A Retrospective Analysis of the Safety and Activity of Lutetium-177-Prostate-Specific Membrane Antigen Radionuclide Treatment in Older Patients with Metastatic Castration-Resistant Prostate Cancer

Investigating Combination Therapy: The Role of Lutetium-177 PSMA-617 Radioligand Therapy and Androgen Receptor Pathway Inhibitors in Metastatic Castration-Resistant Prostate Cancer

Background: The combination of Lutetium-177 (Lu-177) PSMA-617 radioligand therapy (RLT) with androgen receptor pathway inhibitors (ARPIs) has shown promise in metastatic castration-resistant prostate cancer (mCRPC). However, real-world data on the efficacy and safety of this combination are limited. This study aimed to evaluate the impact of combination therapy with Lu-177 PSMA-617 RLT and ARPIs on progression-free survival (PFS) and overall survival (OS) in patients with mCRPC. Methods: In this retrospective study, 104 mCRPC patients receiving Lu-177 PSMA-617 RLT at our institution between December 2017 and January 2024 were divided into the following two groups those receiving Lu-177 PSMA-617 RLT plus ARPI (n = 34) and those receiving Lu-177 PSMA-617 RLT alone (n = 70). Patients received 150 to 200 millicuries Lu-177 PSMA-617 RLT in each cycle. PFS and zOS were assessed using Kaplan-Meier analysis and Cox proportional hazard models. Results: The combination therapy significantly prolonged median PFS compared to Lu-177 PSMA-617 RLT alone (11 vs. 5.6 months; HR, 0.47; 95% CI, 0.28-0.79; p < 0.01). A trend towards improved OS was also observed in the combination group (20.3 vs. 15.9 months; HR, 0.58; 95% CI, 0.33-1.02; p = 0.06). Age was a significant predictor of OS (21.2 vs. 12.4 months for younger vs. older patients; p < 0.01), while Gleason score and visceral involvement did not significantly impact PFS. The safety profile indicated that adverse effects were generally comparable between the two groups, with no statistically significant differences in the incidence of anemia, neutropenia, thrombocytopenia, nephrotoxicity, or hepatotoxicity. Conclusions: This study provides evidence that combining Lu-177 PSMA-617 RLT with ARPIs may significantly improve PFS in mCRPC patients. The potential OS benefit warrants further investigation in larger prospective trials. Age should be considered when making treatment decisions for mCRPC patients.

PSMA-based therapeutics for prostate cancer

INTRODUCTION

The prostate cancer (PCa) consists the most frequently diagnosed malignancy of urogenital system in males. Traditionally, treatment of localized PCa was based on surgery or radiotherapy while hormonotherapy was used in more advanced stages. However, the implementation of radiolabels has revolutionized the landscape of prostate cancer. Specifically, prostate-specific membrane antigen (PSMA) has been investigated in different aspects of PCa therapeutic era.

AREAS COVERED

A literature review is presented about the implications of PSMA radiolabels on prostate cancer treatment. PSMA tracers were initially used as an imaging technique. Afterwards, PSMA labeled with isotopes presenting cytotoxic abilities, such as lutetium-117 and actinium-225, while reports exist about the use of radioligand immunotherapy. Meanwhile, ongoing trials examine the development of novel radionuclides as well as the evolution of the PSMA-targeted ligands.

EXPERT OPINION

Currently, PSMA radioligand treatment of prostate cancer is approved in the metastatic stage of the disease. Meanwhile, a variety of trials exist about its possible role in less advanced stages. However, plenty of parameters should be addressed before these implementations, such as PSMA dosage, dosimetry issues, and its safety profile. A future well-designed study with proper patient selection is mandatory to further explore PSMA radioligand theranostics perspectives.

Outcomes in studies regarding older patients with prostate cancer: A systematic review

INTRODUCTION

Older patients are often deemed ineligible for clinical research, and many frequently-used endpoints and outcome measures are not as relevant for older patients for younger ones. This systematic review aimed to present an overview of outcomes used in clinical research regarding patients over the age of 65 years with prostate cancer.

MATERIALS AND METHODS

PubMed and Embase were systematically searched to identify studies on prostate cancer (treatment) in patients aged ≥65 between 2016 and 2023. Data on title, study design, number of participants and age, stage of disease, treatment, and investigated outcomes were synthesized and descriptively analyzed.

RESULTS

Sixty-eight studies were included. Of these most included patients over 65 years, while others used a higher age. Overall, 39 articles (57.3%) reported on survival-related outcomes, 22 (32.4%) reported on progression of disease and 38 (55.9%) used toxicity or adverse events as an outcome measure. Health-related quality of life and functional outcomes were investigated in 29.4%, and cognition in two studies. The most frequently investigated survival-related outcomes were overall and cancer-specific survival (51.3%); however, 38.5% only studied overall survival.

DISCUSSION

The main focus of studies included in this review remains survival and disease progression. There is limited attention for health-related quality of life and functional status, although older patients often prioritize the latter. Future research should incorporate outcome measures tailored to the aged population to improve care for older patients with prostate cancer.

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.

177Lu-PSMA Therapy for Metastatic Castration-Resistant Prostate Cancer: A Mini-Review of State-of-the-Art

BACKGROUND

Prostate specific membrane antigen (PSMA) ligand labeled with Lutetium-177 (177Lu) is a promising therapeutic option for metastatic castration-resistant prostate cancer (mCRPC). Several prospective and retrospective studies as well as clinical trials are completed or underway. This has ultimately led to the approval of this therapy by the US Food and Drug Administration (FDA) on March 23 2022. Our work aims to present a mini-review of the most recent research performed and the potential future directions of 177Lu-PSMA-radioligand therapy (RLT) for mCRPC patients.

MAIN BODY

For patients with mCRPCwho have met the eligibility criteria for 177Lu-PSMA RLT, numerous studies and trials are either ongoing or have been completed. The studies included in this review have reported overall biochemical response, defined as a prostate-specific antigen (PSA) decline of at least 50%, in at least 44% of patients with mCRPC. The median ranges of overall survival (OS) and radiographic progression-free survival (rPFS) were reported within 10.7-56 and 3.6-16 months, respectively. With data from several retrospective and prospective studies published, the safety of 177Lu-PSMA RLT in mCRPC has been confirmed and demonstrated by its low toxicity profile. Various studies have published pharmacokinetic/pharmacodynamic models to better understand the absorption, distribution, metabolism, and excretion of the RLT in this patient population. Findings have been published for 177Lu-PSMA RLT alone and in combination with other agents. We summarize their findings in our review.

CONCLUSIONS

The efficacy of 177Lu-PSMA RLT for patients with mCRPC has been proven thus far with promising results: PSA response, OS and rPFS when used alone or in combination with other treatment options, relative to the standard treatment options alone. The low toxicity profile noted also proves the safety of 177Lu-PSMA RLT in these patients.

Pharmacological Optimization of PSMA-Based Radioligand Therapy

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

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.

How aging of the global population is changing oncology

Population aging is causing a demographic redistribution with implications for the future of healthcare. How will this affect oncology? First, there will be an overall rise in cancer affecting older adults, even though age-specific cancer incidences continue to fall due to better prevention. Second, there will be a wider spectrum of health functionality in this expanding cohort of older adults, with differences between “physiologically older” and “physiologically younger” patients becoming more important for optimal treatment selection. Third, greater teamwork with supportive care, geriatric, mental health and rehabilitation experts will come to enrich oncologic decision-making by making it less formulaic than it is at present. Success in this transition to a more nuanced professional mindset will depend in part on the development of user-friendly computational tools that can integrate a complex mix of quantitative and qualitative inputs from evidence-based medicine, functional and cognitive assessments, and the personal priorities of older adults.

Safety and Efficacy of 177Lutetium-PSMA-617 Radioligand Therapy Shortly after Failing 223Radium-Dichloride

Bone-seeking 223Radium-dichloride (223Ra) is an established treatment prolonging survival and reducing morbidity in selected patients with metastatic castration-resistant prostate cancer (mCRPC) with skeletal involvement. Radioligand therapy with 177Lutetium-PSMA-617 (177Lu-PSMA-617) has been increasingly implemented in patients with mCRPC failing conventional treatment options. In this study, the safety and efficacy of 177Lu-PSMA-617 in patients with progressive bone involvement under treatment with 223Ra was assessed. Twenty-eight men (median age 73 years, range 63–89 years) with progressive mCRPC, who started 177Lu-PSMA-617 within 8 weeks after the last 223Ra administration, received a median of 4 (IQR 3–6) and a total of 120 cycles of 223Ra and a median of 4 (IQR 2–7) cycles 177Lu-PSMA-617 with a mean treatment activity of 6.5 ± 1.2 GBq per cycle, reaching a mean cumulative activity of 30.7 ± 23.4 GBq. A PSA response (≥50% PSA decline 12 weeks after the first 177Lu-PSMA-617 cycle) was observed in 18/28 (64.3%) patients and imaging-based partial remission (PR) was observed in 11/28 (39.3%) patients. Median imaging-based progression-free survival (PFS) was 10 (95% CI, 6–14) months and median overall survival (OS) was 18 (95% CI, 14–22) months. Patients with low bone tumor burden (2–20 lesions) had a significantly longer OS (28 vs. 14 months, p < 0.045) compared to patients with a high tumor burden (>20 lesions). Grade ≥ 3 hematological toxicity was observed in six patients after their last treatment cycle with anemia, leukopenia and thrombocytopenia in 5/28 (17.9%), 4/28 (14.3%) and 6/28 (21.4%) patients, respectively. In progressive bone-metastatic mCRPC patients, prompt initiation of 177Lu-PSMA-617 after failing 223Ra is effective with an acceptable toxicity profile.

PSMA Theranostics: Science and Practice

Prostate cancer (PCa) causes significant morbidity and mortality in men globally. While localized PCa may be managed with curative intent by surgery and/or radiation therapy, the management of advanced hormone resistant metastatic disease (mCRPC) is more challenging. Theranostics is a principle based on the ability to use an organ specific ligand and label it to both a diagnostic and a therapeutic agent. The overexpression of prostate specific membrane antigen (PSMA) on prostate cancer cells creates a unique opportunity for development of targeted radionuclide therapy. The use of both beta and alpha emitting particles has shown great success. Several clinical trials have been initiated assessing the efficacy and safety profile of these radionuclide agents. The results are encouraging with PSMA directed radioligand therapy performing well in patients who have exhausted all other standard treatment options. Future studies need to assess the timing of introduction of these radionuclide therapies in the management schema of mCRPC. Drugs or therapies are not without side effects and targeted radionuclide therapies presents a new set of toxicities including xerostomia and myelosuppression. New therapeutic strategies are being explored to improve outcomes while keeping toxicities to a minimum. This review aims to look at the various PSMA labelled tracers that form part of the theragnostic approach and subsequently delve into the progress made in the area of radionuclide therapy.