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

Targeted radioligand therapy: physics and biology, internal dosimetry and other practical aspects during 177Lu/225Ac treatment in neuroendocrine tumors and metastatic prostate cancer

Radioligand therapy (RLT) has garnered significant attention due to the recent emergence of innovative and effective theranostic agents, which showed promising therapeutic and prognostic results in various cancers. Moreover, understanding the interaction between different types of radiation and biological tissues is essential for optimizing therapeutic interventions These concepts directly apply to clinical RLTs and play a crucial role in determining the efficacy and toxicity profile of different radiopharmaceutical agents. Personalized dosimetry is a powerful tool that aids in estimating patient-specific absorbed doses in both tumors and normal organs. Dosimetry in RLT is an area of active investigation, as our current understanding of the relationship between absorbed dose and tissue damage is primarily derived from external-beam radiation therapy. Further research is necessary to comprehensively comprehend this relationship in the context of RLTs. In the present review, we present a thorough examination of the involvement of 177Lu/225Ac radioisotopes in the induction of direct and indirect DNA damage, as well as their influence on the initiation of DNA repair mechanisms in cancer cells of neuroendocrine tumors and metastatic prostate cancer. Current data indicate that high-energy α-emitter radioisotopes can directly impact DNA structure by causing ionization, leading to the formation of ionized atoms or molecules. This ionization process predominantly leads to the formation of irreparable and intricate double-strand breaks (DSBs). On the other hand, the majority of DNA damage caused by β-emitter radioisotopes is indirect, as it involves the production of free radicals and subsequent chemical reactions. Beta particles themselves can also physically interact with the DNA molecule, resulting in single-strand breaks (SSBs) and potentially reversible DSBs.

Theranostics Nuclear Medicine in Prostate Cancer

Theranostic Nuclear Medicine is based on the idea of combining the same molecule (or drug) with different radioisotopes for both diagnosis and treatment, a concept that emerged in the early 1940s with the use of radioactive iodine for thyroid diseases. Theranostic Nuclear Medicine has since expanded to diseases of higher incidence, such as prostate cancer, with several imaging methods used to assess the extent of the disease and the corresponding radiopharmaceuticals used for treatment. For example, by detecting osteoblastic metastases by bone scintigraphy, corresponding radiopharmaceuticals with therapeutic properties can be administered to eliminate or reduce pain associated with metastases and/or determine overall survival gain. The purpose of this review is to discuss the role of Theranostic Nuclear Medicine in prostate cancer, addressing the main diagnostic imaging studies with their corresponding treatments in the Theranostic model.

Navigating the landscape of theranostics in nuclear medicine: current practice and future prospects

Theranostics refers to the combination of diagnostic biomarkers with therapeutic agents that share a specific target expressed by diseased cells and tissues. Nuclear medicine is an exciting component explored for its applicability in theranostic concepts in clinical and research investigations. Nuclear theranostics is based on the employment of radioactive compounds delivering ionizing radiation to diagnose and manage certain diseases employing binding with specifically expressed targets. In the realm of personalized medicine, nuclear theranostics stands as a beacon of potential, potentially revolutionizing disease management. Studies exploring the theranostic profile of radioactive compounds have been presented in this review along with a detailed explanation of radioactive compounds and their theranostic applicability in several diseases. It furnishes insights into their applicability across diverse diseases, elucidating the intricate interplay between these compounds and disease pathologies. Light is shed on the important milestones of nuclear theranostics beginning with radioiodine therapy in thyroid carcinomas, MIBG labelled with iodine in neuroblastoma, and several others. Our perspectives have been put forth regarding the most important theranostic agents along with emerging trends and prospects.

Homologous Recombination Repair Testing Patterns and Outcomes in mCRPC by Alteration Status and Race

Background

Alterations in DNA damage repair genes in advanced prostate cancer (PC) may impact responses to therapy and clinical outcomes. This study described homologous recombination repair (HRR) testing patterns and clinical outcomes among patients with metastatic castration-resistant prostate cancer (mCRPC) by HRR alteration status and race in the United States (US).

Methods

Clinical data in the nationwide (US-based) Flatiron Health-Foundation Medicine, Inc. (FMI) Metastatic PC Clinico-Genomic Database were evaluated (01/01/2011-12/31/2022). Patients initiating first-line (1L) mCRPC therapy on or after mCRPC diagnosis were included. Testing patterns, time-to-next treatment, overall survival (OS), and time-to-prostate specific antigen response were described.

Results

Of the 1367 patients with mCRPC and at least one HRR panel test prior to or on the date of 1L mCRPC therapy initiation, 332 (24.3%) were HRR positive (White patients: n = 219 [66.0%]; Black patients: n = 37 [11.1%]) and 1035 (75.7%) were HRR negative (White patients: n = 702 [67.8%]; Black patients: n = 84 [8.1%]). The mean time between first positive test and 1L mCRPC therapy initiation date was 588 days (White patients: 589 days; Black patients: 639 days). Among HRR positive relative to negative patients, trends for faster progression (respective 12-month rate overall: 71.1% and 63.7%; White patients: 72.5% and 64.0%; Black patients: 65.4% and 56.4%), shorter OS (respective 24-month rate overall: 46.8% and 51.9%; White patients: 48.6% and 46.2%; Black patients: 52.8% and 54.1%), and decreased treatment response (respective 12-month rate overall: 24.3% and 37.9%; White patients: 24.5% and 35.2%; Black patients: 17.0% and 43.9%) were observed.

Conclusion

Patients with mCRPC positive for HRR alterations tended to exhibit poorer treatment responses and clinical outcomes than those with a negative status. These findings highlight the importance of timely genetic testing in mCRPC, particularly among Black patients, and the need for improved 1L targeted therapies to address the unmet need in HRR positive mCRPC.

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.

Therapeutic efficacy and safety results of 177Lu-PSMA therapy in metastatic castration-resistant prostate cancer patients: first experience of a developing South Asian Country

OBJECTIVE

Metastatic castration resistant-prostate cancer (mCRPC) is deadly condition that remains incurable despite various therapies. Initial studies have shown promising results with Lutetium-177 prostate-specific membrane antigen ( 177 Lu-PSMA) therapy for advanced prostate cancer. However, most of the published efficacy and safety data is retrospective. The purpose of the study was to prospectively evaluate the therapeutic efficacy and safety results of 177 Lu-PSMA therapy in mCRPC patients after 2 cycles.

METHODS

Twenty-five patients of mCRPC, treated with standard care treatment were enrolled for 2 cycles of 177 Lu-PSMA therapy. Prostate-specific antigen (PSA), Eastern Cooperative Oncology Group (ECOG) performance status, Visual Analogue Score (VAS) and Analgesic Quantification Scale (AQS) for efficacy and hemoglobin, total leukocyte, platelets and serum creatinine for toxicity were recorded pre and post-therapy. Paired sample t-test was used for statistical analysis.

RESULTS

Treated patients with mean PSA level of 157 ng/ml received mean dose of 6.84 GBq of 177 Lu-PSMA. For PSA, partial response (PR) was seen in 11/25 (44%), stable disease (SD) in 8/25 (32%) and progressive disease (PD) in 6/25 (24%) patients. Grade 1 and 2 hemoglobin toxicity was seen in 5/25 (20%) and 6/25 (24%) patients respectively. No patient developed grade 3 or 4 bone marrow toxicities. Grade 1 and 2 nephrotoxicity was seen in 1 patient each. Statistically significant difference was seen in ECOG, VAS and AQS scores ( P  < 0.001). No significant nephrotoxicity was observed ( P  = 0.558).

CONCLUSION

Efficacy and safety of 177 Lu-PSMA therapy after 2 cycles have shown significant PSA response and pain palliation in heavily pretreated mCRPC patients.

Clinical Advances and Perspectives in Targeted Radionuclide Therapy

Targeted radionuclide therapy has become increasingly prominent as a nuclear medicine subspecialty. For many decades, treatment with radionuclides has been mainly restricted to the use of iodine-131 in thyroid disorders. Currently, radiopharmaceuticals, consisting of a radionuclide coupled to a vector that binds to a desired biological target with high specificity, are being developed. The objective is to be as selective as possible at the tumor level, while limiting the dose received at the healthy tissue level. In recent years, a better understanding of molecular mechanisms of cancer, as well as the appearance of innovative targeting agents (antibodies, peptides, and small molecules) and the availability of new radioisotopes, have enabled considerable advances in the field of vectorized internal radiotherapy with a better therapeutic efficacy, radiation safety and personalized treatments. For instance, targeting the tumor microenvironment, instead of the cancer cells, now appears particularly attractive. Several radiopharmaceuticals for therapeutic targeting have shown clinical value in several types of tumors and have been or will soon be approved and authorized for clinical use. Following their clinical and commercial success, research in that domain is particularly growing, with the clinical pipeline appearing as a promising target. This review aims to provide an overview of current research on targeting radionuclide therapy.

Case Report: Long-term complete response to PSMA-targeted radioligand therapy and abiraterone in a metastatic prostate cancer patient

Despite decades of research and clinical trials, metastatic castration-resistant prostate cancer (mCRPC) remains incurable and typically fatal. Current treatments may provide modest increases in progression-free survival but can come with significant adverse effects and are disaggregated from the diagnostic imaging needed to fully assess the spread of metastatic disease. A theranostic approach, using radiolabeled ligands that target the cell surface protein PSMA, simplifies the visualization and disease treatment process by enabling both to use similar agents. Here, we describe an exemplary case wherein a gentleman in his 70s with mCRPC on diagnosis was treated with 177Lu-PSMA-617 and abiraterone, and remains disease-free to date, over five years later.

Safety and Therapeutic Optimization of Lutetium-177 Based Radiopharmaceuticals

Peptide receptor radionuclide therapy (PRRT) using Lutetium-177 (¹⁷⁷Lu) based radiopharmaceuticals has emerged as a therapeutic area in the field of nuclear medicine and oncology, allowing for personalized medicine. Since the first market authorization in 2018 of [¹⁷⁷Lu]Lu-DOTATATE (Lutathera®) targeting somatostatin receptor type 2 in the treatment of gastroenteropancreatic neuroendocrine tumors, intensive research has led to transfer innovative ¹⁷⁷Lu containing pharmaceuticals to the clinic. Recently, a second market authorization in the field was obtained for [¹⁷⁷Lu]Lu-PSMA-617 (Pluvicto®) in the treatment of prostate cancer. The efficacy of ¹⁷⁷Lu radiopharmaceuticals are now quite well-reported and data on the safety and management of patients are needed. This review will focus on several clinically tested and reported tailored approaches to enhance the risk-benefit trade-off of radioligand therapy. The aim is to help clinicians and nuclear medicine staff set up safe and optimized procedures using the approved ¹⁷⁷Lu based radiopharmaceuticals.

Lutetium-177 Prostate Specific Membrane Antigen Therapy in a Patient With Double Malignancy and Single Functioning Kidney: A Case Report

Lutetium-177 labeled with 617 types of Prostate Specific Membrane Antigen (¹⁷⁷Lu PSMA-617) Radio-ligand Therapy (RLT) is an emerging modality of choice for the treatment of metastatic castration-resistant prostate carcinoma (mCRPC). After it is administered intravenously, it is excreted primarily through the kidneys. Physiological excretion and concomitant expression of PSMA receptors on renal tissues are associated with potential renal toxicity, a matter of concern while treating patients with multiple doses of RLT. There are published articles that have demonstrated the safe use of ¹⁷⁷Lu PSMA-617 in patients with bilateral fair-functioning kidneys; however, only a single study has been published that has evaluated its safety in patients with solitary-functioning kidneys. The uniqueness of this case report lies in the fact that we have documented the renal safety profile of ¹⁷⁷Lu PSMA-617 therapy after multiple doses in a patient who presented with double malignancy (metastatic castration-resistant prostate carcinoma and left renal cell carcinoma) and had a single-functioning right kidney.

Incorporating radioligand therapy in clinical practice in the United States for patients with prostate cancer

Prostate cancer (PC) is the second most commonly diagnosed cancer in the United States. Advanced PC evolves to metastatic castration-resistant PC (mCRPC). Theranostics combining prostate-specific membrane antigen-targeted positron emission tomography imaging and radioligand therapy (RLT) represents a precision medicine approach to PC treatment. With the recent approval of lutetium Lu 177 (¹⁷⁷Lu) vipivotide tetraxetan for men with mCRPC, the utilization of RLT will increase. In this review, we suggest a framework for incorporating RLT for PC into clinical practice. A search of PubMed and Google Scholar was performed using keywords related to PC, RLT, prostate-specific membrane antigen, and novel RLT centers. The authors also provided opinions based on their clinical experience. The setup and operation of an RLT center requires the diligence and cooperation of a well-trained multidisciplinary team committed to patient safety and clinical efficacy. Administrative systems should ensure that treatment scheduling, reimbursement, and patient monitoring are efficient. For optimal outcomes, the clinical care team must have an organizational plan that delineates the full range of required tasks. Establishing new RLT centers for treatment of PC is possible with appropriate multidisciplinary planning. We provide an overview of the key elements to consider when establishing a safe, efficient, and high-quality RLT center.

Genomic characterization of metastatic castration-resistant prostate cancer patients undergoing PSMA radioligand therapy: A single-center experience

BACKGROUND

Genomic defects in DNA-damage repair (DDR) mechanisms have been proposed to affect the radiosensitivity of prostate cancers. In this study, we intended to evaluate the prevalence of genetic alterations in a cohort of metastatic castration-resistant prostate cancer (mCRPC) patients undergoing radioligand therapy (RLT) with prostate-specific membrane antigen (PSMA)-inhibitors as well as the impact of such mutations on treatment outcomes.

METHODS

Data of consecutive mCRPC patients from 2017 to 2021 who were treated with PSMA-RLT and underwent next-generation sequencing (NGS) were collected and analyzed for response and survival outcomes.

RESULTS

In 95 patients of mCRPC treated with PSMA-RLT, 15 patients (median age: 66 years, range: 50-73 years; [¹⁷⁷ Lu]Lu-PSMA-617, n = 12; [²²⁵ Ac]Ac-PSMA-617, n = 3) underwent NGS. The median progression-free survival (PFS) of this cohort was 3 months (95% confidence interval: 1.6-4.4 months). On NGS, 21 genetic alterations were reported in 10/15 (67%) patients, of which 13 were DDR-associated alterations involving the genes: ATM (n = 3), BRCA2 (n = 3), TP53 (n = 2), PTEN (n = 2), FANCD2 (n = 1), FANCM (n = 1), and NBN (n = 1). Overall, 5/15 (33%) patients harbored six pathogenic variants (BRCA2, n = 2; ATM, n = 1; TP53, n = 1; PTEN, n = 2). No significant difference was noted for the biochemical response, radiological response, PFS, and overall survival between the patients with and without genetic alterations.

CONCLUSIONS

Patients of mCRPC undergoing PSMA-RLT were frequently seen to harbor DDR-associated aberrations, albeit with no significant impact on treatment outcomes. Large prospective trials comparing PSMA-RLT-related outcomes in DDR-deficient and -proficient patients are required to bring out the differences, if any, in a more observable manner.

PSMA-based 18F-DCFPyL PET: a better choice than multiparametric MRI for prostate cancer diagnosis?

Owing to the high tissue contrast, multiparametric MRI (mpMRI) has already been the most widely applied imaging method for prostate cancer. Recently, prostate-specific membrane antigen (PSMA) ligands for nuclear imaging are emerging as a promising modality in prostate cancer, especially since the 2 PET/CT agents (68Ga-PSMA-11 and 18F-DCFPy) approved by U.S. Food and Drug Administration (FDA). However, limited studies have performed the comparison of mpMRI versus recently approved 18F-DCFPyL PET/CT. In this issue of AJNMMI, Lu et al. compared the performance of 18F-DCFPyL PET/CT and pelvic mpMRI in intermediate-high risk and biochemical recurrent prostate cancer patients. The results demonstrated the two modalities have a good concordance rate for patient-based analysis, and 18F-DCFPyL PET/CT has a better diagnostic performance in detecting lymph node metastases and bone metastases for lesion-based analysis. The use of 18F-DCFPyL PET/CT provides more diagnostic confidence to better assess prostate cancer lesions.

Very-Low-Dose Radiation and Clinical Molecular Nuclear Medicine

Emerging molecular and precision medicine makes nuclear medicine a de facto choice of imaging, especially in the era of target-oriented medical care. Nuclear medicine is minimally invasive, four-dimensional (space and time or dynamic space), and functional imaging using radioactive biochemical tracers in evaluating human diseases on an anatomically configured image. Many radiopharmaceuticals are also used in therapies. However, there have been concerns over the emission of radiation from the radionuclides, resulting in wrongly neglecting the potential benefits against little or any risks at all of imaging to the patients. The sound concepts of radiation and radiation protection are critical for promoting the optimal use of radiopharmaceuticals to patients, and alleviating concerns from caregivers, nuclear medicine staff, medical colleagues, and the public alike.