Metastatic Castration-resistant Prostate Carcinoma Research Articles

A Comparison of 68Ga-PSMA PET/CT-Based Split Renal Function with 99mTc-MAG3 Renography in Patients with Metastatic Castration-Resistant Prostate Carcinoma Treated with 177Lu-PSMA.

Physiological PSMA expression in the cells of the proximal renal tubules and consecutive radiopharmaceutical binding and retention could potentially lead to radioligand-therapy-induced nephrotoxicity. Thus, patients with metastatic castration-resistant prostate cancer undergo 99mTc-Mercaptoacetyltriglycine (MAG3) renal scintigraphy to assess kidney function and to exclude renal obstruction as part of their workup for PSMA-targeted radioligand therapy (RLT). 99mTc-MAG-3 renal scintigraphy often requires an additional visit to the nuclear medicine department and patients spend 30-90 min in the department, which is inconvenient and takes up camera time. In addition, the patients are subjected to a baseline 68Ga-PSMA PET/CT to assess for PSMA-positive disease prior to targeted radioligand therapy. The aim of this retrospective cross-sectional study was to compare 99mTc-MAG-3-based split renal function (SRF) with 68Ga-PSMA-derived SRF. This retrospective cross-sectional study included 28 patients with histologically proven metastatic castration-resistant prostate cancer (mCRPC) who received 177Lu-PSMA617. A comparison between the split renal function using 68Ga-PSMA PET/CT and the 99mTc-MAG-3-derived split renal function was carried out in 56 kidneys (n = 56). The SRF on 68Ga-PSMA was calculated using the volume and the average standard uptake value (SUVmean) within each VOI calculated as previously described by Roser et al.: SRF = (VOLUMEright) ∗ SUVmeanright/(VOLUMEright ∗ SUVmeanright + VOLUMEleft ∗ SUVmeanleft). Paired tests and correlation coefficients were used to compare 68Ga-PSMA and 99mTc-MAG-3. A visual comparison of kidney morphology on both studies was also performed. The median SRF of the right kidney was 49.9% (range: 3-91%) using 68Ga-PSMA PET/CT and 50.5% (range: 0-94%) with 99mTc-MAG3 scintigraphy. Notably, there was a strong correlation between SRF measurements obtained from PSMA and 99mTcMAG3, with a Pearson correlation coefficient of 0.957 (p < 0.001). Both 99mTc-MAG3 and 68Ga-PSMA PET/CT studies identified morphological renal abnormalities; there were nine hydronephrotic kidneys, four shrunken kidneys and one obstructed kidney, and there was a strong positive correlation between 68Ga-PSMA kidney morphology and 99mTcMAG3 renal scintigraphy kidney morphology, with a correlation coefficient of 0.93. PSMA-derived split function demonstrated a high correlation with renal function assessed on diuretic 99mTc-MAG3 renograms. PET-derived split renal function may, therefore, be considered an alternative to diuretic renogram-based split function. Furthermore, both 99mTc-MAG3 and 68Ga-PSMA PET/CT studies identified morphological renal abnormalities such as hydronephrosis, shrunken and obstructed kidneys. This correlation underscores the potential utility of 68Ga-PSMA imaging as a valuable tool for assessing kidney morphology as an alternative to renogram split function in clinical practice.

Differentiation of Discordant Lesions on Dual-Tracer PET/CT (68Ga-PSMA-11 and 18F-FDG) in Prostate Carcinoma: Diagnosis of Second Primary Malignancies.

We present 2 cases of metastatic castration-resistant prostate carcinoma with discordant lesions on dual-tracer PET/CT (68Ga-PSMA-11 and 18F-FDG PET/CT), which on subsequent histopathologic evaluation revealed second primary malignancies of combined hepatocellular carcinoma and cholangiocarcinoma and poorly differentiated squamous cell carcinoma. These case illustrations emphasize the need to evaluate discordant lesions on dual-tracer PET/CT, which can lead to early diagnosis of second primary malignancies and thereby can provide better management in these patients.

Efficacy of PARP inhibitors in patients with metastatic castration resistant prostate carcinoma: A meta-analysis of phase III randomized controlled trials.

e17060 Background: PARP inhibitors effectively treat several solid tumors, regardless of the presence of BRCA mutations. Patients with castration-resistant metastatic prostate cancer become refractory to androgen deprivation therapy. PARP inhibitors were recently approved for use in prostate cancer, and have opened new avenues in prostate cancer treatment research. Methods: We systematically searched multiple databases using pre-specified search terms. We included only phase III RCTs comparing PARP inhibitors versus standard of care in patients with castration-resistant biopsy-proven metastatic prostate cancer. The outcomes studied were radiologically guided progression-free survival (PFS) and overall survival (OS). We used a random effects model via RevMan 5.4 software for statistical analysis. Results: 3 phase III RCTs met the inclusion criteria with a total of 1606 patients (PARP inhibitors = 867 patients, standard of care = 739 patients). Compared to the standard of care, PARP inhibitors showed significantly higher PFS [HR = 0.62( 95% CI, 0.49-0.78) P &lt; 0.0001]. There was no statistically significant difference in OS [HR = 0.85( 95% CI, 0.69-0.1.04) P = 0.11] between the two groups. Conclusions: The use of PARP inhibitors in patients with castration-resistant metastatic prostate cancer is associated with improved progression-free survival. No significant difference was observed in overall survival between the two groups. There is a need to study the cost-benefit analysis of using PARP inhibitors as they do not show any improvement in overall survival. [Table: see text]

Clinical development of the bispecific PSMAxCD3 antibody CC-1.

2534 Background: While being highly efficient in hematological malignancies, bispecific antibodies (bsAbs), alike CAR T cells, are yet not successful in solid tumors. Moreover, all available T cell-mobilizing strategies cause side effects that endanger patients and, in case of bsAbs, limit applicable doses and thus efficacy. We report on the clinical development of CC-1, a PSMAxCD3 bsAb, in an IgG-based format that induces fully target cell-restricted T cell activity (Zekri et al, EMBO Mol Med, 2020). Targeting PSMA, which is expressed on malignant cells and on the neovasculature, improves accessibility of the tumor site for immune effector cells as critical prerequisite for success in solid tumors. Notably, CC-1 binds a unique PSMA epitope which is expressed on malignant cells both of prostate carcinoma (PC) and 50% of patients with squamous cell carcinoma (SCC) of the lung. Methods: A FIH trial evaluating CC-1 with pre-emptive Tocilizumab included patients with metastatic castration resistant prostate carcinoma (mCRPC) (NCT04104607) and consisted of two parts. Dose escalation (n=10-66) using a novel intra-individual dose escalation design to rapidly reach the target dose of 826µg to determine safety, tolerability and maximum tolerated dose (MTD) (Labrenz et al, Pharm Stat, 2022). The dose expansion cohort exposed patients to CC-1 at MTD and explored efficacy to define RP2D (n=14). Our second phase I trial enrolls patients with SCC of the lung (NCT04496674) to receive CC-1 in combination with checkpoint inhibition. Based on the meanwhile available very favorable safety and preliminary efficacy data, a third phase I trial was initiated where CC-1 is evaluated as first line treatment in patients with hormone sensitive biochemical recurrence (BCR) of PC (NCT05646550), where tumor burden is low and accordingly lower side effects and long-lasting efficacy are expected. Results: Recruitment in the dose escalation part of the trial in mCRPC has been completed and the target dose was reached and MTD defined without DLT upon treatment of the 9th and 14th patient, respectively. 24 patients completed treatment, with the most frequently observed toxicity being cytokine release syndrome (CRS, max. 2°) (88%). Besides grade 1 to 2 hypertension (46%) and xerostomia (8%), no further CC-1 related toxicities were observed. A rapid and profound decline of elevated PSA levels was observed in all but one patient, with up to 60% reduction compared to baseline. So far 5 patients received multiple treatment cycles at MTD-level. One patient with SCC of the lung has been treated and CC-1 was escalated up to 153µg without occurrence of CRS. In the phase I trial in BCR of PC, the first three patients were enrolled in February 2023. Conclusions: CC-1 is a promising compound with a favourable toxicity profile and promising clinical activity. Details on study designs and updated data from the 3 clinical trials will be presented at the meeting. Clinical trial information: NCT04104607 , NCT04496674 , NCT05646550 .

Lean Body Mass and Total Body Weight Versus Body Surface Area as a Determinant of Docetaxel Pharmacokinetics and Toxicity.

This study examined whether anthropometric and body composition parameters such as body surface area (BSA), lean body mass (LBM), and total body weight (TBW) are correlated with docetaxel clearance and exposure by analyzing area under the curve. In addition, LBM, TBW, and a fixed dose were compared with BSA as dosing parameters for dose individualization of docetaxel. Thirty-six patients receiving docetaxel chemotherapy for breast or metastatic castration-resistant prostate carcinoma were included. Before treatment, LBM was measured using a dual-energy X-ray absorptiometry scanner. Blood samples were collected up to 180 minutes after dosing to analyze docetaxel concentrations and determine individual pharmacokinetic parameters. No significant correlations were found between docetaxel clearance and the anthropometric and body composition variables (BSA, LBM, and TBW). The area under the curve was significantly but poorly correlated with BSA [r = 0.452 ( P = 0.016)] and TBW [r = 0.476 ( P = 0.011)]. The mean absolute percentage error and mean error of simulated dosing based on LBM and fixed dosing were not significantly different from those of BSA. For TBW, only mean absolute percentage error was significantly higher compared with dosing based on BSA (24.1 versus 17.1, P = 0.001). There was no clinically relevant correlation between docetaxel pharmacokinetics and the anthropometric and body composition variables BSA, LBM, and TBW. Therefore, dose individualization of docetaxel based on LBM, TBW, or fixed dosing cannot be recommended over BSA-based dosing.

Current Trends in Advanced Prostate Cancer Medical Setting

Abstract Treatment of advanced and metastatic prostate carcinoma (PCa) is still challenging and changing in the era of personalised medicine. Combination therapies with docetaxel and new anti-hormonal substances lead to improved OS (overall survival) in a broad group of patients with metastatic hormone sensitive prostate carcinoma (mHSPCa). Addition of docetaxel or an androgen receptor targeting agent (ARTA) with abiraterone plus prednisolone, with apalutamide or with enzalutamide leads to a significant improvement in OS and an increase in the time to transition to castration resistance. The choice of therapy sequence in advanced PCa should be based, among other things, on the side-effect profiles of the substances and patient’s preferences. Within metastatic castration resistant prostate carcinoma (mCRPCa) setting, the therapy with abiraterone, enzalutamide, docetaxel, cabazitaxel and radium-223 is approved and indicated in Europe. Respectively, five substances are available, each of which has led to a significant increase in survival time in phase III studies. The optimal therapy sequence in the mCRPCa stage is still unclear. The current trend in personalised medicine in the next decade in therapy, regarding prostate carcinoma, are poly(ADP)-ribose polymerase (PARP) inhibitors, which are and will be available as an effective therapy option for patients with mutations in DNA repair genes. The most important question is when and how patients should be tested for mutations in DNA repair genes and to which line of therapy will PARP inhibitors belong.

MCRPC Patients Receiving 225Ac-PSMA-617 Therapy in the Post-Androgen Deprivation Therapy Setting: Response to Treatment and Survival Analysis.

225Ac-PSMA-617, targeting the prostate-specific membrane antigen (PSMA), which is overexpressed on prostate cancer cells, has shown a remarkable therapeutic efficacy in heavily pretreated patients with metastatic castration-resistant prostate carcinoma (mCRPC). Here, we report on treatment outcome and survival using this novel treatment modality in a series of 53 patients with mCRPC directly after their androgen deprivation treatment (ADT). Methods: 225Ac-PSMA-617 was administered to 53 such patients. 68Ga-PSMA PET/CT was obtained at baseline, before every treatment cycle, and on follow-up to select patients for treatment, determine the activity to be administered, and assess their response. Serial prostate-specific antigen (PSA) measurements were obtained for response assessment. Results: The median age of the patients was 63.4 y (range, 45-83 y). In total, 167 cycles were administered (median, 3; range, 1-7). Forty-eight patients (91%) had a PSA decline of at least 50%, and 51 patients (96%) had any decline in PSA. 68Ga-PSMA PET findings became negative in 30 patients. In the multivariate analysis, a PSA decline of at least 50% proved predictive of both progression-free survival (PFS) and overall survival (OS), and platelet count also proved predictive for PFS. The median estimated OS was 9 mo for patients with a PSA decline of less than 50% but was not yet reached at the latest follow-up (55 mo) for patients with a PSA decline of 50% or more. The estimated median PFS was 22 mo for patients with a PSA decline of at least 50% and 4 mo for patients with a PSA decline of less than 50%. No severe hematotoxicity was noted, and only 3 patients had grade III-IV nephrotoxicity. The commonest toxicity seen was grade I-II xerostomia, observed in 81% of patients. Conclusion: In 91% of 53 patients with mCRPC, treatment with 225Ac-PSMA-617 immediately after ADT resulted in at least a 50% decrease in PSA level. Furthermore, a PSA decline of at least 50% proved the single most important factor predicting PFS and OS after 225Ac-PSMA-617 treatment. Of interest, median OS in patients with a PSA decline of at least 50% was not yet reached at the latest follow-up (55 mo). These favorable results suggest that it would be of major clinical relevance to perform a prospective randomized study comparing 225Ac-PSMA-617 with current standard-of-care treatment options such as enzalutamide, abiraterone acetate, and docetaxel after ADT.

Preparation of 177Lu-PSMA-617 in Hospital Radiopharmacy: Convenient Formulation of a Clinical Dose Using a Single-Vial Freeze-Dried PSMA-617 Kit Developed In-House.

Objective In the recent time, endoradionuclide therapy for metastatic castration-resistant prostate carcinoma employing 177Lu-PSMA-617 has yielded encouraging results and several clinical trials with the agent are currently ongoing. Routine preparation of 177Lu-PSMA-617 patient doses can be made simpler and convenient, if the ingredients essential for radiolabeling are made available in a ready-to-use lyophilized form. Methods PSMA-617 freeze-dried kit was formulated and used for the preparation of 177Lu-PSMA-617 clinical dose with high radiochemical purity using low/medium specific activity 177Lu. Detailed radiochemical studies were performed to determine the maximum activity and volume of 177LuCl3, which can be added in the kit for the formulation of 177Lu-PSMA-617. Studies were also performed to determine the shelf life of the kit to ensure its long-term usage. Studies were performed in buffer as well as human serum medium to determine the stability of the 177Lu-PSMA-617 complex after storing in respective media up to 7 days postpreparation. About ten patient doses of 177Lu-PSMA-617 were administered, and posttherapy scans were acquired. Results The formulated freeze-dried kit of PSMA-617 could be radiolabeled with an average percentage radiochemical purity > 98.53 ± 0.38. The freeze-dried kit was found suitable for tolerating up to 0.5 mL of 177LuCl3 (in 0.01 N HCl) and specific activity of 555 MBq/μg (15 mCi/μg) for the preparation of the patient dose of 177Lu-PSMA-617. The 177Lu-PSMA-617 complex prepared using the freeze-dried kit of PSMA-617 was observed to maintain % radiochemical purity (RCP) of 96.74 ± 0.87 and 94.81 ± 2.66, respectively, even after storing up to 7 days in buffer and human serum, respectively. 177Lu-PSMA-617 prepared using the in-house formulated freeze-dried kit of PSMA-617 exhibited accumulation in metastatic lesions picked up in a pretherapy PET scan. Reduction in number as well as size of lesions was observed in posttherapy scans acquired after two months of administering the first therapeutic dose of 177Lu-PSMA-617. Conclusions The freeze-dried kit of PSMA-617 could be used for the preparation of 177Lu-PSMA-617 with high radiochemical purity (>98%) in a reproducible manner. 177Lu-PSMA-617 prepared using the developed kit was successfully evaluated in patients suffering from metastatic prostate cancer.

Renal Safety of [177Lu]Lu-PSMA-617 Radioligand Therapy in Patients with Compromised Baseline Kidney Function.

Simple SummaryRadioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) is an effective antitumor-treatment in metastatic castration-resistant prostate carcinoma (mCRPC). Concerns of potential nephrotoxicity are based on renal tubular PSMA expression and the resulting radiopharmaceutical retention during RLT, but data confirming clinically significant renal toxicity are still lacking. In this study, n = 22 patients treated within a prospective patient registry (REALITY Study) with significantly impaired baseline kidney function were investigated for treatment-associated nephrotoxicity and the potential relationship with administered activities of [177Lu]Lu-PSMA-617. As opposed to prevailing concerns, glomerular filtration rate (GFR) improved significantly in our cohort of patients and no significant correlation between change in GFR and administered activities were found. As pre-treatment chronic kidney failure did not lead to detectable RLT-induced deterioration of renal function in our study, the nephrotoxic potential of [177Lu]Lu-PSMA-617 RLT may be overestimated. We suggest not to categorically exclude patients from enrolment to PSMA-RLT due to renal impairment.Background: Radioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) is an effective antitumor-treatment in metastatic castration-resistant prostate carcinoma (mCRPC). Concerns of potential nephrotoxicity are based on renal tubular PSMA expression and the resulting radiopharmaceutical retention during RLT, but data confirming clinically significant renal toxicity are still lacking. In this study, patients with significantly impaired baseline kidney function before initiation of therapy were investigated for treatment-associated nephrotoxicity and the potential relationship with administered activities of [177Lu]Lu-PSMA-617. Methods: Twenty-two mCRPC patients with impaired renal function (glomerular filtration rate (GFR) ≤ 60 mL/min) who received more than two cycles of [177Lu]Lu-PSMA-617 RLT (median 5 cycles and median 6-week time interval between consecutive cycles) were analyzed in this study. Patients were treated within a prospective patient registry (REALITY Study, NCT04833517). Cumulative administered activities ranged from 17.1 to 85.6 GBq with a median activity of 6.5 GBq per cycle. Renal function was closely monitored during and after PSMA-RLT. Results: Mean pre-treatment GFR was 45.0 ± 10.7 mL/min. After two (22/22 patients), four (20/22 patients), and six cycles (10/22 patients) of RLT, a significant increase of GFR was noted (each p < 0.05). End-of-treatment GFR (54.1 ± 16.7 mL/min) was significantly higher than baseline GFR (p = 0.016). Only one patient experienced deterioration of renal function (change of CTCAE grade 2 to 3). The remaining patients showed no significant reduction of GFR, including follow-up assessments (6, 9, and 12 months), and even showed improved (10/22 patients) or unchanged (11/22 patients) CTCAE-based renal impairment grades during and after the end of PSMA-RLT. No significant correlation between the change in GFR and per-cycle (p = 0.605) or cumulative (p = 0.132) administered activities were found. Conclusions: As pre-treatment chronic kidney failure did not lead to detectable RLT-induced deterioration of renal function in our study, the nephrotoxic potential of [177Lu]Lu-PSMA-617 RLT may be overestimated and not of clinical priority in the setting of palliative treatment in mCRPC. We suggest not to categorically exclude patients from enrolment to PSMA-RLT due to renal impairment.

Efficacy and Safety of [225Ac]Ac-PSMA-617 Augmented [177Lu]Lu-PSMA-617 Radioligand Therapy in Patients with Highly Advanced mCRPC with Poor Prognosis.

The use of 225Ac in prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT), either as monotherapy or in combination with 177Lu, is a promising therapy approach in patients with metastatic castration-resistant prostate carcinoma (mCRPC). In this study, we report the efficacy and safety of [225Ac]Ac-PSMA-617 augmented [177Lu]Lu-PSMA-617 RLT in 177Lu-naive mCRPC patients (n = 15) with poor prognosis (presence of visceral metastases, high total tumor burden with diffuse bone metastases or a short PSA doubling time of <2 months). Biochemical (by PSA serum value) and molecular imaging response (by [68Ga]Ga-PSMA-11 PET/CT) was assessed after two cycles of [177Lu]Lu-PSMA-617 RLT, with at least one [225Ac]Ac-PSMA-617 augmentation. In addition, PSA-based progression-free survival (PSA-PFS), overall survival (OS) and toxicity (according to CTCAE) were analyzed. We observed a biochemical- and molecular imaging-based partial remission in 53.3% (8/15) and 66.7% (10/15) of patients, respectively. The median PSA-PFS and OS was 9.1 and 14.8 months, respectively. No serious acute adverse events were recorded. Two out of fifteen patients experienced grade 3 anemia. No other grade 3/4 toxicities were observed. RLT-related xerostomia (grade 1/2) was recorded in 2/15 patients. Our data showed a high clinical efficacy with a favorable side effects profile of [225Ac]Ac-PSMA-617 augmented [177Lu]Lu-PSMA-617 RLT in this highly challenging patient cohort.

Concept proposal for a six-tier integrated dual tracer PET-CT (68Ga-PSMA and FDG) image scoring system ('Pro-PET' score) and examining its potential implications in metastatic castration-resistant prostate carcinoma theranostics and prognosis.

To develop and examine a scoring system in metastatic castration-resistant prostate carcinoma (mCRPC) that integrates findings of both 68Ga-prostate-specific membrane antigen (PSMA) and flurodeoxyglucose (FDG) PET-CT imaging in a single combined parameter and referred to as the 'Pro-PET' score. A six-tier integrated dual tracer PET-CT (68Ga-PSMA and FDG) Image Scoring System ('Pro-PET' score) was conceptualized, based on the findings of both 68Ga-PSMA-11 and FDG PET-CT in patients of mCRPC. This proposed integrated scoring was examined in a retrospective analytical study assessing mCRPC patients (n = 47) referred for 177Lu-PSMA-617 peptide receptor radioligand therapy (PRLT) and had both FDG and 68Ga-PSMA PET-CT undertaken within 15 days of each other without any interim treatment intervention. The 'Pro-PET' score grades and subgrades were assigned and compared with clinical data, such as histopathology, Gleason score, serum prostate-specific antigen (PSA), treatment response (symptomatic, biochemical, metabolic and anatomical) and survival [overall survival (OS) and progression-free survival (PFS)]. The Pro-PET score significantly correlated with symptomatic (P = 0.05), biochemical (P = 0.05), metabolic (P = 0.001) and anatomical (P = 0.012) responses, PFS (P = 0.03) and OS (P = 0.027). On multivariate analysis, histopathology, Gleason score and PSA as individual parameters were not significantly associated with OS and PFS, whereas the Pro-PET score was found to have a significant association (P = 0.001 for PFS and 0.011 for OS). The 'Pro-PET' scoring system integrating dual tracer PET-CT imaging findings in a single parameter appeared as a potentially promising prognostic marker that has the potential to enhance the objectivity and scientific basis of prostate carcinoma theranostics and prognostication.

Molecular imaging and biochemical response assessment after a single cycle of [225Ac]Ac-PSMA-617/[177Lu]Lu-PSMA-617 tandem therapy in mCRPC patients who have progressed on [177Lu]Lu-PSMA-617 monotherapy.

Rationale: Despite the promising results of prostate-specific membrane antigen (PSMA)-targeted 177Lu radioligand therapy in metastatic castration-resistant prostate carcinoma (mCRPC), some patients do not respond and other patients with initially good response develop resistance to this treatment. In this study, we investigated molecular imaging and biochemical responses after a single cycle of [225Ac]Ac-PSMA-617/[177Lu]Lu-PSMA-617 tandem therapy in patients who had progressed on [177Lu]Lu-PSMA-617 monotherapy.Methods: Seventeen patients with mCRPC were included in a retrospective, monocenter study. Molecular imaging-based response was assessed by modified PERCIST criteria using the whole-body total lesion PSMA (TLP) and molecular tumour volume (MTV) derived from [68Ga]Ga-PSMA-11 PET/CT. Biochemical response was evaluated according to PCWG3 criteria using the prostate-specific antigen (PSA) serum value. Concordance and correlation statistics as well as survival analyses were performed.Results: Based on the molecular imaging-based response assessment, 5 (29.4%) patients showed partial remission and 7 (41.2%) had stable disease. The remaining 5 (29.4%) patients had further progression, four with an increase in TLP/MTV of >30% and one with stable TLP/MTV but appearance of new metastases. Based on the biochemical response assessment, 5 (29.4%), 8 (47.1%), and 4 (23.5%) patients showed partial remission, stable disease, and progressive disease, respectively. A comparison of the response assessment methods showed a concordance of 100% (17/17) between TLP and MTV and 70.6% (12/17) between TLP/MTV and PSA. Patients with partial remission, independently assessed by each method, had better overall survival (OS) than patients with either stable or progressive disease. The difference in OS was statistically significant for the molecular imaging response assessment (median OS not reached vs. 8.3 m, p = 0.044), but not for the biochemical response assessment (median OS 18.1 m vs. 9.4 m, p = 0.468).Conclusion: Based on both assessment methods, [225Ac]Ac-PSMA-617/[177Lu]Lu-PSMA-617 tandem therapy is an effective treatment for the highly challenging cohort of patients with mCRPC who have progressed on [177Lu]Lu-PSMA-617 monotherapy. Molecular imaging response and biochemical PSA response were mostly concordant, though a considerable number of cases (29.4%) were discordant. Molecular imaging response reflecting the change in total viable tumour burden appears to be superior to PSA change in estimating survival outcome after tandem therapy.

Biodistribution and post-therapy dosimetric analysis of [177Lu]Lu-DOTAZOL in patients with osteoblastic metastases: first results

BackgroundPreclinical biodistribution and dosimetric analysis of [177Lu]Lu-DOTAZOL suggest the bisphosphonate zoledronate as a promising new radiopharmaceutical for therapy of bone metastases. We evaluated biodistribution and normal organ absorbed doses resulting from therapeutic doses of [177Lu]Lu-DOTAZOL in patients with metastatic skeletal disease.MethodFour patients with metastatic skeletal disease (age range, 64–83 years) secondary to metastatic castration-resistant prostate carcinoma or bronchial carcinoma were treated with a mean dose of 5968 ± 64 MBq (161.3 mCi) of [177Lu]Lu-DOTAZOL. Biodistribution was assessed with serial planar whole body scintigraphy at 20 min and 3, 24, and 167 h post injection (p.i.) and blood samples at 20 min and 3, 8, 24, and 167 h p.i. Percent of injected activity in the blood, kidneys, urinary bladder, skeleton, and whole body was determined. Bone marrow self-dose was determined by an indirect blood-based method. Urinary bladder wall residence time was calculated using Cloutier’s dynamic urinary bladder model with a 4-h voiding interval. OLINDA/EXM version 2.0 (Hermes Medical Solutions, Stockholm, Sweden) software was used to determine residence times in source organs by applying biexponential curve fitting and to calculate organ absorbed dose.ResultsQualitative biodistribution analysis revealed early and high uptake of [177Lu]Lu-DOTAZOL in the kidneys with fast clearance showing minimal activity by 24 h p.i. Activity in the skeleton increased gradually over time. Mean residence times were found to be highest in the skeleton followed by the kidneys. Highest mean organ absorbed dose was 3.33 mSv/MBq for osteogenic cells followed by kidneys (0.490 mSv/MBq), red marrow (0.461 mSv/MBq), and urinary bladder wall (0.322 mSv/MBq). The biodistribution and normal organ absorbed doses of [177Lu]Lu-DOTAZOL are consistent with preclinical data.Conclusion[177Lu]Lu-DOTAZOL shows maximum absorbed doses in bone and low kidney doses, making it a promising agent for radionuclide therapy of bone metastasis. Further studies are warranted to evaluate the efficacy and safety of radionuclide therapy with [177Lu]Lu-DOTAZOL in the clinical setting.

Prostate carcinoma cell-derived exosomal MicroRNA-26a modulates the metastasis and tumor growth of prostate carcinoma

Prostate carcinoma may develop into metastatic castration-resistant prostate carcinoma (mCRPC) after endocrine therapy. Exosomal microRNAs play an important role in the regulation of tumor microenvironment. Our study aimed to investigate the effect of exosomal miR-26a on tumor phenotype of prostate carcinoma. Low-grade prostate carcinoma cell line (LNCAP) and mCRPC cell line (PC-3) were treated as experimental subjects according to their miR-26a expressions. Wound healing, transwell and colony-forming unit assays were performed after miR-26a mimic/inhibitor transfection. Then, exosomes were isolated from LNCAP and PC-3 cells, and the levels of exosomal miR-26a were determined. After co-culture of LNCAP (PC-3) cells with PC-3 (LNCAP) exosomes, changes in malignant behaviors were measured. Moreover, LNCAP/PC-3 exosomes were injected into xenograft tumor mice to determine effects of the exosomes on tumorigenicity of LNCAP and PC-3 cells. MiR-26a showed a potently inhibitory effect on cell proliferation, migration and invasion of LNCAP and PC-3 cells. LNCAP exosomes had a higher miR-26a level, compared with PC-3 exosomes. Overexpression of miR-26a attenuated the enhanced malignant behavior of LNCAP cells induced by PC-3 exosomes, and miR-26a inhibition could reverse the inhibitory effects of LNCAP exosomes on PC-3 cells. Exosomal miR-26a could significantly alter the expressions of epithelial-mesenchymal transition (EMT)-related factors. Moreover, LNCAP exosomes suppressed the tumorigenicity of PC-3 cells, while PC-3 exosomes could promote the tumorigenicity of LNCAP cells. Our data suggest that exosomal miR-26a derived from prostate carcinoma cells had a suppressive effect on the metastasis and tumor growth of prostate carcinoma.

Predictors of Overall and Disease-Free Survival in Metastatic Castration-Resistant Prostate Cancer Patients Receiving 225Ac-PSMA-617 Radioligand Therapy.

Metastatic prostate carcinoma overexpresses prostate-specific membrane antigen (PSMA), making this antigen a suitable target for radioligand therapy of the disease. Here we report on our experience with a series of 73 castration-resistant prostate carcinoma patients treated with 225Ac-PSMA-617, identifying variables predictive for overall survival (OS) and progression-free survival (PFS) after 225Ac-PSMA-617 treatment. Methods:225Ac-PSMA-617 was administered to patients who had metastatic castration-resistant prostate carcinoma and who had exhausted available therapy options for their disease. Full blood count, glomerular filtration rate, and liver function test were obtained at baseline and on follow-up for evaluation of toxicity. 68Ga-PSMA PET/CT was obtained at baseline, before every treatment cycle, and on follow-up for selection of patients for treatment, to determine the activity of the treatment agent to be administered, and for response assessment. Serial prostate-specific antigen (PSA) was obtained for PSA response assessment. Results: Seventy-three men (mean age, 69 y; range, 45-85 y) with metastatic castration-resistant prostate carcinoma were treated with 210 cycles of 225Ac-PSMA-617. In 70% of patients, a PSA decline of greater than or equal to 50% was obtained; 82% of patients had any PSA decline. In 29% of patients, all lesions on 68Ga-PSMA PET resolved in response to treatment. During follow-up, 23 patients experienced disease progression, whereas 13 patients died from their disease. The estimated median PFS and OS were 15.2 mo (95% CI, 13.1-17.4) and 18 mo (95% CI, 16.2-19.9), respectively. In univariate analyses, factors such as baseline PSA, any PSA decline, PSA decline of greater than or equal to 50%, prior chemotherapy, prior radiation therapy, and baseline hemoglobin level were associated with longer PFS and OS (all Ps < 0.05). In multivariate analyses, there was a negative association between prior 177Lu-PSMA therapy and PFS, and a positive association between PSA decline of greater or equal to 50% and PFS. Only a PSA decline of greater than or equal to 50% remained significantly associated with OS on multivariate analyses. Xerostomia was seen in 85% of patients but was not severe enough to warrant discontinuing treatment. Anemia was seen in 27 patients; no patients had grade IV bone marrow toxicity. Renal failure of grade III or IV was seen in 5 patients with baseline renal impairment. Conclusion: In this study, a PSA decline of greater than or equal to 50% after treatment with 225Ac-PSMA-617 was proven by multivariate analyses to be significantly associated with OS and PFS. Furthermore, previous 177Lu-PSMA treatment was negatively associated with PFS in both univariate and multivariate analyses.

Prediction of Normal Organ Absorbed Doses for [177Lu]Lu-PSMA-617 Using [44Sc]Sc-PSMA-617 Pharmacokinetics in Patients With Metastatic Castration Resistant Prostate Carcinoma.

Pharmacokinetics of [Sc]Sc-PSMA-617 was evaluated in 5 patients with metastatic castration-resistant prostate carcinoma using dynamic PET/CT, followed by 3 static PET/CT acquisitions and blood sample collection over 19.5 hours, as well as urine sample collection at 2 time points. Total activity measured in source organs by PET imaging, as well as counts per milliliter measured in blood and urine samples, was decay corrected back to the time of injection using the half-life of Sc. Afterward, forward decay correction using the half-life of Lu was performed, extrapolating the pharmacokinetics of [Sc]Sc-PSMA-617 to that of [Lu]Lu-PSMA-617. Source organs residence times and organ-absorbed doses for [Lu]Lu-PSMA-617 were calculated using OLINDA/EXM software. Bone marrow self-dose was determined with indirect blood-based method, and urinary bladder contents residence time was estimated by trapezoidal approximation. The maximum permissible activity of [Lu]Lu-PSMA-617 was calculated for each patient considering external beam radiotherapy toxicity limits for radiation absorbed doses to kidneys, bone marrow, salivary glands, and whole body. The predicted mean organ-absorbed doses were highest in the kidneys (0.44 mSv/MBq), followed by the salivary glands (0.23 mSv/MBq). The maximum permissible activity was highly variable among patients; limited by whole body-absorbed dose (1 patient), marrow-absorbed dose (1 patient), and kidney-absorbed dose (3 patients). [Sc]Sc-PSMA-617 PET/CT imaging is feasible and allows theoretical extrapolation of the pharmacokinetics of [Sc]Sc-PSMA-617 to that of [Lu]Lu-PSMA-617, with the intent of predicting normal organ-absorbed doses and maximum permissible activity in patients scheduled for therapy with [Lu]Lu-PSMA-617.

[44Sc]Sc-PSMA-617 Biodistribution and Dosimetry in Patients With Metastatic Castration-Resistant Prostate Carcinoma.

[Sc]Sc-PSMA-617 with 3.9-hour half-life, in vitro and in vivo characteristics similar to [Lu]Lu-PSMA-617 and possibility of delayed imaging after 24 hours or later, implies it to be advantageous than [ Ga]Ga-PSMA-617 for pretherapeutic dosimetric assessment for [Lu]Lu-PSMA-617 in metastatic castration-resistant prostate carcinoma (mCRPC) patients. In this study, we investigated biodistribution and radiation exposure to normal organs with [Sc]Sc-PSMA-617 in mCRPC patients. Five mCRPC patients (mean age, 69 years) enrolled for [Lu]Lu-PSMA-617 therapy were injected with 40-62 MBq [Sc]Sc-PSMA-617 intravenously; Siemens Biograph 2 PET/CT system was used to acquire dynamic PET data (30 minutes) in list mode over the abdomen, followed by the collection of static PET/CT images (skull to mid-thigh) at 45 minutes, 2 and approximately 20 hours postinjection. Time-dependent changes in percentage activity in source organs (kidneys, bladder, salivary glands, small intestine, liver, spleen, and whole body) were determined. Bone marrow and urinary bladder contents residence time were also calculated. Source organs residence time, organ-absorbed doses, and effective doses were determined using OLINDA/EXM software. Physiological tracer uptake was seen in kidneys, liver, spleen, small intestine, urinary bladder, and salivary glands and in metastases. Kidneys with highest radiation absorbed dose of 3.19E-01 mSv/MBq were the critical organs, followed by urinary bladder wall (2.24E-01 mSv/MBq, spleen [1.85E-01], salivary glands [1.11E-01], and liver [1.07E-01] mSv/MBq). Red marrow dose was found to be 3.31E-02 mSv/MBq. The mean effective dose of 3.89E-02 mSv/MBq and effective dose of 1.95 mSv was estimated from 50 MBq (treatment planning dose) of [Sc]Sc-PSMA-617. [Sc]Sc-PSMA-617 is found to be a very promising radiopharmaceutical that can be used for pre [Lu]Lu-PSMA-617 therapeutic dosimetric assessment.

A randomised phase II trial of docetaxel versus docetaxel plus carboplatin in patients with castration-resistant prostate cancer who have progressed after response to prior docetaxel chemotherapy: The RECARDO trial

BackgroundDocetaxel is standard first-line chemotherapy for patients with metastatic castration–resistant prostate carcinoma (mCRPC). Docetaxel re-challenge has never been tested in a prospective randomised controlled study. As some studies support the addition of carboplatin to docetaxel, we performed a phase II trial investigating the combination of docetaxel plus carboplatin versus docetaxel re-treatment in docetaxel pre-treated mCRPC patients. MethodsPatients with mCRPC with a progression-free interval of ≥3 months after initial docetaxel treatment were randomised between docetaxel 75 mg/m2 or docetaxel 60 mg/m2 plus carboplatin AUC4. The primary end-point was progression-free survival (PFS; PSA/RECIST). ResultsOwing to insufficient recruitment, the study was discontinued early after inclusion of 75 patients (targeted 150) PFS and overall survival (OS) were comparable between both groups (median PFS 12.7 months (95% CI 9.9–17.5 months) with docetaxel monotherapy and 11.7 months (95% CI 8.5–21.0 months) with combination therapy (p = 0.98); OS 18.5 months (95% CI 11.8–24.5 months) versus 18.9 months (95% CI 16.0–23.7 months) (p = 0.79). An interim analysis (SEQTEST) showed that the null hypothesis could already be excepted, and no significant difference between both study arms was expected if inclusion would be completed. The incidence of grade 3–4 infections and gastrointestinal side-effects was numerical higher in the carboplatin arm (p = 0.056). ConclusionThis early terminated study suggests no benefit from the addition of carboplatin to docetaxel re-treatment in patients with mCRPC, whereas the combination resulted in more toxicity. Re-treatment with docetaxel monotherapy appears to be feasible, save and effective for patients with mCRPC and an initial good response to docetaxel. Trial registrationNTR3070.

[Strategies for First-Line Treatment of mCRPC].

At present, abiraterone acetate and enzalutamide are the most commonly used substances in the first-line treatment of asymptomatic or mildly symptomatic metastatic castration-resistant prostate carcinoma (mCRPC). Since the relevant pivotal trials have demonstrated comparable clinical efficacy for both substances, further factors should be considered for the choice of treatment. As mCRPC patients usually receive several lines of treatment, different adaptation and resistance mechanisms leading to treatment failure could be important. This is indicated by daily routine observations and some initial clinical studies on resistance and different sequences of therapy. However, until the clinical relevance has been confirmed, it is mostly adverse events and comorbidities that are taken into account for the choice of first-line therapy. Also potential interactions with comedications and patient preferences should be considered. In the first-line treatment of mCRPC, ongoing discussions not only centre around the choice of medication for first-line mCRPC therapy, but also around the point in time they are started. For abiraterone acetate, for example, there is confirmed evidence that patients may benefit from early use within the approved indication. If the clinical importance of the different resistance mechanisms and differences in efficacy of various sequences could be confirmed, this would be a strong argument for therapy decisions and should therefore be further analysed in prospective clinical studies.

A feasibility study to determine T cell responses to neoantigens following treatment with ipilimumab in men with metastatic castration-resistant prostate carcinoma (mCRPC).

e14506Background: Ipilimumab (anti-CTLA-4) promotes durable antitumor responses in a subset of patients with mCRPC. We designed a clinical trial (NCT02113657) to test the hypothesis that the induct...