¹77Lu-PSMA radioligand therapy for metastatic castration-resistant prostate cancer. / Behandling av kastrasjonsresistent metastatisk prostatakreft med [¹77Lu]PSMA-radioligand.

Background: Treatment of castration-resistant metastatic prostate cancer with [¹77Lu]PSMA radioligand. Case presentation: A man in his seventies with metastatic prostate cancer received castration therapy for four years, developing castration-resistant disease. PET/CT with [68Ga]PSMA-11 showed high uptake in metastatic lymph nodes. The patient received 7.4 GBq [¹77Lu]PSMA-I&T (Curium, Finland) as five treatments at five-week intervals. Five weeks after the first treatment, p-PSA dropped from 154 to 53 µg/L. Five weeks after the fifth treatment, p-PSA was 1.8 µg/L. [68Ga]PSMA-11 PET/CT showed significant reduction in the size of metastases, with the largest decreasing in diameter from 10 to 4 mm. Seven months after the fifth treatment, p-PSA increased to 14.3 µg/L, and [68Ga]PSMA-11 PET/ CT revealed additional skeletal metastases, while the lymph node metastases remained unchanged. Thus, the treatment had a good but temporary effect on the metastases. Interpretation: Treatment with [¹77Lu]PSMA radioligand resulted in a temporary regression of the metastases.

Quantitative 68Ga-PSMA-11 PET and Clinical Outcomes in Metastatic Castration-resistant Prostate Cancer Following 177Lu-PSMA-617 (VISION Trial).

Background Lutetium 177 [177Lu]Lu-PSMA-617 (177Lu-PSMA-617) is a prostate-specific membrane antigen (PSMA)-targeted radioligand therapy for metastatic castration-resistant prostate cancer (mCRPC). Quantitative PSMA PET/CT analysis could provide information on 177Lu-PSMA-617 treatment benefits. Purpose To explore the association between quantitative baseline gallium 68 [68Ga]Ga-PSMA-11 (68Ga-PSMA-11) PET/CT parameters and treatment response and outcomes in the VISION trial. Materials and Methods This was an exploratory secondary analysis of the VISION trial. Eligible participants were randomized (June 2018 to October 2019) in a 2:1 ratio to 177Lu-PSMA-617 therapy (7.4 GBq every 6 weeks for up to six cycles) plus standard of care (SOC) or to SOC only. Baseline 68Ga-PSMA-11 PET parameters, including the mean and maximum standardized uptake value (SUVmean and SUVmax), PSMA-positive tumor volume, and tumor load, were extracted from five anatomic regions and the whole body. Associations of quantitative PET parameters with radiographic progression-free survival (rPFS), overall survival (OS), objective response rate, and prostate-specific antigen response were investigated using univariable and multivariable analyses (with treatment as the only other covariate). Outcomes were assessed in subgroups based on SUVmean quartiles. Results Quantitative PET parameters were well balanced between study arms for the 826 participants included. The median whole-body tumor SUVmean was 7.6 (IQR, 5.8-9.9). Whole-body tumor SUVmean was the best predictor of 177Lu-PSMA-617 efficacy, with a hazard ratio (HR) range of 0.86-1.43 for all outcomes (all P < .001). A 1-unit whole-body tumor SUVmean increase was associated with a 12% and 10% decrease in risk of an rPFS event and death, respectively. 177Lu-PSMA-617 plus SOC prolonged rPFS and OS in all SUVmean quartiles versus SOC only, with no identifiable optimum among participants receiving 177Lu-PSMA-617. Higher baseline PSMA-positive tumor volume and tumor load were associated with worse rPFS (HR range, 1.44-1.53 [P < .05] and 1.02-1.03 [P < .001], respectively) and OS (HR range, 1.36-2.12 [P < .006] and 1.04 [P < .001], respectively). Conclusion Baseline 68Ga-PSMA-11 PET/CT whole-body tumor SUVmean was the best predictor of 177Lu-PSMA-617 efficacy in participants in the VISION trial. Improvements in rPFS and OS with 177Lu-PSMA-617 plus SOC were greater among participants with higher whole-body tumor SUVmean, with evidence for benefit at all SUVmean levels. ClinicalTrials.gov identifier: NCT03511664 Published under a CC BY 4.0 license. Supplemental material is available for this article.

Therapeutic response and safety of radioligand therapy with 177Lu-PSMA-617 in metastatic castration-resistant prostate cancer patients.

Prostate cancer is one of the most common cancers and leading cause of death due to cancer across the globe. This persuaded researchers to devise innovative treatment modalities that may prove effective, safe, and demonstrate better outcomes in terms of patient morbidity and survival. The advancement in theranostics such as lutetium-177 (177Lu)-PSMA-617 radioligand therapies can target prostate cancer cells causing negligible or no damage to most of the normal tissues in patients. It has been proven to effectively improve the quality of life and progression-free survival. In this study, stage IV metastatic castration-resistant prostate cancer patients were treated with 177Lu-PSMA-617, and the therapeutic response and safety of 177Lu-PSMA-617 radioligand therapy were evaluated six months after the treatment. Additionally, molecular docking studies were also conducted to find the possible mechanism at the molecular level that causes the effectiveness of 177Lu-PSMA-617 in prostate cancer.

Clinical Trial Protocol for VIOLET: A Single-Center, Phase I/II Trial Evaluation of Radioligand Treatment in Patients with Metastatic Castration-Resistant Prostate Cancer with [161Tb]Tb-PSMA-I&T.

[177Lu]Lu-PSMA is an effective class of therapy for patients with metastatic castration-resistant prostate cancer (mCRPC); however, progression is inevitable. The limited durability of response may be partially explained by the presence of micrometastatic deposits, which are energy-sheltered and receive low absorbed radiation with 177Lu due to the approximately 0.7-mm mean pathlength. 161Tb has abundant emission of Auger and conversion electrons that deposit a higher concentration of radiation over a shorter path, particularly to single tumor cells and micrometastases. 161Tb has shown in vitro and in vivo efficacy superior to that of 177Lu. We aim to demonstrate that [161Tb]Tb-PSMA-I&T will deliver effective radiation to sites of metastatic prostate cancer with an acceptable safety profile. Methods: This single-center, single-arm, phase I/II trial will recruit 30 patients with mCRPC. Key eligibility criteria include a diagnosis of mCRPC with progression after at least one line of taxane chemotherapy (unless medically unsuitable) and androgen receptor pathway inhibitor; prostate-specific membrane antigen-positive disease on [68Ga]Ga-PSMA-11 or [18F]DCFPyL PET/CT (SUVmax ≥ 20); no sites of discordance on [18F]FDG PET/CT; adequate bone marrow, hepatic, and renal function; an Eastern Cooperative Oncology Group performance status of no more than 2, and no prior treatment with another radioisotope. The dose escalation is a 3 + 3 design to establish the safety of 3 prespecified activities of [161Tb]Tb-PSMA-I&T (4.4, 5.5, and 7.4 GBq). The maximum tolerated dose will be defined as the highest activity level at which a dose-limiting toxicity occurs in fewer than 2 of 6 participants. The dose expansion will include 24 participants at the maximum tolerated dose. Up to 6 cycles of [161Tb]Tb-PSMA-I&T will be administered intravenously every 6 wk, with each subsequent activity reduced by 0.4 GBq. The coprimary objectives are to establish the maximum tolerated dose and safety profile (Common Terminology Criteria for Adverse Events version 5.0) of [161Tb]Tb-PSMA-I&T. Secondary objectives include measuring absorbed radiation dose (Gy), evaluating antitumor activity (prostate-specific antigen 50% response rate, radiographic and prostate-specific antigen progression-free survival, overall survival, objective response rate), and evaluating pain (Brief Pain Inventory-Short Form) and health-related quality of life (Functional Assessment of Cancer Therapy-Prostate and Functional Assessment of Cancer Therapy-Radionuclide Therapy). Conclusion: Enrollment was completed in February 2024. Patients are still receiving [161Tb]Tb-PSMA-I&T.

Stereotactic Body Radiotherapy for Oligoprogression in Castration-Resistant Prostate Cancer: Early Toxicity Analysis of the TRAP Trial.

AIMS: To assess toxicity and patient quality of life after stereotactic body radiotherapy (SBRT) to oligoprogressive disease (OPD) in patients with metastatic castrate-resistant prostate cancer (CRPC) on androgen receptor targeted agents (ARTA). MATERIAL AND METHODS: This phase II trial enrolled patients with metastatic CRPC with ≤ 2 oligoprogressive lesions in bone, lymph node, lung, or prostate. All patients were receiving systemic treatment with abiraterone or enzalutamide at the time of oligoprogression. All patients received SBRT to the OPD site(s) and continued the current ARTA. Patients received 30 Gy in 5 fractions (alternate days) to the OPD site. The primary endpoint of the trial is to assess if SBRT to OPD sites results in progression free survival of >6 months. The primary endpoint for this toxicity analysis is the rate of grade 3 or higher adverse events at any timepoint up to 6 months after SBRT. Secondary endpoints included comparing pre- and post-SBRT patient-related outcomes reported using visual analogue scale scores and EQ-5D health questionnaire. RESULTS: Forty enrolled patients had at least 6 months of follow-up at the time of analysis. Grade 3 or higher toxicity from any cause recorded using common terminology criteria for adverse events and radiation therapy oncology group was found in 8/40 (20%) of patients, but only 1/40 (2.5%) was deemed possibly related to SBRT. There was no significant difference in mean EQ5D visual analogue scale score from baseline to each timepoint after SBRT (p = 0.449). CONCLUSION: In this prospective phase II clinical trial for OPD whilst on ARTA in the CRPC setting, we report low grade ≥ 3 toxicity after SBRT. There is no discernible change in patient-reported quality of life due to SBRT treatment. The final results of progression-free survival and toxicity of SBRT treatment will be reported once further follow-up is complete.

Real-world safety and effectiveness of radium-223 in patients with metastatic castration-resistant prostate cancer: Interim analyses of the prospective, observational RAPIT study.

Several life-prolonging therapies for metastatic castration-resistant prostate cancer (mCRPC) are available, including radium-223 dichloride (223Ra), which was approved based on phase 3 data demonstrating improved overall survival (OS) and a favorable safety profile. To date, real-world evidence for 223Ra use in Taiwan is from three studies of <50 patients. This observational study (NCT04232761) enrolled male patients with histologically/cytologically confirmed mCRPC with bone metastases from centers across Taiwan. 223Ra was prescribed as part of routine practice by investigators. Patients with prior 223Ra treatment were excluded. The primary objective was to assess 223Ra safety; secondary objectives evaluated efficacy parameters, including OS. Overall, 224 patients were enrolled. Most patients had an Eastern Cooperative Oncology Group performance status of 0/1 (79.0%) and ≤20 bone metastases (69.2%); no patients had visceral metastases. 223Ra was first- or second-line therapy in 23.2% and 47.7% of patients, respectively. The total proportion of patients who received 5-6 223Ra cycles was 68.8%; this proportion was greater with first-line use (84.3%) than second- (65.7%) or third-/fourth-line use (64.1%). More chemotherapy-naïve patients (61.9%) completed the 6-cycle 223Ra treatment than chemotherapy-exposed patients (56.7%). Any-grade treatment-emergent adverse events (TEAEs) and serious TEAEs occurred in 54.0% and 28.6% of patients, respectively, while 12% experienced 223Ra-related adverse events. Median OS was 15.7 months (95% confidence interval 12.13-19.51); patients receiving 5-6 223Ra injections and earlier 223Ra use had longer OS than those receiving fewer injections and later 223Ra use. 223Ra provides a well-tolerated and effective treatment for Taiwanese patients with mCRPC and bone metastases.

Next-level precision medicine: why the theragnostic approach is the future.

Theragnostics represents one of the most innovative fields of precision medicine with a huge potential in the field of oncology in the next years. The use of a pair of selective radiopharmaceuticals for cellular receptors, used for diagnostic and therapeutic purposes (PRRT), finds applications in the Neuroendocrine tumors and metastatic Castration-Resistant prostate cancer (mCRPC) thanks, respectively, to somatostatin receptor agonists and PSMA-based peptides. Further evolutions of theragnostics will be possible to the radioimmunoconjugates used both in the diagnostic (Immuno-PET) and in the therapeutic fields (radioimmunotherapy). It is evident that in the "omics-era," theragnostics could become a necessary method, not only in order to improve our knowledge of tumor biology, but also, to find more and more targeted therapies in a multidisciplinary context and in a tailor-based approach.

Multidisciplinary real-world management of metastatic castration-sensitive prostate cancer: A French national study (PROFILE study).

While androgen deprivation therapy (ADT) has been the standard of care for patients with metastatic castration-sensitive prostate cancer (mCSPC), recent strategies like intensification of systemic treatment (Rozet et al., 2020) (i.e. adding another treatment to ADT) and radiotherapy have improved overall survival. PROFILE, a national retrospective multicentric real-world study, involved patients with mCSPC recruited by medical oncologists, urologists, and radiation oncologists, and who started treatment between November 2020 and May 2021. Patients by sites were included consecutively. Data were collected from medical records. Primary objectives were to: (1) describe retrospectively the characteristics of whole population of patients with mCSPC as well as subgroups defined by prognostic factors in France at diagnosis; (2) identify current practices for managing mCSPC in a real-life clinical setting. Among the 416 patients with mCSPC included in the PROFILE study, 315 (76%) were synchronous (metastasis at the initial diagnosis) and 101 (24%) were metachronous patients (metastasis diagnosed post-progression). A majority (83% of synchronous and 73% of metachronous patients) received an intensified systemic treatment (ADT plus ARSI [androgen-receptor signaling inhibitors]±chemotherapy±primary tumour radiotherapy±metastasis-directed therapy [MDT]), while only 40% of low-volume patients received prostate radiotherapy. This study depicts the standardization of new therapeutic strategies for patients with mCSPC in France with most of them receiving an intensified treatment, mainly with ADT+ARSI (64% of synchronous intensified patients and 76% of metachronous intensified patients). Most of patients were assessed using conventional imaging (CT scan and/or bone scan). Overall, PROFILE results are in line with French and European guidelines for diagnosis, management, and follow-up of such patients (Rozet et al., 2020; Cornford et al., 2021).

225 Ac-PSMA-617 Augmentation in High-Risk mCRPC Undergoing 177 Lu-PSMA-617 Radioligand Therapy : Pilot Experience From a Prospective Registry.

PURPOSE: This pilot study investigates the efficacy and safety profile as well as predictive biomarkers of 225 Ac-PSMA-617-augmented 177 Lu-PSMA-617 radioligand therapy (RLT) in a cohort of high-risk patients with metastatic castration-resistant prostate cancer (mCRPC), enrolled in a prospective registry (NCT04833517). PATIENTS AND METHODS: A group of n = 33 high-risk mCRPC patients received 177 Lu-PSMA-617 RLT, augmented by 1 or more cycles of 225 Ac-PSMA-617. Response was assessed by prostate-specific antigen (PSA) serum value after 2 cycles of treatment. Overall survival (OS) and PSA-based progression-free survival were evaluated using Kaplan-Meier analysis. To assess the side effect profile, Common Terminology Criteria for Adverse Events were applied. In total, 12 potential pretherapeutic biomarkers were tested for association with OS. RESULTS: The median decrease in serum PSA value was -49.1%, and 16/33 (48.5%) patients experienced a partial response after 2 cycles RLT. The median PSA-based progression-free survival and median OS was 7.2 and 14.8 months, respectively. Alkaline phosphatase ( P < 0.001), lactate dehydrogenase ( P = 0.035), Eastern European Oncology Group Performance Score ( P = 0.037), and the presence of visceral metastases ( P = 0.029) revealed significant association with OS in Kaplan-Meier analysis (log-rank test). Most of the recorded adverse events were rated as mild or moderate. Higher-grade adverse events were very limited with only 1 case (3.0%) of grade 3 anemia. Treatment-related mild xerostomia was recorded in 6/33 (18.2%) patients. CONCLUSIONS: 225 Ac-PSMA-617 augmentation in high-risk mCRPC undergoing 177 Lu-PSMA-617 RLT appears to be an effective treatment option with a favorable safety profile. The pretherapeutic values of alkaline phosphatase, lactate dehydrogenase, the Eastern European Oncology Group Performance Score, and the presence of visceral metastases may be appropriate biomarkers predicting survival outcome of this treatment regimen.

Hematological and renal toxicity in mice after three cycles of high activity [177Lu]Lu-PSMA-617 with or without human α1-microglobulin.

Radioligand therapy with [177Lu]Lu-PSMA-617 can be used to prolong life and reduce tumor burden in terminally ill castration resistant prostate cancer patients. Still, accumulation in healthy tissue limits the activity that can be administered. Therefore, fractionated therapy is used to lower toxicity. However, there might be a need to reduce toxicity even further with e.g. radioprotectors. The aim of this study was to (i). establish a preclinical mouse model with fractionated high activity therapy of three consecutive doses of 200 MBq [177Lu]Lu-PSMA-617 in which we aimed to (ii). achieve measurable hematotoxicity and nephrotoxicity and to (iii). analyze the potential protective effect of co-injecting recombinant α1-microglobulin (rA1M), a human antioxidant previously shown to have radioprotective effects. In both groups, three cycles resulted in increased albuminuria for each cycle, with large individual variation. Another marker of kidney injury, serum blood urea nitrogen (BUN), was only significantly increased compared to control animals after the third cycle. The number of white and red blood cells decreased significantly and did not reach the levels of control animals during the experiment. rA1M did reduce absorbed dose to kidney but did not show significant protection here, but future studies are warranted due to the recent clinical studies showing a significant renoprotective effect in patients.

Survival outcomes of radium-223 therapy for metastatic castration-resistant prostate cancer following national health insurance reimbursement in Taiwan.

BACKGROUND: Radium-223 dichloride (Ra-223) prolongs overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) with symptomatic bone metastases. However, there is considerable variation in outcomes among individuals. We aimed to evaluate the prognostic determinants associated with patient survival following National Health Insurance (NHI) reimbursement for Ra-223 therapy in Taiwan. METHODS: Patients with mCRPC who underwent Ra-223 treatment at Taipei Veterans General Hospital were retrospectively enrolled. Each intravenous Ra-223 dose was administered at 55 kBq/kg at 4-week intervals. Clinical outcomes were obtained from medical records; potential prognostic factors for survival were assessed. Kaplan-Meier analysis was used to generate cumulative survival curves; between-group differences were evaluated using the Chi-squared test. Statistical significance was set at p < 0.05. RESULTS: Seventy-six patients underwent Ra-223 therapy; 62 patients received NHI reimbursement and the remainder self-paid. Fifty patients (65.8%) completed six cycles of treatment; 26 (34.2%) received 1 to 5 cycles. Mortality occurred in 47 patients. Factors significantly associated with survival included ≤five bone metastases ( p = 0.0018), baseline prostate-specific antigen (PSA) ≤36 ng/mL ( p = 0.0004), baseline alkaline phosphate (ALP) <115 U/L ( p = 0.0007), and baseline hemoglobin (Hb) >12 g/dL ( p = 0.0029). Patients who completed six cycles of treatment achieved significantly higher OS compared to those who did not ( p < 0.0001). There has been a 4.4-fold increase in the number of patients since reimbursement began; there was no significant difference in OS between patients who received NHI reimbursement and those who self-paid. CONCLUSION: Administration of Ra-223 demonstrates considerable potential to extend the survival of patients with mCRPC. Survival outcomes may be influenced by various prognostic factors. However, no significant difference in OS was observed subsequent to reimbursement of Ra-223 therapy for mCRPC through the NHI system in Taiwan.

A phase 2, single-arm trial evaluating 131 I-PSMA-1095 targeted radioligand therapy for metastatic castration-resistant prostate cancer.

BACKGROUND: Metastatic castration-resistant prostate cancer (mCRPC) remains uniformly lethal. Prostate specific membrane antigen (PSMA) is a transmembrane glycoprotein overexpressed in prostate cancer. 131 I-PSMA-1095 (also known as 131 I-MIP-1095) is a PSMA-targeted radioligand which selectively delivers therapeutic radiation to cancer cells and the tumor microenvironment. METHODS: We conducted a single-arm, phase 2 trial to assess efficacy and tolerability of 131 I-PSMA-1095 in mCRPC patients who had exhausted all lines of approved therapy. All patients underwent 18 F-DCFPyL PET and 18 F-FDG PET to determine PSMA-positive tumor volume, and patients with >50% PSMA-positive tumor volume were treated with up to four doses of 131 I-PSMA-1095. The primary endpoint was the response rate of prostate specific antigen (PSA). Secondary endpoints included rates of radiographic response and adverse events. Overall and radiographic progression-free survival were also analyzed. RESULTS: Eleven patients were screened for inclusion and nine patients received 131 I-PSMA-1095. The median baseline PSA was 162 µg/l, and six patients demonstrated a >50% PSA decrease. One patient demonstrated a confirmed radiographic response. Median overall survival was 10.3 months, and median progression-free survival was 5.4 months. Four patients experienced adverse events of grade 3 or higher, the most frequent being thrombocytopenia and anemia. CONCLUSION: 131 I-PSMA-1095 is highly active against heavily-pretreated PSMA-positive mCRPC, significantly decreasing tumor burden as measured by PSA. Adverse events, mainly hematologic toxicity, were not infrequent, likely related to off-target irradiation. This hematologic toxicity, as well as a higher logistical burden associated with use, could represent relative disadvantages of 131 I-PSMA-1095 compared to 177 Lu-PSMA-617.

A Phase 0 Study to Assess the Biodistribution and Pharmacokinetics of a Radiolabeled Antibody Targeting Human Kallikrein 2 in Participants with Metastatic Castration-Resistant Prostate Cancer.

Despite the inclusion of multiple agents within the prostate cancer treatment landscape, new treatment options are needed to address the unmet need for patients with metastatic castration-resistant prostate cancer (mCRPC). Although prostate-specific membrane antigen is the only cell-surface target to yield clinical benefit in men with advanced prostate cancer, additional targets may further advance targeted immune, cytotoxic, radiopharmaceutical, and other tumor-directed therapies for these patients. Human kallikrein 2 (hK2) is a novel prostate-specific target with little to no expression in nonprostate tissues. This first-in-human phase 0 trial uses an 111In-radiolabeled anti-hK2 monoclonal antibody, [111In]-DOTA-h11B6, to credential hK2 as a potential target for prostate cancer treatment. Methods: Participants with progressive mCRPC received a single infusion of 2 mg of [111In]-DOTA-h11B6 (185 MBq of 111In), with or without 8 mg of unlabeled h11B6 to assess antibody mass effects. Sequential imaging and serial blood samples were collected to determine [111In]-DOTA-h11B6 biodistribution, dosimetry, serum radioactivity, and pharmacokinetics. Safety was assessed within a 2-wk follow-up period from the time of [111In]-DOTA-h11B6 administration. Results: Twenty-two participants received [111In]-DOTA-h11B6 and are included in this analysis. Within 6-8 d of administration, [111In]-DOTA-h11B6 visibly accumulated in known mCRPC lesions, with limited uptake in other organs. Two treatment-emergent adverse events unrelated to treatment occurred, including tumor-related bleeding in 1 patient, which led to early study discontinuation. Serum clearance, biodistribution, and tumor targeting were independent of total antibody mass (2 or 10 mg). Conclusion: This first-in-human study demonstrates that tumor-associated hK2 can be identified and targeted using h11B6 as a platform as the h11B6 antibody selectively accumulated in mCRPC metastases with mass-independent clearance kinetics. These data support the feasibility of hK2 as a target for imaging and hK2-directed agents as potential therapies in patients with mCRPC.

A step toward simplified dosimetry of radiopharmaceutical therapy via SPECT frame duration reduction.

Despite being time-consuming, SPECT/CT data is necessary for accurate dosimetry in patient-specific radiopharmaceutical therapy. We investigated how reducing the frame duration (FD) during SPECT acquisition can simplify the dosimetry workflow for [177Lu]Lu-PSMA radioligand therapy (RLT). We aimed to determine the impact of shortened acquisition times on dosimetric precision. Three SPECT scans with FD of 20, 10, and 5 second/frame (sec/fr) were obtained 48 h post-RLT from one metastatic castration-resistant prostate cancer (mCRPC) patient's pelvis. Planar images at 4, 48, and 72 h post-therapy were used to calculate time-integrated activities (TIAs). Using accurate activity calibrations and GATE Monte Carlo (MC) dosimetry, absorbed doses in tumor lesions and kidneys were estimated. Dosimetry precision was assessed by comparing shorter FD results to the 20 sec/fr reference using relative percentage difference (RPD). We observed consistent calibration factors (CFs) across different FDs. Using the same CF, we obtained marginal RPD deviations less than 4% for the right kidney and tumor lesions and less than 7% for the left kidney. By reducing FD, simulation time was slightly decreased. This study shows we can shorten SPECT acquisition time in RLT dosimetry by reducing FD without sacrificing dosimetry accuracy. These findings pave the way for streamlined personalized internal dosimetry workflows.

Salivary toxicity from PSMA-targeted radiopharmaceuticals: What we have learned and where we are going.

Clinical trials of prostate-specific membrane antigen (PSMA) targeted radiopharmaceuticals have shown encouraging results. Some agents, like lutetium-177 [177Lu]Lu-PSMA-617 ([177Lu]Lu-PSMA-617), are already approved for late line treatment of metastatic castration-resistant prostate cancer (mCRPC). Projections are for continued growth of this treatment modality; [177Lu]Lu-PSMA-617 is being studied both in earlier stages of disease and in combination with other anti-cancer therapies. Further, the drug development pipeline is deep with variations of PSMA-targeting radionuclides, including higher energy alpha particles conjugated to PSMA-honing vectors. It is safe to assume that an increasing number of patients will be exposed to PSMA-targeted radiopharmaceuticals during the course of their cancer treatment. In this setting, it is important to better understand and mitigate the most commonly encountered toxicities. One particularly vexing side effect is xerostomia. In this review, we discuss the scope of the problem, inventories to better characterize and monitor this troublesome side effect, and approaches to preserve salivary function and effectively palliate symptoms. This article aims to serve as a useful reference for prescribers of PSMA-targeted radiopharmaceuticals, while also commenting on areas of missing data and opportunities for future research.

Dual FDG/PSMA PET imaging to predict lesion-based progression of mCRPC during PSMA-RLT.

Candidates for prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) of metastatic castration-resistant prostate cancer (mCRPC) frequently have "mismatch" lesions with pronounced 18-fluorodeoxyglucose ([18F]FDG) but attenuated PSMA ligand uptake on positron emission tomography (PET). However, no quantitative criteria yet exist to identify mismatch lesions and predict their response to RLT. To define such criteria, we retrospectively analyzed 267 randomly-selected glucometabolic mCRPC metastases from 22 patients. On baseline PET, we determined [18F]FDG and [68Ga]Ga-PSMA-11 maximum standardized uptake value (SUVmax), and calculated the [18F]FDG SUVmax/[68Ga]Ga-PSMA-11 SUVmax quotient (FPQ). From follow-up [18F]FDG PET after two lutetium-177-PSMA-617 RLT cycles, we evaluated the treatment response and categorized the lesions into three subgroups (partial remission, stable disease, progression) based on change in [18F]FDG SUVmax. Lastly, we compared the baseline PET variables in progressing versus non-progressing lesions. Variables differing significantly, and a score incorporating them, were assessed via receiver operator characteristic (ROC) curve analysis, regarding ability to predict lesional progression, with area under the curve (AUC) as metric. Cut-offs with optimal sensitivity and specificity were determined using the maximum value of Youden's index. Fifty-one of 267 lesions (19.1%) progressed, 102/267 (38.2%) manifested stable disease, and 114/267 (42.7%) partially responded after two RLT cycles. At baseline, median [68Ga]Ga-PSMA-11 SUVmax was significantly lower (p < 0.001), median FPQ significantly higher (p < 0.001), and median [18F]FDG SUVmax similar in progressing versus non-progressing lesions. [68Ga]Ga-PSMA-11 SUVmax and FPQ showed predictive power regarding progression (AUCs: 0.89, 0.90). An introduced clinical score combining both further improved predictive performance (AUC: 0.94). Optimal cut-offs to foretell progression were: [68Ga]Ga-PSMA-11 SUVmax < 11.09 (88.2% sensitivity, 81.9% specificity), FPQ ≥ 0.92 (90.2% sensitivity, 78.7% specificity), clinical score ≥ 6/9 points (88.2% sensitivity, 87.5% specificity). At baseline, a low [68 Ga]Ga-PSMA-11 SUVmax and a high FPQ predict early lesional progression under RLT; [18F]FDG SUVmax does not. A score combining [68 Ga]Ga-PSMA-11 SUVmax and FPQ predicts early lesional progression even more effectively and might therefore be useful to quantitatively identify mismatch lesions.

Safety and Efficacy of Extended Therapy with [177Lu]Lu-PSMA: A German Multicenter Study.

Prospective results have demonstrated favorable safety and efficacy of [177Lu]Lu-PSMA radiopharmaceutical therapy for up to 6 cycles in men with metastatic castration-resistant prostate cancer. However, no systematic data are available outlining the feasibility of extended therapy beyond 6 cycles. We aim to evaluate the safety and efficacy of extended [177Lu]Lu-PSMA radiopharmaceutical therapy in patients who have received more than 6 cycles. Methods: In total, 111 patients were included in this multicenter retrospective analysis. Based on individual decisions, patients underwent uninterrupted continuation of therapy (continuous treatment) or reexposure after a therapy break (rechallenge treatment) between 2014 and 2023. Overall survival, 50% prostate-specific antigen (PSA) decline (measured 8-12 wk after treatment initiation or rechallenge), PSMA PET response, and grades per Common Terminology Criteria for Adverse Events were assessed. χ2 tests, multivariable Cox regression analysis, and log-rank tests were applied for statistical analyses. Results: Patients received extended treatment with [177Lu]Lu-PSMA, either as a continuous treatment (43/111, 38.7%) or as a rechallenge (68/111, 61.3%) treatment, with median cumulative doses of 57.4 or 60.8 GBq, respectively. Overall survival from the initiation of [177Lu]Lu-PSMA was 31.3, 23.2, and 40.2 mo for the entire cohort, the continuous treatment group, and the rechallenge treatment group, respectively. The initial 50% PSA decline was significantly higher in the retreated group than in the continuous group (57/63 [90.4%] vs. 26/42 [61.9%]; P = 0.006). A 50% PSA decline was observed in 23 of 62 patients (37.1%) after the first rechallenge. The rate of grades 3-4 toxicity was comparable between continuous and rechallenge treatments (anemia, 7/43 [16.3%] vs. 13/68 [19.1%)], P = 0.6; leukocytopenia, 1/43 [2.3%] vs. 2/67 [3.0%], P = 0.3; thrombocytopenia, 3/43 [7.0%] vs. 3/68 [4.4%], P = 0.3; renal, 2/43 [4.7%] vs. 5/68 [7.4%], P = 0.2). Conclusion: Extended therapy with [177Lu]Lu-PSMA is safe and has not been associated with increased grades 3-4 toxicity. Patient candidates for extended treatment experienced a favorable median survival of 31.3 mo from the first administration. Response under [177Lu]Lu-PSMA rechallenge demonstrated preserved efficacy of [177Lu]Lu-PSMA after a treatment break.

Efficacy of Combination Therapy With Radium-223 and Enzalutamide in Castration-resistant Prostate Cancer With Bone Metastases.

BACKGROUND/AIM: Radium-223 therapy has been reported to improve prognosis in patients with castration-resistant prostate cancer (CRPC) and bone metastases. Occasionally, radium-223 and androgen receptor signaling inhibitors (ARSIs) are used in combination for disease control, but the efficacy of this combination is unclear. This study assessed the efficacy of the addition of enzalutamide in patients treated with radium-223. PATIENTS AND METHODS: We included patients with CRPC and bone metastases who were treated with radium-223 at our institution. Patients were assigned to the enzalutamide combination group or non-combination group. We compared progression-free survival (PFS), overall survival (OS), and the completion rate of radium-223 between the two groups. RESULTS: In total, 39 patients with CRPC were included in this retrospective study. The median follow-up duration was 8.8 months. The enzalutamide combination and non-combination groups included 22 (56.4%) and 17 patients (43.6%), respectively. Median PFS was 11.3 months [95% confidence interval (CI)=3.9-19.9] in the combination group, versus 3.0 months (95%CI=1.9-5.5) in the non-combination group (p=0.004). Median OS did not significantly differ between the groups. The radium-223 completion rate was higher in the combination group than in the non-combination group (72.7% vs. 35.3%, p=0.026). CONCLUSION: The combined use of enzalutamide with radium-223 therapy improved PFS and treatment completion rates in patients with CRPC and bone metastases. This combination may be associated with a more favorable prognosis.

Increase of prostate-specific antigen doubling time predicts survival in metastatic castration-resistant prostate cancer patients undergoing radium therapy.

OBJECTIVE: Radium-223 (Ra-223) is an important treatment modality for bone-dominant metastatic castration-resistant prostate cancer (mCRPC). However, there is currently a lack of effective markers to monitor treatment response during treatment. We aim to investigate the response in prostate-specific antigen doubling time (PSADT) as a potential marker for assessing Ra-223 treatment in mCRPC patients. METHODS: We retrospectively collected data from mCRPC patients who underwent radium treatment at our institution between August 2020 and June 2023. Prostate-specific antigen (PSA) measurements prior to treatment and during treatment were collected. Baseline PSADT was calculated from PSA measurements prior to Ra-223 treatment; interim PSADT was calculated from PSA measurements before Ra-223 treatment and prior to the fourth course injection. Overall survival was calculated from the start of treatment to the date of death. Univariable and multivariable analysis using the Cox proportional hazards model were performed to examine the association of factors with overall survival. RESULTS: We included 35 patients from our institution, with a median overall survival of 13.3 months. Eighteen (51.4%) completed all six courses of treatment. PSA dynamic response (interim PSADT > baseline PSADT or decreased PSA) was observed in 20 patients. Overall survival was associated with a PSA dynamic response (HR = 0.318, 95% CI 0.133-0.762, p = 0.010) when compared to patients without response. CONCLUSIONS: Dynamic changes in PSADT were associated with survival in mCRPC patients receiving radium therapy. Comparing interim and baseline PSADT could serve as a valuable marker for determining treatment benefits.

Current state of theranostics in metastatic castrate-resistant prostate cancer.

Prostate cancer remains one of the leading causes of cancer-related death in the world. There have been significant advances in chemotherapy, hormonal therapy and targeted therapy options for patients with castrate-resistant disease. However, these systemic treatments are often associated with unwanted toxicities. Targeted therapy with radiopharmaceuticals has become of key interest to limit systemic toxicity and provides a more precision oncology approach to treatment. Strontium-89, Samarium-153 EDTMP and Radium-223 have been trialled with mixed results. Strontium-89 and Samarium-153 EDTMP have shown benefits in palliating metastatic bone pain but with no impact on survival outcomes. Early therapeutic radiopharmaceuticals targeting PSMA that were developed were beta-emitting agents, but recently alpha-emitting agents are being investigated as potentially superior options. Radium-223 is the first alpha-particle emitter therapeutic agent approved by the FDA, with phase III trial evidence showing benefits in overall survival and delay in symptomatic skeletal events for patients. Recently, 177-Lutetium-PSMA-617 has demonstrated significant survival advantages in pre-treated metastatic castrate-resistant cancer patients in a number of phase II and III studies. Furthermore, 225-Actinium-PSMA-617 also showed promise even in patients pre-treated with 177-Lutetium-PSMA-617. Hence, there has been an explosion of radiopharmaceutical treatment options for patients with prostate cancer. This review explores past and current theranostic capacities in the radiopharmaceutical treatment of metastatic castrate-resistant prostate cancer.