Dosimetric Analysis of a Phase I Study of PSMA-Targeting Radiopharmaceutical Therapy With [177Lu]Ludotadipep in Patients With Metastatic Castration-Resistant Prostate Cancer.

OBJECTIVE: 177Lutetium [Lu] Ludotadipep is a novel prostate-specific membrane antigen targeting therapeutic agent with an albumin motif added to increase uptake in the tumors. We assessed the biodistribution and dosimetry of [177Lu]Ludotadipep in patients with metastatic castration-resistant prostate cancer (mCRPC). MATERIALS AND METHODS: Data from 25 patients (median age, 73 years; range, 60-90) with mCRPC from a phase I study with activity escalation design of single administration of [177Lu]Ludotadipep (1.85, 2.78, 3.70, 4.63, and 5.55 GBq) were assessed. Activity in the salivary glands, lungs, liver, kidneys, and spleen was estimated from whole-body scan and abdominal SPECT/CT images acquired at 2, 24, 48, 72, and 168 h after administration of [177Lu]Ludotadipep. Red marrow activity was calculated from blood samples obtained at 3, 10, 30, 60, and 180 min, and at 24, 48, and 72 h after administration. Organ- and tumor-based absorbed dose calculations were performed using IDAC-Dose 2.1. RESULTS: Absorbed dose coefficient (mean ± standard deviation) of normal organs was 1.17 ± 0.81 Gy/GBq for salivary glands, 0.05 ± 0.02 Gy/GBq for lungs, 0.14 ± 0.06 Gy/GBq for liver, 0.77 ± 0.28 Gy/GBq for kidneys, 0.12 ± 0.06 Gy/GBq for spleen, and 0.07 ± 0.02 Gy/GBq for red marrow. The absorbed dose coefficient of the tumors was 10.43 ± 7.77 Gy/GBq. CONCLUSION: [177Lu]Ludotadipep is expected to be safe at the dose of 3.7 GBq times 6 cycles planned for a phase II clinical trial with kidneys and bone marrow being the critical organs, and shows a high tumor absorbed dose.

Adherence to hormone therapy in patients with mCRPC: psychometric validation of the A-HT questionnaire.

Abstract: The incidence rate of prostate cancer (PCa) in many Western countries is high, contributing greatly to the cancer disease bur-den. In most cases, patients progress to metastatic disease defined as castration-resistant prostate cancer after androgen deprivation (mCRPC) following primary treatment where the majority of patients receive first-line new-generation oral hormonal therapies (HT) such as Abiraterone Acetate (AA) and Enzalutamide (ENZ). Despite the importance of correct intake of these drugs, adherence in patients with mCRPC is still poorly investigated and managed with measures not specific to this population. A self-report questionnaire was developed and validated with women with breast cancer treated with oral HT (A-BET). Therefore, this study aims to test the psychometric properties of this instrument on patients with mCRPC treated with AA or ENZ. A prospective observational validation study. The questionnaire was completed by all participants and again after 7/10 days by a randomized subsample to assess stability. Sixty-six patients completed the study (mean age of 72.8 years) and 31 completed the re-test (mean age of 72.7 years). Content validity reported excellent results. Cronbach's alpha of each item showed a strong correlation. Validation of an instrument to measure adherence to HT in patients with mCRPC can be a valuable tool for health professionals involved in patient care. In addition, having a population-specific validated instrument allows to make comparisons between results from different observations.

Prognostic role of early prostate specific antigen changes after [177 Lu]Lu-PSMA radioligand therapy of metastasized prostate cancer: A meta-analysis.

BACKGROUND: Approximately 10%-20% of prostate cancers progress to metastatic and castration-resistant forms (mCRPC). Radioligand (RLT) therapy with [177 Lu]Lu-prostate-specific membrane antigen (PSMA) is an emerging treatment for metastasized mCRPC and its efficacy is assessed not only but also by prostate specific antigen (PSA) measurement after 12 weeks or more after treatment. Our aim was to evaluate the role of early PSA measurement after RLT in predicting overall survival (OS) of mCRPC patients. METHODS: A systematic search on PubMed, Web Of Science and Scopus was performed from January to December 2022. PRISMA guidelines for prognostic studies was adopted. Risk of bias was assessed using quality of prognostic studies (QUIPS). RESULTS: Twelve studies at low-intermediate risk of bias, were included in the meta-analysis (1646 patients, mean age 70 years). About 50% of patients showed a PSA decline after 1-2 of [177 Lu]Lu-PSMA, and more than 30% reported a PSA decline ≥50%. The median OS range for patients with any PSA decline was 13-20 months, while for patients with stable or increased PSA, the median OS fell to 6-12 months. The OS rate for a PSA decline after the one-two [177 Lu]Lu-PSMA cycles was 0.39 (95% CI: 0.31-0.50), while OS for a PSA decline ≥50% was 0.69 (95% CI: 0.57-0.83). CONCLUSIONS: A PSA decline is observed in almost 50% of mCRPC patients after 1-2 [177 Lu]Lu-PSMA cycles, with a significantly longer OS compared to stable or increased PSA levels, respectively. Accordingly, any PSA decline after 1-2 cycles of therapy should be regarded as a favourable prognostic factor for OS.

177Lu-Prostate-specific Membrane Antigen Radioligand Therapy in Patients with Metastatic Castration-resistant Prostate Cancer.

A 76-year-old man with metastatic castration-resistant prostate carcinoma progressing with antiandrogen and taxane therapy was treated with lutetium 177 prostate-specific membrane antigen (PSMA)-617 and showed marked biochemical and imaging response, with improvement in clinical status and osseous pain. A summary of nuclear medicine theranostics with emphasis on PSMA targeting agents is presented.

Enzalutamide and Quality of Life in Biochemically Recurrent Prostate Cancer.

BACKGROUND: EMBARK, a controlled trial reported elsewhere, showed enzalutamide plus leuprolide (combination) and enzalutamide monotherapy prolonged metastasis-free survival versus placebo plus leuprolide (alone) in patients with high-risk biochemically recurrent prostate cancer. Health-related quality of life was also analyzed but not reported. METHODS: In EMBARK, patients with biochemical recurrence (prostate-specific antigen doubling time of ≤9 months) were randomly assigned (1:1:1) to combination (n=355), leuprolide-alone (n=358), or enzalutamide monotherapy (n=355). In this article we provide the patient-reported outcomes (PROs) from EMBARK at baseline and every 12 weeks until metastasis or death. The key end point was time to first and confirmed clinically meaningful deterioration (TTFD/TTCD) in pain and health-related quality of life using four PRO measures and predefined thresholds. RESULTS: At baseline, all groups had high health-related quality of life. For worst pain, the median TTFD was 19.35 months with leuprolide alone, 13.93 months with combination (hazard ratio, 1.08; 95% confidence interval [CI], 0.89 to 1.30) and 16.59 months with monotherapy (hazard ratio, 1.09; 95% CI, 0.90 to 1.31). The median TTCD was 66.27 months with leuprolide alone, 80.00 months with combination (hazard ratio, 0.82; 95% CI, 0.65 to 1.04), and 60.91 months with monotherapy (hazard ratio, 1.02; 95% CI, 0.82 to 1.28). For Functional Assessment of Cancer Therapy­Prostate total score, the median TTFD was 11.10 months with leuprolide alone, 8.31 months with combination (hazard ratio, 1.14; 95% CI, 0.95 to 1.36), and 8.38 months with monotherapy (hazard ratio, 1.17; 95% CI, 0.98 to 1.39). The median TTCD was 36.53 months with leuprolide alone, 38.77 months with combination (hazard ratio, 1.04; 95% CI, 0.85 to 1.28), and 30.55 months with monotherapy (hazard ratio, 1.16; 95% CI, 0.95 to 1.41). CONCLUSIONS: The PROs from EMBARK show that both enzalutamide combination and monotherapy versus leuprolide alone, with oncologic benefits noted above, preserved high health-related quality of life in patients with high-risk biochemical recurrence of prostate cancer. (Funded by Pfizer and Astellas Pharma; ClinicalTrials.gov number, NCT02319837.)

HOW TO OPTIMALLY SEQUENCE AVAILABLE THERAPY LINES IN ADVANCED PROSTATE CANCER.

Optimal sequencing of available therapy lines in patients with advanced prostate cancer often poses quite a challenge. The guidelines are sometimes equivocal and clinical trial data are not always applicable to a particular patient. There is a difference in availability of therapy options throughout the world. In decision making, a patient as a whole should be taken into consideration, not just the stage and biology of the disease, but also patient's age, performance status, comorbidities, previous therapy lines, drug's safety profile and patient's preferences. This review article will show certain therapeutic options in the treatment of advanced hormone-sensitive prostate cancer and castration resistant prostate cancer: non- metastatic and metastatic. An attempt will be made to clarify the optimal sequencing.

Loss of EHF facilitates the development of treatment-induced neuroendocrine prostate cancer.

The rising of a highly aggressive subtype of castration-resistant prostate cancer (CRPC) named treatment-induced neuroendocrine prostate cancer (t-NEPC) after androgen deprivation therapy (ADT) is well known for its features of the neuroendocrine differentiation (NED) and androgen receptor (AR) independence. However, t-NEPC is still largely unknown. Here, we found that EHF is notably depressed in t-NEPC tumors, patient-derived xenografts, transgenic mice, and cell models. Results from cell lines uncovered that ADT represses EHF expression, which is required for the ADT-induced NED. Mechanism dissection revealed that ADT decreases the EHF transcription via relieving the AR binding to different androgen-responsive elements, which then promotes the expression and enzymatic activity of enhancer of zeste homolog 2 (EZH2), consequently catalyzing tri-methylation lysine 27 of histone H3 for transcriptional repression of its downstream genes to promote the NED. Furthermore, preclinical studies from cell and mice models proved that recovery of EHF expression or using EZH2 inhibitor can attenuate aggressive properties of CRPC cells, hinder the progression of t-NEPC, and promote the response of CPRC cells to enzalutamide. Together, we elucidate that the ADT/AR/EHF/EZH2 signaling is required for the ADT-enhanced NED and plays a critical role in the progression of t-NEPC.

Sox2 is necessary for androgen ablation-induced neuroendocrine differentiation from Pten null Sca-1+ prostate luminal cells.

Prostate adenocarcinoma undergoes neuroendocrine differentiation to acquire resistance toward antihormonal therapies. The underlying mechanisms have been investigated extensively, among which Sox2 has been shown to play a critical role. However, genetic evidence in mouse models for prostate cancer to support the crucial role of Sox2 is missing. The adult mouse prostate luminal cells contain both castration-resistant Sox2-expressing Sca-1+ cells and castration-responsive Sca-1- cells. We show that both types of the luminal cell are susceptible to oncogenic transformation induced by loss of function of the tumor suppressor Pten. The tumors derived from the Sca-1+ cells are castration resistant and are more inclined to develop castration-induced neuroendocrine differentiation. Genetic ablation of Sox2 suppresses neuroendocrine differentiation but does not impact the castration-resistant property. This study provides direct genetic evidence that Sox2 is necessary for androgen ablation-induced neuroendocrine differentiation of Pten null prostate adenocarcinoma, corroborates that the lineage status of the prostate cancer cells is a determinant for its propensity to exhibit lineage plasticity, and supports that the intrinsic features of cell-of-origin for prostate cancers can dictate their clinical behaviors.

Senescence and castration resistance in prostate cancer: A review of experimental evidence and clinical implications.

The development of Castration-Resistant Prostate Cancer (CRPC) remains a major challenge in the treatment of this disease. While Androgen Deprivation Therapy (ADT) can result in tumor shrinkage, a primary response of Prostate Cancer (PCa) cells to ADT is a senescent growth arrest. As a response to cancer therapies, senescence has often been considered as a beneficial outcome due to its association with stable growth abrogation, as well as the potential for immune system activation via the Senescence-Associated Secretory Phenotype (SASP). However, there is increasing evidence that not only can senescent cells regain proliferative capacity, but that senescence contributes to deleterious effects of cancer chemotherapy, including disease recurrence. Notably, the preponderance of work investigating the consequences of therapy-induced senescence on tumor progression has been performed in non-PCa models. Here, we summarize the evidence that ADT promotes a senescent response in PCa and postulate mechanisms by which senescence may contribute to the development of castration-resistance. Primarily, we suggest that ADT-induced senescence may support CRPC development via escape from senescence, by cell autonomous-reprogramming, and by the formation of a pro-tumorigenic SASP. However, due to the scarcity of direct evidence from PCa models, the consequences of ADT-induced senescence outlined here remain speculative until the relationship between senescence and CRPC can be experimentally defined.

Transcriptional regulation of the Nkx3.1 gene in prostate luminal stem cell specification and cancer initiation via its 3' genomic region.

NK3 homeobox 1 (Nkx3.1), a transcription factor expressed in the prostate epithelium, is crucial for maintaining prostate cell fate and suppressing tumor initiation. Nkx3.1 is ubiquitously expressed in luminal cells of hormonally intact prostate but, upon androgen deprivation, exclusively labels a type of luminal stem cells named castration-resistant Nkx3.1-expressing cells (CARNs). During prostate cancer initiation, Nkx3.1 expression is frequently lost in both humans and mouse models. Therefore, investigating how Nkx3.1 expression is regulated in vivo is important for understanding the mechanisms of prostate stem cell specification and cancer initiation. Here, using a transgenic mouse line with destabilized GFP, we identified an 11-kb genomic region 3' of the Nkx3.1 transcription start site to be responsible for alterations in Nkx3.1 expression patterns under various physiological conditions. We found that androgen cell-autonomously activates Nkx3.1 expression through androgen receptor (AR) binding to the 11-kb region in both normal luminal cells and CARNs and discovered new androgen response elements in the Nkx3.1 3' UTR. In contrast, we found that, in Pten-/- prostate tumors, loss of Nkx3.1 expression is mediated at the transcriptional level through the 11-kb region despite functional AR in the nucleus. Importantly, the GFP reporter specifically labeled CARNs in the regressed prostate only in the presence of cell-autonomous AR, supporting a facultative model for CARN specification.