177Lu-PSMA-I&T for Treatment of Metastatic Castration-Resistant Prostate Cancer: Prognostic Value of Scintigraphic and Clinical Biomarkers

Current clinical application of lutetium‑177 in solid tumors (Review)

Radionuclide-based therapy represents a novel treatment regimen for tumors. Among these therapies, lutetium-177 (177Lu) has gained significant attention due to its stability and safety, as well as its ability to emit both γ and β rays, allowing for both imaging with single photon emission computed tomography and tumor treatment. As a result, 177Lu can be used for both diagnosis and treatment for diseases such as prostatic and gastric cancer. Therefore, based on the available data, the present review provides a brief overview of the clinical applications of 177Lu-targeted radionuclide therapy in metastatic prostate cancer, neuroendocrine tumors and other types of solid tumors, and highlights the current therapeutic effect, reduction in damage to normal tissues and future research directions, including the development of new nuclides and the application of more nuclides in different tumors. In the future, such treatments could be used in more tumors.

Influence of Molecular Design on the Tumor Targeting and Biodistribution of PSMA-Binding Tracers Labeled with Technetium-99m

Previously, we designed the EuK-based PSMA ligand BQ0413 with an maE3 chelator for labeling with technetium-99m. It showed efficient tumor targeting, but our preclinical data and preliminary clinical results indicated that the renal excretion levels need to be decreased. We hypothesized that this could be achieved by a decrease in the ligand's total negative charge, achieved by substituting negatively charged glutamate residues in the chelator with glycine. The purpose of this study was to evaluate the tumor targeting and biodistribution of two new PSMA inhibitors, BQ0411 and BQ0412, compared to BQ0413. Conjugates were radiolabeled with Tc-99m and characterized in vitro, using PC3-pip cells, and in vivo, using NMRI and PC3-pip tumor-bearing mice. [99mTc]Tc-BQ0411 and [99mTc]Tc-BQ0412 demonstrated PSMA-specific binding to PC3-pip cells with picomolar affinity. The biodistribution pattern for the new conjugates was characterized by rapid excretion. The tumor uptake for [99mTc]Tc-BQ0411 was 1.6-fold higher compared to [99mTc]Tc-BQ0412 and [99mTc]Tc-BQ0413. [99mTc]Tc-BQ0413 has demonstrated predominantly renal excretion, while the new conjugates underwent both renal and hepatobiliary excretion. In this study, we have demonstrated that in such small targeting ligands as PSMA-binding EuK-based pseudopeptides, the structural blocks that do not participate in binding could have a crucial role in tumor targeting and biodistribution. The presence of a glycine-based coupling linker in BQ0411 and BQ0413 seems to optimize biodistribution. In conclusion, the substitution of amino acids in the chelating sequence is a promising method to alter the biodistribution of [99mTc]Tc-labeled small-molecule PSMA inhibitors. Further improvement of the biodistribution properties of BQ0413 is needed.

Advancements in PSMA ligand radiolabeling for diagnosis and treatment of prostate cancer: a systematic review

Prostate cancer(PCa), a leading global health concern, profoundly impacts millions of men worldwide. Progressing through two stages, it initially develops within the prostate and subsequently extends to vital organs such as lymph nodes, bones, lungs, and the liver. In the early phases, castration therapy is often employed to mitigate androgen effects. However, when prostate cancer becomes resistant to this treatment, alternative strategies become imperative. As diagnostic and treatment methodologies for prostate cancer continually advance, radioligand therapy (RLT) has emerged as a promising avenue, yielding noteworthy outcomes. The fundamental principle of RLT involves delivering radionuclide drugs to cancerous lesions through specific carriers or technologies. Subsequently, these radionuclide drugs release radioactive energy, facilitating the destruction of cancer cell tissues. At present, the positron emission tomography (PET) targeting PSMA has been widely developed for the use of diagnosis and staging of PCa. Notably, FDA-approved prostate-specific membrane antigen (PSMA) targeting agents, such as 68Ga-PSMA-11 and 177Lu-PSMA-617, represent significant milestones in enhancing diagnostic precision and therapeutic efficacy. This review emphasizes the current research status and outcomes of various radionuclide-labeled PSMA ligands. The objective is to provide valuable insights for the continued advancement of diagnostic and therapeutic approaches in the realm of prostate cancer.

Prostate-Specific Membrane Antigen-Ligand Therapy: What the Radiologist Needs to Know

The discovery and clinical development of radiolabeled small-molecule ligands targeting prostate-specific membrane antigen (PSMA) has had a profound influence on the field of nuclear medicine. Such agents have been successfully deployed for both imaging and therapeutic applications. In particular, PSMA radioligand therapy (PRLT) has been shown to be a life-prolonging therapy for men with metastatic, castration-resistant prostate cancer and has also brought nuclear medicine physicians and nuclear radiologists into the forefront of direct patient care. In this review, we will discuss the clinical study data regarding the efficacy and toxicities related to PRLT, outline the key personnel that any center offering PRLT should have, offer salient clinical examples, and provide an overview of future directions for PRLT. As PRLT continues to evolve as a treatment modality, it is paramount that nuclear medicine physicians and nuclear radiologists understand the clinical context, management implications, and practical aspects so as to best deliver high-value care to patients.

Improved Quality of Life in Metastatic Castration-Resistant Prostate Cancer Patients Receiving Consecutive Cycles of 177Lu-PSMA I&T

The aim of this retrospective analysis was to evaluate health-related quality of life (HRQoL) for patients with metastatic castration-resistant prostate cancer (mCRPC) receiving consecutive cycles of 177Lu-prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) using the reliable and validated European Organisation for Research and Treatment of Cancer core quality-of-life (QoL) questionnaire. In addition, differences in HRQoL between patients with early discontinuation of treatment because of disease progression and patients who were defined as eligible for treatment continuation were analyzed. Methods: In total, 60 mCRPC patients were included in this analysis. The European Organisation for Research and Treatment of Cancer core QoL questionnaire was completed at baseline, before each treatment cycle up to the sixth treatment cycle, and at the time of PSMA-ligand PET/CT scans after the second and fourth treatment cycles. QoL assessment included global health status, functional scales, and symptom burden during treatment. Results: Global health was significantly improved at the second and fourth cycles of 177Lu-PSMA RLT (P = 0.014 and P = 0.039, respectively). In line with this, role and emotional functioning showed significant improvements at the second and fourth treatment cycles (role functioning, P = 0.045 and P = 0.048, respectively, and emotional functioning, P = 0.035 and P = 0.007, respectively). In addition, compared with baseline, fatigue and pain were significantly alleviated at the second and fourth treatment cycles (pain, P = 0.035 and P = 0.034, respectively, and fatigue, P = 0.042 and P = 0.041, respectively). Other aspects of HRQoL, even if not significantly improved, remained stable over time, except for deterioration of fatigue at the study's end (P = 0.014) and reduction of dyspnea at the second treatment cycle (P = 0.012). Patients with early discontinuation of treatment showed a concordant decline in HRQoL. Conclusion: mCRPC patients showed significant improvement in HRQoL in the course of treatment with 177Lu-PSMA RLT. Furthermore, patients with early discontinuation of treatment showed an analogous decline in HRQoL.

Lu-177-Labeled Hetero-Bivalent Agents Targeting PSMA and Bone Metastases for Radionuclide Therapy

Prostate-specific membrane antigen (PSMA) is an excellent target for imaging and radionuclide therapy of prostate cancer. Recently, [177Lu]Lu-PSMA-617 (Pluvicto) was approved by the FDA for radionuclide therapy. To develop hetero-bivalent agents targeting both PSMA and bone metastasis, [177Lu]Lu-P17-079 ([177Lu]Lu-1) and [177Lu]Lu-P17-081 ([177Lu]Lu-2) were prepared. In vivo biodistribution studies of [177Lu]Lu-PSMA-617, [177Lu]Lu-1, and [177Lu]Lu-2 in mice bearing PC3-PIP (PSMA positive) tumor showed high uptake in PSMA-positive tumor (14.5, 14.7, and 11.3% ID/g at 1 h, respectively) and distinctively different bone uptakes (0.52, 6.52, and 5.82% ID/g at 1 h, respectively). PET imaging using [68Ga]Ga-P17-079 ([68Ga]Ga-1) in the same mouse model displayed excellent images confirming the expected dual-targeting to PSMA-positive tumor and bone. Results suggest that [177Lu]Lu-P17-079 ([177Lu]Lu-1) is a promising candidate for further development as a hetero-bivalent radionuclide therapy agent targeting both PSMA expression and bone metastases for the treatment of prostate cancer.

The Impact of PSMA PET-Based Eligibility Criteria Used in the Prospective Phase II TheraP Trial in Metastatic Castration-Resistant Prostate Cancer Patients Undergoing Prostate-Specific Membrane Antigen-Targeted Radioligand Therapy

Prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) has shown encouraging results for treatment of metastatic castration-resistant prostate cancer (mCRPC) in the prospective, multicenter, randomized phase II TheraP study. The inclusion criteria for that study comprised a pretherapeutic ⁶⁸Ga-PSMA-11 PET scan showing sufficient tumor uptake using a predefined threshold and the absence of ¹⁸F-FDG-positive, PSMA ligand-negative tumor lesions. However, the prognostic value of these PET-based inclusion criteria remains unclear. Therefore, we evaluated the outcome of mCRPC patients treated with PSMA RLT using TheraP as well as other TheraP-based PET inclusion criteria. Methods: First, patients were dichotomized into 2 groups whose PSMA PET scans did (TheraP contrast-enhanced PSMA [cePSMA] PET-positive) or did not (TheraP cePSMA PET-negative) fulfill the inclusion criteria of TheraP. Notably, unlike in TheraP, ¹⁸F-FDG PET was not performed on our patients. Prostate-specific antigen (PSA) response (PSA decline ≥ 50% from baseline), PSA progression-free survival, and overall survival (OS) were compared. Additionally, patients were further dichotomized according to predefined SUV_max thresholds different from those used in TheraP to analyze their potential impact on outcome as well. Results: In total, 107 mCRPC patients were included in this analysis (TheraP cePSMA PET-positive, n = 77; TheraP cePSMA PET-negative, n = 30). PSA response rates were higher in TheraP cePSMA PET-positive patients than in TheraP cePSMA PET-negative patients (54.5% vs. 20%, respectively; P = 0.0012). The median PSA progression-free survival (P = 0.007) and OS (P = 0.0007) of patients were significantly longer in the TheraP cePSMA PET-positive group than in the TheraP cePSMA PET-negative group. Moreover, being in the TheraP cePSMA PET-positive group was identified as a significant prognosticator of longer OS (P = 0.003). The application of different SUV_max thresholds for a single hottest lesion demonstrated no influence on outcome in patients eligible for PSMA RLT. Conclusion: Patient selection for PSMA RLT according to the inclusion criteria of TheraP led to a better treatment response and outcome in our preselected patient cohort. However, a relevant number of patients not fulfilling these criteria also showed substantial rates of response.

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.

[177Lu]Lu-PSMA-Radioligand Therapy Efficacy Outcomes in Taxane-Naïve Versus Taxane-Treated Patients with Metastatic Castration-Resistant Prostate Cancer: A Systematic Review and Metaanalysis

Radioligand therapy (RLT) with ¹⁷⁷Lu-prostate-specific membrane antigen (PSMA) inhibitors ([¹⁷⁷Lu]Lu-PSMA) is currently approved for patients with metastatic castration-resistant prostate cancer (mCRPC) after progression with at least 1 taxane and 1 androgen-receptor-pathway inhibitor. However, the impact of prior chemotherapy on [¹⁷⁷Lu]Lu-PSMA-RLT outcomes is debatable, with various studies showing inconsistent results. This study was conducted to precisely evaluate the impact of prior taxane chemotherapy on response and survival outcomes in mCRPC patients after [¹⁷⁷Lu]Lu-PSMA-RLT. Methods: This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Searches in PubMed, Scopus, and Embase were made using relevant key words, and articles up to December 2022 were included. The endpoints included prostate-specific antigen (PSA) response rate (RR), progression-free survival, and overall survival (OS). Individual patient data were pooled when feasible. Univariate odds ratios (ORs) and hazard ratios (HRs) were extracted from the individual articles, and pooled estimates and 95% CIs were generated using metaanalysis. Results: Thirteen articles comprising 2,068 patients were included. In 6 articles (553 patients), taxane-naïve patients had significantly better odds of biochemical response after [¹⁷⁷Lu]Lu-PSMA-RLT (pooled OR, 1.82; 95% CI, 1.21-2.71). Individual patient data metaanalysis for PSA RRs in 3 articles revealed a significantly higher PSA RR in the taxane-naïve versus taxane-treated patients (57.1% vs. 39.5%; difference, 17.6%; 95% CI, 5.6%-28.9%). Further, taxane-naïve status was also a predictor of significantly better progression-free survival (5 articles; 1,027 patients; pooled HR, 0.60; 95% CI, 0.51-0.69) and OS (8 articles; 1,594 patients; pooled HR, 0.54; 95% CI, 0.43-0.68) after [¹⁷⁷Lu]Lu-PSMA-RLT. There was no evidence of publication bias. Conclusion: mCRPC patients with no prior taxanes had significantly better outcomes after [¹⁷⁷Lu]Lu-PSMA-RLT than did taxane-treated patients. Further trials evaluating [¹⁷⁷Lu]Lu-PSMA-RLT in the taxane-naïve setting are now required.

Evaluation of Lactate Dehydrogenase and Alkaline Phosphatase as Predictive Biomarkers in the Prognosis of Hepatocellular Carcinoma and Development of a New Nomogram

Background

Tumor proliferation is frequently accompanied by aberrant enzyme production. We aim to investigate the potential predictive value of both plasma alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in patients with HCC and to develop a nomogram to assess the prognosis of HCC.

Methods

The trial involved 2327 patients between May 2015 and March 2022. Within 7 days of enrollment, the levels of ALP and LDH were measured, and their association with survival was assessed. And we had developed and validated a new nomogram based on ALD and ALP.

Results

Using X-tile software, the optimal cut-off values were determined to be ALP = 172 U/L and LDH = 241 U/L. The high ALP (≥ 172), LDH (≥ 241), and ALP/LDH (≥ 0.91) groups had lower median overall survival (mOS) than low ALP (< 172), LDH (< 241), and ALP/LDH (< 0.91) groups (all p < 0.001). In addition, elevated ALP and LDH levels are independent negative prognostic indicators. Moreover, we established that the area under the curve (AUC) values of the predicted 1-, 2-, and 3-year survival rates of receiver operating characteristic curve (ROC) based on the nomogram were 0.79, 0.77, and 0.74, respectively. In addition, the calibration curves and decision curve analyses (DCA) demonstrated that this model possessed strong predictive capability.

Conclusion

ALP, LDH and ALP/LDH can be employed as biomarkers for predicting the prognosis of HCC. Furthermore, the nomograph based on ALH and ALP demonstrates good HCC prediction performance. For HCC patients with high ALH or ALP or ALP/LDH, close surveillance program and adjuvant therapy should be considered.