likely to respond and experience improved survival. This review discusses potential predictors of efficacy of PSMA-targeted radionuclide therapies (TRT) segregated in three major categories: imaging, clinical and molecular.

PSMA Expression Predicts Early Biochemical Response in Patients with Metastatic Castration-Resistant Prostate Cancer under 177Lu-PSMA-617 Radioligand Therapy

Simple Summary

Prostate-specific membrane antigen (PSMA) is a promising target for both imaging and radioligand therapies (RLT) for men with prostate cancer. However, not all patients respond to RLT and some even progress early in the treatment course. We aimed to identify parameters to forecast which patients will achieve therapy response prior to commencing RLT. Therefore, we tested whether the tumor volume, the level of PSMA expression or a combination of both in metastases derived from PSMA-targeted molecular imaging prior to RLT can inform the treating physician whether a patient will respond to RLT. Compared to tumor volume, the level of PSMA-expression can better identify patients responding to RLT early in the treatment course.

Abstract

¹⁷⁷Lu-Prostate-specific membrane antigen (PSMA)-radioligand therapy (RLT) is a promising treatment option in patients with metastatic castration-resistant prostate cancer (mCRPC). We aimed to determine the predictive value of pretherapeutic PSMA-ligand positron emission tomography (PET) and established clinical parameters for early biochemical response after two cycles of RLT. In total, 71 mCRPC patients who had undergone PET/computed tomography (CT) with ⁶⁸Ga-PSMA-11 prior to two cycles of ¹⁷⁷Lu-PSMA-617 RLT were included. Malignant lesions on pretherapeutic PET/CTs were manually segmented and average maximum PSMA expression (maximum standardized uptake values, SUV_max), whole-body PSMA-tumor volume (TV), and whole-body total lesion (TL)-PSMA were calculated. We then tested the predictive performance of these parameters for early biochemical response (defined as prostate-sepcific antigen (PSA) decrease of ≥50% according to PCWG2) after two cycles of RLT, relative to established clinical parameters. Early PSA response was observed in 34/71 patients. PSA change after two cycles of RLT correlated with pretherapeutic SUV_max (r = −0.49; p < 0.001), but not with PSMA-TV (r = 0.02; p = 0.89) or TL-PSMA (r = −0.15; p = 0.22). A cut-off of 19.8 for SUV_max and 75.5 years for age was defined by receiver operating characteristics and revealed a significant outcome difference for early biochemical response between patients with adversely low vs. high PSMA expression and low vs. high age (p < 0.001). Multivariate analysis identified SUV_max (HR, 7.94, p = 0.001) and age (HR, 8.05, p = 0.002) as independent predictors for PSA response early in the treatment course. Thus, high age and high PSMA expression in patients scheduled for RLT identify patients with early biochemical response. This study provides a rationale for further prospective studies exploring PET-guided treatment intensification in selected patients.

177Lu-PSMA Therapy in Metastatic Castration-Resistant Prostate Cancer

The aim of this narrative review is to evaluate the current status of ¹⁷⁷Lu-PSMA (prostate specific membrane antigen) therapy for metastatic castration-resistant prostate cancer (mCRPC) in the light of the current literature. We also addressed patient preparation, therapy administration and side effect profiles. ¹⁷⁷Lu-PSMA therapy efficacy was assessed by using prospective trials, meta-analyses and major retrospective trials. Predictors of efficacy were also mentioned. Although there are some different approaches regarding the use of ¹⁷⁷Lu-PSMA therapy in different countries, this type of therapy is generally safe, with a low toxicity profile. From the oncological point of view, a PSA (prostate specific antigen) decline of ≥50% was seen in 10.6-69% of patients with mCRPC; whereas progression-free survival (PFS) was reported to be 3-13.7 months in different studies. Consequently, ¹⁷⁷Lu-PSMA therapy is a promising treatment in patients with mCRPC, with good clinical efficacy, even in heavily pretreated patients with multiple lines of systemic therapy. Currently, there are ongoing clinical trials in the United States, including a phase III multicenter FDA registration trial.

Imaging expression of prostate-specific membrane antigen and response to PSMA-targeted β-emitting radionuclide therapies in metastatic castration-resistant prostate cancer

BACKGROUND

Prostate-specific membrane antigen (PSMA)-targeted radionuclide therapy (TRT) has demonstrated efficacy and tolerability with a dose-response effect in phase I/II trials in men with metastatic castration-resistant prostate cancer (mCRPC). The need for positive PSMA imaging before PSMA-TRT to select patients is largely practiced, but its utility is not proven. Given target heterogeneity, developing a biomarker to identify the optimal patient population remains an unmet need. The aim of this study was to assess PSMA uptake by imaging and response to PSMA-TRT.

METHODS

We performed an analysis of men with mCRPC enrolled in sequential prospective phase I/II trials of PSMA-TRT. Each patient had baseline PSMA imaging by planar ¹¹¹ In and/or ¹⁷⁷ Lu SPECT (N = 171) or ⁶⁸ Ga-PSMA-11 PET/CT (N = 44), but the results were not used to include/exclude treatment. Semiquantitative imaging scores (IS) on a 0-4 scale were assigned based on PSMA uptake in tumors compared to liver uptake. We compared the ≥50% PSA decline response proportions between low (0-1) and high (2-4) PSMA IS using the χ² -test. We used multivariable logistic regression analysis to understand the relationship between independent and dependent variables, including IS, radionuclide activity (dose) administered, CALGB (Halabi) prognostic risk score, prior taxane use.

RESULTS

215 men with progressive mCRPC received PSMA-TRT as follows: ¹⁷⁷ Lu-J591 (n = 137), ¹⁷⁷ Lu-PSMA-617 (n = 44), ⁹⁰ Y-J591 (n = 28), ¹⁷⁷ Lu-J591 + ¹⁷⁷ Lu-PSMA-617 (n = 6). High PSMA expression (IS 2-4) was found in 160 (74.4%) patients and was significantly associated with more frequent ≥ 50% PSA reduction (26.2 vs. 7.3%, p = .006). On multivariate logistic regression analysis, higher IS was associated with a ≥50% decrease in PSA, even after accounting for CALGB (Halabi) prognostic score, the dose administered, and previous taxane use (OR, 4.72; 95% CI, 1.71-16.85; p = .006). Patients with low PSMA expression (N = 55, 24.7%) were less likely to respond. Thirteen of 26 (50%) with no PSMA uptake (IS = 0) had post-PSMA-TRT PSA decline with 2 (7.7%) having ≥ 50% PSA declines.

CONCLUSION

Collectively, the data provide evidence in favor of the hypothesis that patients with high PSMA uptake and high administered radionuclide dose correlate with a higher chance of response.

Optimizing PSMA Radioligand Therapy for Patients with Metastatic Castration-Resistant Prostate Cancer. A Systematic Review and Meta-Analysis

The aim of the review was to evaluate patient and treatment characteristics for patients with metastatic castration-resistant prostate cancer (mCRPC) treated with PSMA radioligand therapy (PRLT) associated with above-average outcome. The systematic review and meta-analysis followed recommendations by the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA). We searched for publications in PubMed, Embase, and ClinicalTrials.gov up to 31 September 2020. Thirty-six publications and four duplicates reported 2346 patients. Nearly two-thirds of the patients had bone metastases. Median overall survival (OS) was 16 months. Asymptomatic patients and patients with only lymph node metastases lived longer than symptomatic patients and patients with more extensive metastases. Patients treated with an intensified schedule of ¹⁷⁷Lu PRLT lived longer than those treated with a conventional schedule. Half of the patients obtained a PSA decline ≥ 50% and these patients lived longer than those with less PSA decline. Approximately 10% of the patients developed hematologic toxicity with anemia grade 3 as the most severe adverse effect. Characteristics for patients, cancer, restaging, and PRLT predict above average overall survival following treatment with PRLT.

Prediction of response and survival after standardized treatment with 7400 MBq 177Lu-PSMA-617 every 4 weeks in patients with metastatic castration-resistant prostate cancer

BACKGROUND AND AIMS

[¹⁷⁷Lu]Lu-PSMA-617 radioligand therapy (PSMA-RLT) is a new therapy for patients with metastatic castration-resistant prostate cancer (mCRPC). However, identification of reliable prognostic factors is hampered by heterogeneous treatment regimens applied in previous studies. Hence, we sought clinical factors able to predict response and survival to PSMA-RLT in a homogenous group of patients, all receiving 7400 MBq every 4 weeks.

PATIENTS AND METHODS

Data of 61 patients (mean age 71.6 ± 6.9 years, median basal PSA 70.7 [range 1.0-4890 μg/L]), pretreated with abiraterone/enzalutamide (75.4%) and docetaxel/cabazitaxel (68.9%), received three cycles of PSMA-RLT (mean 7321 ± 592 MBq) at four weekly intervals and were analyzed retrospectively. General medical conditions and laboratory parameters of every patients were regularly assessed. Response to therapy was based on PSA levels 1 month after the 3rd cycle. Binary logistic regression test and Kaplan-Meier estimates were used to evaluate predictors and overall survival (OS).

RESULTS

Forty-nine (80.3%) patients demonstrated a therapy response in terms of any PSA decline, while 21 (19.7%) patients showed increase or no changes in their PSA levels. Baseline hemoglobin (Hb) significantly predicted PSA reductions of ≥ 50% 4 weeks after receiving the 3rd PSMA-RLT (P = 0.01, 95% CI: 1.09-2.09) with an AUC of 0.68 (95% CI: 0.54-0.81). The levels of basal Hb and basal PSA were able to predict survival of patients, both P < 0.05 (relative risk 1.51 and 0.79, 95% CI: 1.09-2.09 and 0.43-1.46), respectively. In comparison to patients with reduced basal Hb, patients with normal basal Hb levels lived significantly longer (median survival not reached vs. 89 weeks, P = 0.016). Also, patients with basal PSA levels ≤ 650 μg/L had a significantly longer survival than patients with basal PSA levels > 650 μg/L (median survival not reached vs. 97 weeks, P = 0.031). Neither pretreatments with abiraterone/enzalutamide or docetaxel/cabazitaxel nor distribution of metastasis affected survival and rate of response to PSMA-RLT.

CONCLUSION

Basal Hb level is an independent predictor for therapy response and survival in patients receiving PSMA-RLT every 4 weeks. Both baseline PSA ≤ 650 μg/L and normal Hb levels were associated with longer survival.

Analysis of PSMA expression and outcome in patients with advanced Prostate Cancer receiving 177Lu-PSMA-617 Radioligand Therapy

Rationale: PSMA-PET-CT enables measuring molecular expression of prostate-specific membrane antigen (PSMA) in vivo, which is the target molecule of ¹⁷⁷Lu-PSMA-617 (Lu-PSMA) therapy. However, the correlation of PSMA expression and overall survival (OS) in patients treated with Lu-PSMA therapy is currently unclear; especially with regard to coexistence of high and low PSMA expressing metastases. To this end, this retrospective single arm study elucidates the correlation of PSMA expression and overall survival in patients treated with Lu-PSMA therapy. Additionally, PET based criteria to define low PSMA expression were explored. Methods: Eighty-five patients referred to Lu-PSMA therapy were included in the analysis. Pretherapeutic ⁶⁸Ga-PSMA-PET-CT scans were available for all patients. SUV_max of the highest PSMA expressing metastasis (PSMA_max), SUV_max of the lowest PSMA expressing metastasis (PSMA_min), and average SUV_max of all metastases (PSMA_average) amongst other PET parameters were measured for each patient. A log-rank cutoff-finder was used to determine low (lowPSMA_average) and high (highPSMA_average) average PSMA expression as well as low (lowPSMA_min) and high (highPSMA_min) minimal PSMA expression. Results: PSMA_average was a significant prognosticator of overall survival in contrast to PSMA_max (HR: 0.959; p = 0.047 vs. HR: 0.992; p = 0.231). Optimal log rank cut-offs were: PSMA_average = 14.3; PSMA_min = 10.2. Patients with low average PSMA expression (lowPSMA_average) had significantly shorter survival compared to those with high average expression (highPSMA_average) (5.3 vs. 15.1 months; p < 0.001; HR: 3.738, 95%CI = 1.953-7.154; p < 0.001). Patients with low PSMA expressing metastases (lowPSMA_min) had shorter survival compared to those without a low PSMA expressing metastasis (highPSMA_min) (p = 0.003; 7.9 months vs. 21.3; HR: 4.303, 95%CI = 1.521-12.178; p = 0.006). Patients that were classified as highPSMA_average but with lowPSMA_min had an intermediate overall survival (11.4 months; longer compared to lowPSMA_average, 5.3 months, p = 0.002; but shorter compared to highPSMA_min, 21.3 months, p = 0.02). Conclusion: Low average PSMA expression is a negative prognosticator of overall survival. Absence of low PSMA expressing metastases is associated with best overall survival and the maximum PSMA expression seems not suited to prognosticate overall survival. Low PSMA expression might therefore be a negative prognosticator for the outcome of patients treated with Lu-PSMA therapy. Future studies are warranted to elucidate the degree of low PSMA expression tolerable for Lu-PSMA therapy.

Neuroendocrine Differentiation and Response to PSMA-Targeted Radioligand Therapy in Advanced Metastatic Castration-Resistant Prostate Cancer: A Single-Center Retrospective Study

Neuroendocrine differentiation is associated with treatment failure and poor outcome in metastatic castration-resistant prostate cancer. We investigated the effect of circulating neuroendocrine biomarkers on the efficacy of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT). Methods: Neuroendocrine biomarker profiles (progastrin-releasing peptide, neuron-specific enolase, and chromogranin-A) were analyzed in 50 patients commencing ¹⁷⁷Lu-PSMA-617 RLT. The primary endpoint was a prostate-specific antigen response in relation to baseline neuroendocrine marker profiles. An additional endpoint was progression-free survival. Tumor uptake on posttherapeutic scans, a known predictive marker for response, was used as a control variable. Results: Neuroendocrine biomarker profiles were abnormal in most patients. Neuroendocrine biomarker levels did not predict treatment failure or early progression (P ≥ 0.13). By contrast, intense PSMA-ligand uptake in metastases predicted both treatment response (P = 0.0030) and reduced risk of early progression (P = 0.0111). Conclusion: Neuroendocrine marker profiles do not predict an adverse outcome from RLT. By contrast, high ligand uptake was confirmed to be crucial for achieving a tumor response.