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.

Prediction of Resistance to 177Lu-PSMA Therapy by Assessment of Baseline Circulating Tumor DNA Biomarkers.

177Lu-PSMA-617 and 177Lu-PSMA I&T (collectively termed 177Lu-PSMA) are currently being used for the treatment of selected metastatic castration-resistant prostate cancer (mCRPC) patients with PSMA PET-positive disease, but biomarkers for these agents remain incompletely understood. Methods: Pretreatment circulating tumor DNA (ctDNA) samples were collected from 44 mCRPC patients receiving 177Lu-PSMA treatment. Prostate-specific antigen responders and nonresponders were assessed relative to the ctDNA findings at baseline. Results: The ctDNA findings indicated that nonresponders were more likely to have gene amplifications than were responders (75% vs. 39.2%, P = 0.03). In particular, amplifications in FGFR1 (25% vs. 0%, P = 0.01) and CCNE1 (31.2% vs. 0%, P = 0.001) were more likely to be present in nonresponders. CDK12 mutations were more likely to be present in nonresponders (25% vs. 3.6%, P = 0.05). Conclusion: Our analyses indicate that ctDNA assays may contain specific biomarkers predictive of response or resistance for 177Lu-PSMA-treated mCRPC patients. Additional confirmatory studies are required before clinicians can use these findings to make personalized treatment decisions.

Treatment outcomes of radium-223 in patients with metastatic castration-resistant prostate cancer: An experience before National Health Insurance reimbursement in Taiwan.

BACKGROUND: Radium-223 (Ra-223), an α-particle-emitting isotope, inhibits bony metastases and prevents patients from skeletal-related events in metastatic castration-resistant prostate cancer (mCRPC). We retrospectively reviewed the treatment response, predictive factors, and adverse events (AEs) of Ra-223 before the National Health Insurance reimbursement in a Taiwanese tertiary institute. METHODS: Patients treated with Ra-223 before January 2019 were enrolled and categorized into progressive disease (PD) and clinical benefits (CB) groups. Laboratory data before and after the treatment were collected, and spider plots concerning percentage changes of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and prostate-specific antigen (PSA) were prepared and calculated statistically. CB/PD, baseline ALP, LDH, and PSA levels were also adopted as stratification factors for overall survival (OS). RESULTS: Among 19 patients included, 5 (26.3%) and 14 (73.4%) belonged to the PD and CB groups, respectively, with no significant difference observed in the baseline laboratory data. The percentage changes in ALP, LDH, and PSA levels after Ra-223 treatment were statistically significant among the two groups (ALP: CB 54.3 ± 21.4% vs PD 77.6 ± 11.8%, p = 0.044; LDH: CB 88.2 ± 22.8% vs PD 138.3 ± 49.0%, p = 0.046; PSA: CB 97.8 ± 61.7% vs PD 277.0 ± 101.1%, p = 0.002). The trends of LDH between the two groups in spider plot were separated significantly. There were no differences in the AEs between the two groups. CB had a longer median OS than the PD group (20.50 months vs 9.43 months, p = 0.009). Patients with LDH <250 U/L at baseline tended to have longer OS but without significance. CONCLUSION: The CB rate of Ra-223 was 73.7%. No predictive factor for treatment response was obtained from pretreatment data. The mean percentage changes in ALP, LDH, and PSA levels compared with baseline significantly differed between the CB and PD groups, especially the LDH levels. The CB and PD groups showed different OS, with LDH levels exhibiting the potential to predict OS.

Cost-Effectiveness Analysis of 177Lu-PSMA-617 Radioligand Therapy in Metastatic Castration-Resistant Prostate Cancer.

BACKGROUND: Metastatic castration-resistant prostate cancer poses a therapeutic challenge with poor prognosis. The VISION trial showed prolonged progression-free and overall survival in patients treated with lutetium Lu 177 vipivotide tetraxetan (177Lu-PSMA-617) radioligand therapy compared with using the standard of care (SoC) alone. The objective of this study was to determine the cost-effectiveness of 177Lu-PSMA-617 treatment compared with SoC therapy. METHODS: A partitioned survival model was developed using data from the VISION trial, which included overall and progression-free survival and treatment regimens for 177Lu-PSMA-617 and SoC. Treatment costs, utilities for health states, and adverse events were derived from public databases and the literature. Because 177Lu-PSMA-617 was only recently approved, costs for treatment were extrapolated from 177Lu-DOTATATE. Outcome measurements included the incremental cost, effectiveness, and cost-effectiveness ratio. The analysis was performed in a US setting from a healthcare system perspective over the lifetime horizon of 60 months. The willingness-to-pay threshold was set to $50,000, $100,000, and $200,000 per quality-adjusted life years (QALYs). RESULTS: The 177Lu-PSMA-617 group was estimated to gain 0.42 incremental QALYs. Treatment using 177Lu-PSMA-617 led to an increase in costs compared with SoC ($169,110 vs $85,398). The incremental cost, effectiveness, and cost-effectiveness ratio for 177Lu-PSMA-617 therapy was $200,708/QALYs. Sensitivity analysis showed robustness of the model regarding various parameters, which remained cost-effective at all lower and upper parameter bounds. In probabilistic sensitivity analysis using Monte Carlo simulation with 10,000 iterations, therapy using 177Lu-PSMA-617 was determined as the cost-effective strategy in 37.14% of all iterations at a willingness-to-pay threshold of $200,000/QALYs. CONCLUSIONS: Treatment using 177Lu-PSMA-617 was estimated to add a notable clinical benefit over SoC alone. Based on the model results, radioligand therapy represents a treatment strategy for patients with metastatic castration-resistant prostate cancer with cost-effectiveness in certain scenarios.

Prognostic Value of Tumor Volume Assessment on PSMA PET After 177Lu-PSMA Radioligand Therapy Evaluated by PSMA PET/CT Consensus Statement and RECIP 1.0.

Quantitative evaluation of prostate-specific membrane antigen (PSMA)-targeting PET/CT remains challenging but is urgently needed for the use of standardized PET-based response criteria, such as the PSMA PET/CT consensus statement or Response Evaluation Criteria in PSMA PET/CT (RECIP 1.0). A recent study evaluated the prognostic value of whole-body tumor volume using a semiautomatic method relying on a 50% threshold of lesion SUVmax (PSMATV50). In the present study, we analyzed the suitability of this approach comparing 18F-PSMA-1007 with 68Ga-PSMA-11 PET/CT scans and the potential of PSMATV50 for the prediction of overall survival (OS) in patients before 177Lu-PSMA radioligand therapy (RLT). Moreover, PSMATV50 was integrated into the PSMA PET/CT consensus statement as well as RECIP 1.0, and the prognostic value of these response classification systems was compared. Methods: This retrospective study included 70 patients with metastatic castration-resistant prostate cancer undergoing PSMA RLT. Thirty-three patients were monitored by 68Ga-PSMA-11 PET/CT, and 37 patients by 18F-PSMA-1007 PET/CT. PET/CT scans before (baseline) and at the end of PSMA RLT after 2-4 cycles (follow-up) were separately analyzed by 2 readers. PSMATV50 at baseline and its change at the time of follow-up (ΔPSMATV50, expressed as a ratio) were correlated with OS using Cox proportional-hazards regression. The results of both subgroups were compared. The integration of ΔPSMATV50 in existing response classification systems was evaluated. To assess and compare the discriminatory strength of these classification systems, Gönen and Heller concordance probability estimates were calculated. Results: PSMATV50 determination was technically feasible in all examinations. A higher PSMATV50 at baseline and a higher ΔPSMATV50 were strongly associated with a shorter OS for both 68Ga-PSMA-11 (PSMATV50: hazard ratio [HR] of 1.29 [95% CI, 1.05-1.55], P = 0.009; ΔPSMATV50: HR of 1.83 [95% CI, 1.08-3.09], P = 0.024) and 18F-PSMA-1007 (PSMATV50: HR of 1.84 [95% CI, 1.13-2.99], P = 0.014; ΔPSMATV50: HR of 1.23 [95% CI, 1.04-1.51], P = 0.03). Response assessment provided high discriminatory power for OS for the PSMA PET/CT consensus statement (concordance probability estimate, 0.73) as well as RECIP 1.0 (concordance probability estimate, 0.74). Conclusion: PSMATV50 and ΔPSMATV50 proved to be predictive of OS not only for 68Ga-PSMA-11 but also for 18F-PSMA-1007 PET/CT scans. Subsequent integration of ΔPSMATV50 into the PSMA PET/CT consensus statement and RECIP 1.0 provided equally high prognostic value for both classification systems.

Early molecular imaging response assessment based on determination of total viable tumor burden in [68Ga]Ga-PSMA-11 PET/CT independently predicts overall survival in [177Lu]Lu-PSMA-617 radioligand therapy.

PURPOSE: In patients with metastatic castration-resistant prostate cancer (mCRPC) treated with prostate-specific membrane antigen-targeted radioligand therapy (PSMA-RLT), the predictive value of PSMA PET/CT-derived response is still under investigation. Early molecular imaging response based on total viable tumor burden and its association with overall survival (OS) was explored in this study. METHODS: Sixty-six mCRPC patients who received [177Lu]Lu-PSMA-617 RLT within a prospective patient registry (REALITY Study, NCT04833517) were analyzed. Patients received a [68Ga]Ga-PSMA-11 PET/CT scan before the first and after the second cycle of PSMA-RLT. Total lesion PSMA (TLP) was determined by semiautomatic whole-body tumor segmentation. Molecular imaging response was assessed by change in TLP and modified PERCIST criteria. Biochemical response was assessed using standard serum PSA and PCWG3 criteria. Both response assessment methods and additional baseline parameters were analyzed regarding their association with OS by univariate and multivariable analysis. RESULTS: By molecular imaging, 40/66 (60.6%) patients showed partial remission (PR), 19/66 (28.7%) stable disease (SD), and 7/66 (10.6%) progressive disease (PD). Biochemical response assessment revealed PR in 34/66 (51.5%) patients, SD in 20/66 (30.3%), and PD in 12/66 (18.2%). Response assessments were concordant in 49/66 (74.3%) cases. On univariate analysis, both molecular and biochemical response (p = 0.001 and 0.008, respectively) as well as two baseline characteristics (ALP and ECOG) were each significantly associated with OS. The median OS of patients showing molecular PR was 24.6 versus 10.7 months in the remaining patients (with SD or PD). On multivariable analysis molecular imaging response remained an independent predictor of OS (p = 0.002), eliminating biochemical response as insignificant (p = 0.515). CONCLUSION: The new whole-body molecular imaging-derived biomarker, early change of total lesion PSMA (TLP), independently predicts overall survival in [177Lu]Lu-PSMA-617 RLT in mCRPC, outperforming conventional PSA-based response assessment. TLP might be considered a more distinguished and advanced biomarker for monitoring PSMA-RLT over commonly used serum PSA.

A qualitative research study in Japan investigating patients' experience with metastatic castration-resistant prostate cancer: from diagnosis to decision for Ra-223 treatment.

Aim: This qualitative study aimed to reveal symptoms and impacts among bone metastatic castration-resistant prostate cancer (or mCRPC) Japanese patients, prior to Radium-223 (Ra-223) treatment. Materials & Methods: Twenty-three mCRPC patients designated to receive Ra-223 and three treating physicians (Ra-223 prescribers) in Japan, were interviewed. All interview data were assessed for concept frequency, themes and saturation. Results: Forty-five percent of the patients (mean age: 75.8 years) were symptomatic at the time of enrollment. Interviews with all patients revealed 47 mCRPC symptoms, including back pain and bone-specific pain, and 45 life impacts, including worry about disease progression and the impact on daily, physical activities. Conclusion: The symptoms and impacts of living with mCRPC and the associated burden of bone metastasis and skeletal-related symptoms are varied and are important considerations for treatment.

Lay abstract Aim: This study looked at symptoms and impacts among patients with a type of prostate cancer called metastatic castration-resistant prostate cancer. This cancer has spread to other parts of the body including patients' bones. Patients' prostate-specific antigen levels continue to rise despite surgical or medical treatment and their doctors decided the next best treatment is Radium-223 (Ra-223), a radiopharmaceutical therapy. Materials & methods: Twenty-three metastatic castration-resistant prostate cancer patients designated to receive Ra-223 and three treating physicians (Ra-223 prescribers) in Japan, were interviewed. All interview data were assessed for the number of times some words or themes are mentioned by the patients. Results: Ten of the 23 patients (average age of 76 years) had symptoms when the study started. Interviewed patients talked about symptoms including back pain and pain in their bones, and how their cancer caused them to worry about their physical activities and disease progression. Conclusion: The symptoms impact on patients' daily living and the burden of bone metastasis and bone-related symptoms are varied and are important considerations for treatment.

Response Assessment and Prediction of Progression-Free Survival by 68Ga-PSMA-11 PET/CT Based on Tumor-to-Liver Ratio (TLR) in Patients with mCRPC Undergoing 177Lu-PSMA-617 Radioligand Therapy.

At present, little is known about the molecular imaging-based response assessment of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy with 177Lutetium (177Lu-PSMA-617 RLT) in metastatic castration-resistant prostate cancer (mCRPC). Our study evaluated the response to RLT using both molecular imaging and biochemical response assessments, and their potential prediction of progression-free survival (PFS). Fifty-one consecutive patients given two cycles of RLT at 6-week intervals were analyzed retrospectively. 68Ga-PSMA-11 PET/CT was obtained about 2 weeks prior to the first and 4-6 weeks after the second cycle. Molecular imaging-based response using SUVpeak and tumor-to-liver ratio (TLR) was determined by modified PERCIST criteria. ∆TLR and ∆SUV were significantly correlated with ∆PSA (p < 0.001, each). After a median follow-up of 49 months, the median PFS (95% CI) was 8.0 (5.9-10.1) months. In univariate analysis, responders showing partial remission (PRPSA and PRTLR) had significantly (p < 0.001, each) longer PFS (median: 10.5 and 9.3 months) than non-responders showing either stable or progressive disease (median: 4.0 and 3.5 months). Response assessment using SUVpeak failed to predict survival. In multivariable analysis, response assessment using TLR was independently associated with PFS (p < 0.001), as was good performance status (p = 0.002). Molecular imaging-based response assessment with 68Ga-PSMA-11 PET/CT using normalization of the total lesion PSMA over healthy liver tissue uptake (TLR) could be an appropriate biomarker to monitor RLT in mCRPC patients and to predict progression-free survival (PFS) of this treatment modality.

Microdosimetry-based determination of tumour control probability curves for treatments with 225Ac-PSMA of metastatic castration resistant prostate cancer.

We performed Monte Carlo simulations in order to determine, by means of microdosimetry calculations, tumour control probability (TCP) curves for treatments with 225Ac-PSMA of metastatic castration resistant prostate cancer (mCRPC). Realistic values of cell radiosensitivity, nucleus size and lesion size were used for calculations. As the cell radiosensitivity decreased, the nucleus size decreased and the lesion size increased, the absorbed dose to reach a given TCP increased. The widest variations occurred with regard to the cell radiosensitivity. For the Monte Carlo simulations, in order to address a non-uniform PSMA expression, different 225Ac-PSMA distributions were considered. The effect of these different PSMA distributions resulted in small variations in the TCP curves (maximum variation of 5%). Absorbed doses to reach a TCP of 0.9 for a uniform 225Ac-PSMA distribution, considering a relative biological effectiveness (RBE) of 5, ranged between 35.0 Gy and 116.5 Gy. The lesion absorbed doses per administered activity reported in a study on treatments with 225Ac-PSMA of mCRPC ranged between 1.3 Gy MBq-1 and 9.8 Gy MBq-1 for a RBE = 5. For a 70 kg-patient to whom 100 kBq kg-1 of 225Ac-PSMA are administered, the range of lesion absorbed doses would be between 9.1 Gy and 68.6 Gy. Thus, for a single cycle of 100 kBq kg-1, a number of lesions would not receive an absorbed dose high enough to reach a TCP of 0.9.

Estimation of [177Lu]PSMA-617 tumor uptake based on voxel-wise 3D Monte Carlo tumor dosimetry in patients with metastasized castration resistant prostate cancer.

OBJECTIVE: Patients with advanced prostate cancer are suitable candidates for [177Lu]PSMA-617 therapy. Integrated SPECT/CT systems have the potential to improve the accuracy of patient-specific tumor dosimetry. We present a novel patient-specific Monte Carlo based voxel-wise dosimetry approach to determine organ and total tumor doses (TTD). METHODS: 13 patients with histologically confirmed metastasized castration-resistant prostate cancer were treated with a total of 18 cycles of [177Lu]PSMA-617 therapy. In each patient, dosimetry was performed after the first cycle of [177Lu]PSMA-617 therapy. Regions of interest were defined manually on the SPECT/CT images for the kidneys, spleen and all 295 PSMA-positive tumor lesions in the field of view. The absorbed dose to normal organs and to all tumor lesions were calculated by a three dimensional dosimetry method based on Monte Carlo Simulations. RESULTS: The average dose values yielded the following results: 2.59 ±â€Š0.63 Gy (1.67-3.92 Gy) for the kidneys, 0.79 ± 0.46 Gy (0.31-1.90 Gy) for the spleen and 11.00 ±â€Š11.97 Gy (1.28-49.10 Gy) for all tracer-positive tumor lesions. A trend towards higher TTD was observed in patients with Gleason Scores > 8 compared to Gleason Scores ≤ 8 and in lymph node metastases compared to bone metastases. A significant correlation was determined between the serum-PSA level before RLT and the TTD (r = -0.57, p < 0.05), as well as between the TTD with the percentage change of serum-PSA levels before and after therapy was observed (r = -0.57, p < 0.05). Patients with higher total tumor volumes of PSMA-positive lesions demonstrated significantly lower kidney average dose values (r = -0.58, p < 0.05). CONCLUSION: The presented novel Monte Carlo based voxel-wise dosimetry calculates a patient specific whole-body dose distribution, thus taking into account individual anatomies and tissue compositions showing promising results for the estimation of radiation doses of normal organs and PSMA-positive tumor lesions.

Response assessment using [68 Ga]Ga-PSMA ligand PET in patients undergoing systemic therapy for metastatic castration-resistant prostate cancer.

BACKGROUND: To assess which parameters of [68 Ga]Ga-PSMA-11 positron emission tomography (PSMA-PET) predict response to systemic therapies in metastatic (m) castration-resistant prostate cancer (CRPC). In addition, to investigate which of these factors are associated with overall survival (OS). METHODS: We retrospectively assessed the following PSMA-PET parameters in 43 patients before and after systemic therapies for mCRPC: PSMA total tumor volume (TTV), mean standardized uptake value (SUVmean), SUVmax, and SUVpeak. prostate-specific antigen (PSA) levels and PSMA-PET/CT(magnetic resonance imaging [MRI]) imaging were both performed within 8 weeks before and 6 weeks after systemic therapy. PSMA-PET and CT (MRI) images were reviewed according to the modified PET Response Criteria in Solid Tumors (PERCIST) and Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Results were compared to PSA response. Univariable survival analyses were performed. RESULTS: Overall, 43 patients undergoing 67 systemic therapies were included (9 patients radium-223, 12 cabazitaxel, 22 docetaxel, 6 abiraterone, and 18 enzalutamide). Median serum PSA level before any therapy was 11.3 ng/mL (interquartile range [IQR] = 3.3, 30.1). Delta (d) PSA after systemic therapies was -41%, dTTV 10.5%, dSUVmean -7.5%, dSUVmax -13.3%, dSUVpeak -12%, and dRECIST -13.3%. Overall, 31 patients had dPSA response (46.3%), 12 stable disease (17.9%), and 24 progressive disease (35.8%). All observed PET parameters, as well as the RECIST evaluation, were significantly associated with PSA response (dTTV P = .003, dSUVmean P = .003, dSUVmax P = .011, dSUVpeak P < 0001, dRECIST P = .012), while RECIST assessment was applicable in 37 out of 67 patients (55.2%). Within a median follow-up of 33 months (IQR = 26, 38), 10 patients (23.3%) died of PC. On univariable survival analyses, neither the investigated PET parameters nor PSA level or RECIST criteria were associated with OS. CONCLUSION: PSMA-PET provides reliable parameters for prediction of response to systemic therapies for mCRPC. These parameters, if confirmed, could enhance RECIST criteria, specifically concerning its limitations for sclerotic bone lesions.

Determination of whole-body tumour burden on [68Ga]PSMA-11 PET/CT for response assessment of [177Lu]PSMA-617 radioligand therapy: a retrospective analysis of serum PSA level and imaging derived parameters before and after two cycles of therapy.

AIM: In patients with metastasized castration-resistant prostate cancer a reliable imaging-based therapy response assessment in addition to PSA kinetics is desirable. Recently, measurements of whole-body tumour burden by [68Ga]PSMA-11 PET/CT have been reported for response assessment in oligometastasic patients. The present study investigated the association of PSMA PET derived parameters and serum PSA level before and after [177Lu]PSMA-617 radioligand therapy (RLT). METHODS: This retrospective study assessed whole-body PSMA tumour volume (PSMA-TV) in 10 patients with multifocal to diffuse metastases before and after 2 cycles of RLT using volume of interest (VOI) analysis. A standardized uptake value (SUV) threshold-based approach was used to semi-automatically delineate all voxels with a SUV ≥ 2.0 g/ml using the software ROVER® (ABX Radeberg, Germany). Voxels with physiological tracer uptake (e. g. kidneys) were excluded manually. Correlations between PSMA-TV and serum PSA level before and after two cycles of RLT as well as changes thereof (ΔPSMA-TV and ΔPSA, respectively) were calculated. RESULTS: Changes of ΔPSMA-TV and ΔPSA were concordant in 7 of 10 patients. Whereas a good correlation was found between PSMA-TV and PSA before RLT (ρ = 0.81, p = 0.0049), this correlation was attenuated after RLT (ρ = 0.64, p = 0.0479). Consequently, no association was found between ΔPSMA-TV and ΔPSA (ρ = 0.39, p = 0.26). CONCLUSION: The attenuation of the correlation of PSA and PSMA-TV after RLT suggests that in patients with advanced disease the comparison of imaging based parameters such as PSMA-TV and PSA level might be useful for an adequate monitoring of treatment response.

Response assessment using 68Ga-PSMA ligand PET in patients undergoing 177Lu-PSMA radioligand therapy for metastatic castration-resistant prostate cancer.

PURPOSE: The first aim of this study was to evaluate 68Ga-PSMAHBED-CC conjugate 11 positron emission tomography (PSMA PET) parameters for assessment of response to 177Lu-PSMA-617 radioligand therapy (RLT) in patients with metastatic castration-resistant prostate cancer (mCRPC). The second aim was to investigate factors associated with overall survival (OS). METHODS: We retrospectively assessed mean standardized uptake values (SUVmean) and total tumor volumes (TTV) on PSMA PET in 38 of 55 mCRPC patients before and after RLT. PSA testing and PSMA PET/CT(MRI) imaging were performed during the 8 weeks before and the 6 weeks after RLT. PSMA PET and CT(MRI) images were reviewed separately according to the modified PET Response Criteria in Solid Tumors (mPERCIST) and RECIST1.1. The results were compared with PSA responses. Associations between OS and the RECIST evaluation and changes in SUVmean, TTV, and PSA, CRP, LDH, hemoglobin and ALP levels were determined in a univariable survival analysis. RESULTS: The median PSA level at the time of pretherapy PSMA PET/CT(MRI) was 60.8 ng/ml (IQR 15.4, 264.2 ng/ml). After RLT the median PSA level decreased by 44%, TTV by 45.1%, SUVmean by 25.8% and RECIST by 11.3%. A PSA response was seen in 18 patients (47.4%), stable disease in 12 (31.6%) and progressive disease in 8 (21.1%). Contrary to the changes in SUVmean and the RECIST evaluation, the change in TTV was significantly associated with PSA response (p = 0.15, p = 0.58, and p < 0.001, respectively). After a median follow-up of 17 months (IQR 8.0, 24.2 months), 11 patients (28.9%) had died of their prostate cancer. The changes in both TTV and PSA levels were associated with OS (HR 1.001, 95% CI 1-1.003, p = 0.04, and HR 1.004, 95% CI 1.001-1.008, p = 0.01, respectively), while the changes in SUVmean and the RECIST evaluation were not. The pre-therapy CRP level was also associated with OS (HR 1.07, 95% CI 1.009-1.14, p = 0.02). CONCLUSION: TTV on PSMA PET seems to be a reliable parameter for response assessment in mCRPC patients undergoing RLT and might overcome the limitations of RECIST in prostate cancer. Furthermore, the change in TTV was significantly associated with OS in our cohort.

Comparison of microdosimetry-based absorbed doses to control tumours and clinically obtained tumour absorbed doses in treatments with 223Ra.

We performed Monte Carlo simulations in order to determine by means of microdosimetry calculations the average number of hits to the cell nucleus required to reach a tumour control probability (TCP) of 0.9, [Formula: see text], for the source geometry of a nucleus embedded in a homogeneous distribution of 223Ra atoms. From the results obtained and following the MIRD methodology, we determined the values of lesion absorbed doses needed to reach a TCP of 0.9, [Formula: see text], for different values of mass density, cell radiosensitivity, nucleus radius and lesion volume. The greatest variation of those absorbed doses occurred with cell radiosensitivity and no dependence was found on mass density. The source geometry used was chosen because we aimed to compare the values of [Formula: see text] with the lesion absorbed doses obtained from image-based macrodosimetry in treatments of metastatic castration-resistant prostate cancer with 223Ra which were obtained assuming a homogeneous distribution of 223Ra atoms within the lesion. In a comparison with a study including 29 lesions, results showed that even for the case of the most radiosensitive cells simulated, 45% of the lesions treated following a schedule of two cycles of 110 kBq kg-1 body mass would receive absorbed doses below the values of [Formula: see text] determined in this study.

[Lutetium-177-PSMA radioligand therapy : Consensus within the framework of GKV-funded care between the university hospitals in Aachen, Bonn, Düsseldorf, Essen, and Cologne and the MDK Nordrhein]. / Lutetium-177-PSMA-Radioligandentherapie : Konsensus im Rahmen der GKV-finanzierten Versorgung zwischen den Hochschulkliniken in Aachen, Bonn, Düsseldorf, Essen und Köln und dem MDK Nordrhein.

In the last 3 years, Lutetium-177 prostate-specific membrane antigen radioligand therapy (Lu-177-PSMA-RLT) has received increasing attention in nuclear medicine as a new form of treatment for castration-resistant metastatic prostate cancer. This therapy combines the radionuclide Lutetium-177, which has been therapeutically used in nuclear medicine for many years, with a molecular target of the transmembrane prostate-specific membrane antigen expressed by prostate cancer cells. Since there are no prospective randomized studies on Lu-177-PSMA-RLT and the question of reimbursement has repeatedly been the subject of review by the MDK Nordrhein (Medischenische Dienst der Krankenversicherung), there was a desire because of the increasing number of patients being treated to clarify under which circumstances Lu-177-PSMA-RLT can be reimbursed by German statutory health insurance. The goals of this article are to help treating physicians understand how this new therapy option works, to integrate it in the overall therapy concept for castration-resistant metastatic prostate cancer, and, above all, to use Lu-177-PSMA-RLT-based on the current data-at the right place in the therapy sequence of castration-resistant metastatic prostate cancer.

223Ra Therapy of Advanced Metastatic Castration-Resistant Prostate Cancer: Quantitative Assessment of Skeletal Tumor Burden for Prognostication of Clinical Outcome and Hematologic Toxicity.

The aim of this study was to investigate the prognostic value of the quantitative assessment of skeletal tumor burden on bone scintigraphy (Bone Scan Index [BSI]) in patients who have advanced metastatic castration-resistant prostate cancer (mCRPC) and are receiving 223RaCl2 We hypothesized that the BSI can serve as a prognostic biomarker of overall survival (OS) and hematologic toxicity and as a tool for response assessment in patients with mCRPC treated with 223RaCl2Methods: This study was a retrospective investigation of a Danish cohort of mCRPC patients who received 223RaCl2 therapy between March 2014 and October 2015 and for whom baseline bone scintigraphy was available. Bone scintigraphy studies were reviewed and graded according to the extent of disease. Furthermore, an automated BSI (EXINI BoneBSI) was obtained for baseline scintigraphy studies and follow-up scans after 3 cycles as well as at the end of therapy. Clinical outcomes were OS and occurrence of hematologic toxicity of grades 2-5. Associations between the BSI and clinical outcomes were investigated in multivariate regression models including the visual assessment of bone scintigraphy and other relevant covariates. Results: A total of 88 patients were included. The median number of completed 223RaCl2 cycles was 4, and 27 patients (31%) completed 6 cycles. The BSI was significantly associated with OS in the multivariate analysis; the median OS for patients with a BSI of greater than 5 was 8.2 mo, and the median OS for patients with a BSI of less than or equal to 5 was 15.0 mo (hazard ratio, 2.65 [95% confidence interval, 1.5-4.71]; P = 0.001). Likewise, the baseline BSI was prognostic for the occurrence of hematologic toxicity; patients with a BSI of greater than 5 had an odds ratio of 3.02 (95% confidence interval, 1.2-7.8; P = 0.02) for toxicity. The BSI declined during therapy in 44% of the patients who completed 3 cycles of 223RaCl2 (n = 52) and in 84% of the patients after the end of therapy (n = 32). There was no significant association between a change in the BSI during therapy and OS. Conclusion: The BSI is a promising biomarker for prognostication of OS and hematologic toxicity in late-stage mCRPC patients receiving 223RaCl2 Further prospective studies are needed to evaluate the potential of the BSI for response assessment in 223RaCl2 therapy.

Response Assessment of 223Ra Treatment: Should a Fluorocholine PET/CT Be Performed?

We present 3 cases of patients with castration-resistant prostate cancer and bone metastases treated with Ra, belonging to our prospective and multicenter ChoPET-Rad study. All patients underwent clinical, hematological, and biochemical monitoring between each Ra administration. Initial and follow-up F-fluorocholine PET/CT and Tc-biphosphonate bone scintigraphy were performed previously and after the third Ra administration. Both techniques correctly established the response to treatment, in agreement to the biochemical response, although differences in the disease expression (concordant and discordant patterns) were found because of the different radiotracer biodistribution and molecular information derived from them.

177Lu-DKFZ-PSMA-617 therapy in metastatic castration resistant prostate cancer: safety, efficacy, and quality of life assessment.

PURPOSE: The purpose of this study was to evaluate the efficacy and safety of a novel theranostic agent, 177Lu-DKFZ-PSMA-617 therapy in metastatic castration resistant prostate cancer (mCRPC). METHODS: Thirty-one mCRPC patients with progressive disease despite second-line hormonal therapy and/or docetaxel chemotherapy were recruited for the study. All patients underwent diagnostic68Ga-PSMA-HBED-CCPET/CT, prior to inclusion for therapy. Included patients then underwent quarterly 177Lu-DKFZ-PSMA-617 therapy. Hematological, kidney function, liver function tests, and serum PSA levels were recorded before and after therapy at 2 weeks, 4 weeks, and 3 month intervals. Biochemical response was assessed with trend in serum PSA levels. Metabolic response was assessed by PERCIST 1 criteria. Clinical response was assessed by visual analogue score (VASmax) analgesic score (AS), Karanofsky performance status (KPS), and ttoxicity and response criteria of the Eastern Cooperative Oncology Group (ECOG) criteria. RESULTS: The mean age of patients was 65.93 ± 9.77 years (range: 38-81 years). The mean activity administered in the 31 patients was 5069 ± 1845 MBq ranging from one to four cycles. There was a decline in the mean serum PSA levels from the baseline (baseline: 275 ng/mL, post 1st cycle therapy: 141.75 ng/mL). Based on biochemical response criteria 2/31, 20/31, 3/31, and 6/31 had complete response (CR), partial response(PR), stable disease (SD), and progressive disease (PD), respectively. Metabolic response revealed 2/6 patients with CR, and the remaining 3/6 patients with PR and 1/6 patients with SD. The mean VASmax score decreased from 7.5 to 3. The mean analgesic score decreased from 2.5 to 1.8 after therapy. The mean KPS score improved from 50.32 to 65.42 after therapies. The mean ECOG performance status improved from 2.54 to 1.78 after therapy. Two patients experienced grade I and grade II hemoglobin toxicity each. None of the patients experienced nephrotoxicity or hepatotoxicity. CONCLUSION: 177Lu-DKFZ-PSMA-617 radionuclide therapy is a safe and effective approach in the treatment of mCRPC patients.

Radium-223: Insight and Perspectives in Bone-metastatic Castration-resistant Prostate Cancer.

223Ra prolongs overall survival in symptomatic patients affected by multiple bone-metastatic castration-resistant prostatic cancer, without visceral or nodal involvement. However, many questions remain about its mechanisms of action, and its use in clinical practice is still unresolved. First of all, what is the main target of alpha-particle emission, that is, in what way does it influences the tumor microenvironment? When is the best timing in the course of the disease, extending its use to asymptomatic low-volume or even to the micrometastatic phase? What are suitable biomarkers to be employed as prognostic factors and response indicators? Which associations with other drugs and their sequence can offer the best results, and is their effect additive or synergistic? Ultimately, in the current climate of spending review, what is the optimal cost and benefit ratio regarding available treatments? In this review, we tried to answer these questions by analyzing the available scientific literature.