Actinium-225-PSMA radioligand therapy of metastatic castration-resistant prostate cancer (WARMTH Act): a multicentre, retrospective study

BACKGROUND

Actinium-225 (225Ac) prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) is a novel therapy for metastatic castration-resistant prostate cancer (mCRPC). We aimed to report the safety and antitumour activity of 225Ac-PSMA RLT of mCRPC in a large cohort of patients treated at multiple centres across the world.

METHODS

This retrospective study included patients treated at seven centres in Australia, India, Germany, and South Africa. We pooled data of consecutive patients of any age and Eastern Cooperative Oncology Group performance status with histopathologically confirmed adenocarcinoma of the prostate who were treated with one or more cycles of 8 MBq 225Ac-PSMA RLT administered intravenously for mCRPC. Previous lines of mCRPC treatment included taxane-based chemotherapy, androgen-receptor-axis inhibitors, lutetium-177 (177Lu) PSMA RLT, and radium-223 dichloride. The primary outcomes were overall survival and progression-free survival.

FINDINGS

Between Jan 1, 2016, and May 31, 2023, 488 men with mCRPC received 1174 cycles of 225Ac-PSMA RLT (median two cycles, IQR 2-4). The mean age of the patients was 68·1 years (SD 8·8), and the median baseline prostate-specific antigen was 169·5 ng/mL (IQR 34·6-519·8). Previous lines of treatment were docetaxel in 324 (66%) patients, cabazitaxel in 103 (21%) patients, abiraterone in 191 (39%) patients, enzalutamide in 188 (39%) patients, 177Lu-PSMA RLT in 154 (32%) patients, and radium-223 dichloride in 18 (4%) patients. The median follow-up duration was 9·0 months (IQR 5·0-17·5). The median overall survival was 15·5 months (95% CI 13·4-18·3) and median progression-free survival was 7·9 months (6·8-8·9). In 347 (71%) of 488 patients, information regarding treatment-induced xerostomia was available, and 236 (68%) of the 347 patients reported xerostomia after the first cycle of 225Ac-PSMA RLT. All patients who received more than seven cycles of 225Ac-PSMA RLT reported xerostomia. Grade 3 or higher anaemia occurred in 64 (13%) of 488 patients, leukopenia in 19 (4%), thrombocytopenia in 32 (7%), and renal toxicity in 22 (5%). No serious adverse events or treatment-related deaths were recorded.

INTERPRETATION

225Ac-PSMA RLT shows a substantial antitumour effect in mCRPC and represents a viable therapy option in patients treated with previous lines of approved agents. Xerostomia is a common side-effect. Severe bone marrow and renal toxicity are less common adverse events.

FUNDING

None.

Long-Term Nephrotoxicity of 177Lu-PSMA Radioligand Therapy

β-emitting 177Lu targeting prostate-specific membrane antigen (PSMA) is an approved treatment option for metastatic castration-resistant prostate cancer. Data on its long-term nephrotoxicity are sparse. This study aimed to retrospectively evaluate post-177Lu-PSMA estimated glomerular filtration rate (eGFR) dynamics for at least 12 mo in a cohort of metastatic castration-resistant prostate cancer patients. Methods: The institutional databases of 3 German tertiary referral centers identified 106 patients who underwent at least 4 cycles of 177Lu-PSMA and had at least 12 mo of eGFR follow-up data. eGFR (by the Chronic Kidney Disease Epidemiology Collaboration formula) at 3, 6, and 12 mo after 177Lu-PSMA radioligand therapy was estimated using monoexponentially fitted curves through available eGFR data. eGFR changes were grouped (≥15%-<30%, moderate; ≥30%-<40%, severe; and ≥40%, very severe). Associations between eGFR changes (%) and nephrotoxic risk factors, prior treatment lines, and number of 177Lu-PSMA cycles were analyzed using multivariable linear regression. Results: At least moderate eGFR decreases were present in 45% (48/106) of patients; of those, nearly half (23/48) had a severe or very severe eGFR decrease. A higher number of risk factors at baseline (-4.51, P = 0.03) was associated with a greater eGFR decrease. Limitations of the study were the retrospective design, lack of a control group, and limited number of patients with a follow-up longer than 1 y. Conclusion: A considerable proportion of patients may experience moderate or severe decreases in eGFR 1 y from initiation of 177Lu-PSMA. A higher number of risk factors at baseline seems to aggravate loss of renal function. Further prospective trials are warranted to estimate the nephrotoxic potential of 177Lu-PSMA.

Comparative Analysis of Morphological and Functional Effects of 225Ac- and 177Lu-PSMA Radioligand Therapies (RLTs) on Salivary Glands

Most Prostate Specific Membrane Antigens (PSMAs) targeting small molecules accumulate in the salivary glands (SGs), raising concerns about SG toxicity, especially after repeated therapies or therapy with 225Ac-labeled ligands. SG toxicity is assessed clinically by the severity of patient-reported xerostomia, but this parameter can be challenging to objectively quantify. Therefore, we explored the feasibility of using SG volume as a biomarker for toxicity. In 21 patients with late-stage metastatic resistant prostate cancer (mCRPC), the PSMA volume and ligand uptake of SG were analyzed retrospectively before and after two cycles of 177Lu-PSMA (LuPSMA; cohort A) and before and after one cycle of 225Ac-PSMA-617 (AcPSMA, cohort B). Mean Volume-SG in cohort A was 59 ± 13 vs. 54 ± 16 mL (-10%, p = 0.4), and in cohort B, it was 50 ± 13 vs. 40 ± 11 mL (-20%, p = 0.007), respectively. A statistically significant decrease in the activity concentration in the SG was only observed in group B (SUVmean: 9.2 ± 2.8 vs. 5.3 ± 1.8, p < 0.0001; vs. A: SUVmean: 11.2 ± 3.3 vs. 11.1 ± 3.5, p = 0.8). SG volume and PSMA-ligand uptake are promising markers to monitor the SG toxicity after a PSMA RLT.

Improved Quality of Life in Metastatic Castration-Resistant Prostate Cancer Patients Receiving Consecutive Cycles of 177Lu-PSMA I&T

The aim of this retrospective analysis was to evaluate health-related quality of life (HRQoL) for patients with metastatic castration-resistant prostate cancer (mCRPC) receiving consecutive cycles of 177Lu-prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) using the reliable and validated European Organisation for Research and Treatment of Cancer core quality-of-life (QoL) questionnaire. In addition, differences in HRQoL between patients with early discontinuation of treatment because of disease progression and patients who were defined as eligible for treatment continuation were analyzed. Methods: In total, 60 mCRPC patients were included in this analysis. The European Organisation for Research and Treatment of Cancer core QoL questionnaire was completed at baseline, before each treatment cycle up to the sixth treatment cycle, and at the time of PSMA-ligand PET/CT scans after the second and fourth treatment cycles. QoL assessment included global health status, functional scales, and symptom burden during treatment. Results: Global health was significantly improved at the second and fourth cycles of 177Lu-PSMA RLT (P = 0.014 and P = 0.039, respectively). In line with this, role and emotional functioning showed significant improvements at the second and fourth treatment cycles (role functioning, P = 0.045 and P = 0.048, respectively, and emotional functioning, P = 0.035 and P = 0.007, respectively). In addition, compared with baseline, fatigue and pain were significantly alleviated at the second and fourth treatment cycles (pain, P = 0.035 and P = 0.034, respectively, and fatigue, P = 0.042 and P = 0.041, respectively). Other aspects of HRQoL, even if not significantly improved, remained stable over time, except for deterioration of fatigue at the study's end (P = 0.014) and reduction of dyspnea at the second treatment cycle (P = 0.012). Patients with early discontinuation of treatment showed a concordant decline in HRQoL. Conclusion: mCRPC patients showed significant improvement in HRQoL in the course of treatment with 177Lu-PSMA RLT. Furthermore, patients with early discontinuation of treatment showed an analogous decline in HRQoL.

Hsp70-A Universal Biomarker for Predicting Therapeutic Failure in Human Female Cancers and a Target for CTC Isolation in Advanced Cancers

Heat shock protein 70 (Hsp70) is frequently overexpressed in many different tumor types. However, Hsp70 has also been shown to be selectively presented on the plasma membrane of tumor cells, but not normal cells, and this membrane form of Hsp70 (mHsp70) could be considered a universal tumor biomarker. Since viable, mHsp70-positive tumor cells actively release Hsp70 in lipid micro-vesicles, we investigated the utility of Hsp70 in circulation as a universal tumor biomarker and its potential as an early predictive marker of therapeutic failure. We have also evaluated mHsp70 as a target for the isolation and enumeration of circulating tumor cells (CTCs) in patients with different tumor entities. Circulating vesicular Hsp70 levels were measured in the peripheral blood of tumor patients with the compHsp70 ELISA. CTCs were isolated using cmHsp70.1 and EpCAM monoclonal antibody (mAb)-based bead approaches and characterized by immunohistochemistry using cytokeratin and CD45-specific antibodies. In two out of 35 patients exhibiting therapeutic failure two years after initial diagnosis of non-metastatic breast cancer, progressively increasing levels of circulating Hsp70 had already been observed during therapy, whereas levels in patients without subsequent recurrence remained unaltered. With regards to CTC isolation from patients with different tumors, an Hsp70 mAb-based selection system appears superior to an EpCAM mAb-based approach. Extracellular and mHsp70 can therefore serve as a predictive biomarker for therapeutic failure in early-stage tumors and as a target for the isolation of CTCs in various tumor diseases.

[New tracers and combinations in radioligand therapy for prostate cancer]

BACKGROUND

¹⁷⁷Lutetium radioligand therapy directed against the prostate-specific membrane antigen (PSMA) is a new approved option for the treatment of metastatic, castration-resistant prostate cancer associated with a favorable toxicity profile.

OBJECTIVES

What are new or emerging developments in radioligand therapy for prostate cancer?

MATERIALS AND METHODS

A review of the current literature was performed.

RESULTS

The further development of radioligand therapy for prostate cancer is currently taking place primarily in the following areas: application in earlier stages of the disease, use of alternative isotopes, development and use of new ligands, search for new target structures and combination with other forms of therapy.

CONCLUSIONS

Radioligand therapy has become an integral part of the therapy algorithm in the treatment of metastatic, castration-resistant prostate cancer. Application in earlier stages of the disease is foreseeable. In the future, new ligands, alternative isotopes, new targets or combination therapies may increase efficacy and reduce toxicity.

Safety and Efficacy of [177Lu]-PSMA-I&T Radioligand Therapy in Octogenarians with Metastatic Castration-Resistant Prostate Cancer: Report on 80 Patients over the Age of 80 Years

¹⁷⁷Lu-labeled prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) is a new treatment option for metastatic castration-resistant prostate cancer (mCRPC). Its low toxicity profile favors use in elderly patients or in patients with critical comorbidities. The purpose of this analysis was to evaluate the efficacy and safety of [¹⁷⁷Lu]-PSMA RLT in mCRPC patients at least 80 y old. Methods: Eighty mCRPC patients at least 80 y old underwent [¹⁷⁷Lu]-PSMA-I&T RLT and were retrospectively selected. The patients were previously treated by androgen receptor-directed therapy, received taxane-based chemotherapy, or were chemotherapy-ineligible. The best prostate-specific antigen (PSA) response was calculated, as well as clinical progression-free survival (cPFS) and overall survival (OS). Toxicity data were acquired until 6 mo after the last treatment cycle. Results: Of 80 patients, 49 (61.3%) were chemotherapy-naïve and 16 (20%) had visceral metastases. The median number of previous mCRPC treatment regimens was 2. In total, 324 cycles (median, 4 cycles; range, 1-12) with a median cumulative activity of 23.8 GBq (interquartile range, 14.8-42.2) were applied. A PSA decline of 50% was achieved in 37 (46.3%) patients. Chemotherapy-naïve patients showed higher 50% PSA response rates than chemotherapy-pretreated patients (51.0% vs. 38.7%, respectively). Overall, median cPFS and OS were 8.7 and 16.1 mo, respectively. The median cPFS and OS of chemotherapy-naïve patients were significantly longer than those of chemotherapy-pretreated patients (10.5 vs. 6.5 mo and 20.7 vs. 11.8 mo, respectively, P < 0.05). A lower hemoglobin level and higher lactate dehydrogenase level at baseline were independent predictors of shorter cPFS and OS. Treatment-emergent grade 3 toxicities were anemia in 4 patients (5%), thrombocytopenia in 3 patients (3.8%), and renal impairment in 4 patients (5%). No nonhematologic grade 3 and no grade 4 toxicities were observed. The most frequent clinical side effects were grade 1-2 xerostomia, fatigue, and inappetence. Conclusion: [¹⁷⁷Lu]-PSMA-I&T RLT in mCRPC patients at least 80 y old is safe and effective, comparable to previously published data on non-age-selected cohorts with a low rate of high-grade toxicities. Chemotherapy-naïve patients showed a better and longer response to therapy than taxane-pretreated patients. [¹⁷⁷Lu]-PSMA RLT seems to be a meaningful treatment option for older patients.

The Impact of PSMA PET-Based Eligibility Criteria Used in the Prospective Phase II TheraP Trial in Metastatic Castration-Resistant Prostate Cancer Patients Undergoing Prostate-Specific Membrane Antigen-Targeted Radioligand Therapy

Prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) has shown encouraging results for treatment of metastatic castration-resistant prostate cancer (mCRPC) in the prospective, multicenter, randomized phase II TheraP study. The inclusion criteria for that study comprised a pretherapeutic ⁶⁸Ga-PSMA-11 PET scan showing sufficient tumor uptake using a predefined threshold and the absence of ¹⁸F-FDG-positive, PSMA ligand-negative tumor lesions. However, the prognostic value of these PET-based inclusion criteria remains unclear. Therefore, we evaluated the outcome of mCRPC patients treated with PSMA RLT using TheraP as well as other TheraP-based PET inclusion criteria. Methods: First, patients were dichotomized into 2 groups whose PSMA PET scans did (TheraP contrast-enhanced PSMA [cePSMA] PET-positive) or did not (TheraP cePSMA PET-negative) fulfill the inclusion criteria of TheraP. Notably, unlike in TheraP, ¹⁸F-FDG PET was not performed on our patients. Prostate-specific antigen (PSA) response (PSA decline ≥ 50% from baseline), PSA progression-free survival, and overall survival (OS) were compared. Additionally, patients were further dichotomized according to predefined SUV_max thresholds different from those used in TheraP to analyze their potential impact on outcome as well. Results: In total, 107 mCRPC patients were included in this analysis (TheraP cePSMA PET-positive, n = 77; TheraP cePSMA PET-negative, n = 30). PSA response rates were higher in TheraP cePSMA PET-positive patients than in TheraP cePSMA PET-negative patients (54.5% vs. 20%, respectively; P = 0.0012). The median PSA progression-free survival (P = 0.007) and OS (P = 0.0007) of patients were significantly longer in the TheraP cePSMA PET-positive group than in the TheraP cePSMA PET-negative group. Moreover, being in the TheraP cePSMA PET-positive group was identified as a significant prognosticator of longer OS (P = 0.003). The application of different SUV_max thresholds for a single hottest lesion demonstrated no influence on outcome in patients eligible for PSMA RLT. Conclusion: Patient selection for PSMA RLT according to the inclusion criteria of TheraP led to a better treatment response and outcome in our preselected patient cohort. However, a relevant number of patients not fulfilling these criteria also showed substantial rates of response.

177Lu-PSMA-I&T for Treatment of Metastatic Castration-Resistant Prostate Cancer: Prognostic Value of Scintigraphic and Clinical Biomarkers

The aim of this retrospective analysis was to determine prostate-specific antigen (PSA) response, PSA progression-free survival (PFS), and overall survival (OS) in a large cohort of patients with metastatic castration-resistant prostate cancer (mCRPC) treated with ¹⁷⁷Lu-PSMA-I&T and to identify clinical and scintigraphic prognostic factors for outcome. Methods: In total, 301 consecutive mCRPC patients were included in this analysis. Prognostic factors included clinical parameters, routine laboratory parameters, and findings on posttreatment scintigraphy. Scintigraphic tumor uptake of ¹⁷⁷Lu-PSMA-I&T was compared with salivary gland uptake and classified as high or low. The longest extent of skeletal metastatic disease was measured, and its changes during therapy were used to define scintigraphic progression, response, and stable disease. A PSA response of at least 50%, PSA PFS, and OS were calculated. Results: In total, 1,138 cycles (median, 3 cycles per patient) of ¹⁷⁷Lu-PSMA-I&T using a standard activity of 7.4 GBq were applied intravenously every 4-10 wk (median, 6 wk). Overall, 34% (95% CI, 28%-38%) of patients showed a PSA response of at least 50%, and the median PSA PFS and OS of the total patient cohort were 16.0 wk (95% CI, 12.1-19.9) and 13.8 mo (95% CI, 12.4-15.5), respectively. Patients with high scintigraphic tumor uptake showed a higher PSA response rate of at least 50% (45.7% vs. 10.4%; P < 0.0001) and a significantly reduced risk of PSA progression (median event time, 24.9 vs. 9.0 wk; hazard ratio, 0.3; 95% CI, 0.2-0.5; P < 0.0001). In our data, risk of death was not significantly different between patients with high scintigraphic uptake and those with low scintigraphic uptake (median, 14.4 vs. 12.4 mo; hazard ratio, 0.9; 95% CI, 0.6-1.3; P = 0.6). In a multivariable analysis, the following pretherapeutic prognostic factors for OS were identified: alkaline phosphatase, lactate dehydrogenase, and PSA levels; prior chemotherapy; and the presence of visceral metastases. Scintigraphic response was a strong prognostic factor for PSA response, PSA PFS, and OS after 1 treatment cycle. Conclusion: This retrospective analysis of a large group of consecutive patients corroborates previous clinical experience for ¹⁷⁷Lu-PSMA-I&T in mCRPC and establishes previously proposed prognostic factors. The skeletal tumor extent and its changes were identified as new potential biomarkers to predict the outcome of therapy after the first treatment cycle.

The prognostic role of 68Ga-PSMA11 PET-based response in prostate cancer patients undergoing taxane-based chemotherapy

To assess the prognostic utility of conventional biochemical and imaging response criteria and ⁶⁸Ga- prostate-specific membrane antigen (PSMA) 11 PET adapted or specific systems regarding overall survival (OS) in men with metastatic hormone-sensitive (mHSPC) and castration-resistant PC (mCRPC) treated with taxane-based chemotherapy. Methods: A total of 103 patients (pts) (n = 57 mHSPC, n = 46 mCRPC) underwent taxane-based chemotherapy. All patients had a minimum of two PSMA PET scans (at baseline and up to 3 months post-treatment). PSMA PET response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST 1.1), adapted Prostate Cancer Working Group Criteria 3 (aPCWG3, using PSMA PET instead of bone scan), adapted Positron Emission Tomography Response Criteria in Solid Tumors (aPERCIST) and PSMA PET Progression (PPP) criteria. Response by each criterion was stratified by either progressive disease (PD) versus non-PD. For aPERCIST, stratification by PD, stable disease (SD) and partial/complete remission (PR/CR) was performed. Biochemical response was determined by PSA decline ≥50%. Subgroup analyses were performed by castration-status. Univariable cox proportional hazard regression analyses including Harrell's concordance indices were calculated to investigate the association of PD by response criteria and OS. Kaplan-Meier tests including log-rank statistics were calculated for survival analyses. Results: 26 (25%) of pts had non-measurable disease by RECIST 1.1. PD by any response criterion was associated with an at least 2.5-fold increased risk of death and was highest for PD versus CR/PR by aPERCIST (HR 11.4) on univariable regression. Stratified by castration status, a similar pattern was observed. PD by any criterion as associated with significantly shortened OS across overall and subgroup analyses. PR/CR by aPERCIST identified pts with lower risk of death and longer OS as compared to patients with PD or SD. Conclusion: ⁶⁸Ga-PSMA11 PET-based response criteria (PPP, aPERCIST, aPCWG3) have high prognostic utility in men with metastatic PC undergoing taxane-based chemotherapy. PPP is simple to use, identified most patients with PD and showed best prognostic utility regarding OS. PR/CR by aPERCIST identifies a subgroup of responders (PR/CR) showing better outcomes than patients with PD or SD. Future studies are warranted to amend the current paradigm relying on mere differentiation of PD versus non-PD in metastatic PC and to identify true treatment responders by imaging criteria.

Prospectively Accelerated T2-Weighted Imaging of the Prostate by Combining Compressed SENSE and Deep Learning in Patients with Histologically Proven Prostate Cancer

BACKGROUND

To assess the performance of prospectively accelerated and deep learning (DL) reconstructed T2-weighted (T2w) imaging in volunteers and patients with histologically proven prostate cancer (PCa).

METHODS

Prospectively undersampled T2w datasets were acquired with acceleration factors of 1.7 (reference), 3.4 and 4.8 in 10 healthy volunteers and 23 patients with histologically proven PCa. Image reconstructions using compressed SENSE (C-SENSE) and a combination of C-SENSE and DL-based artificial intelligence (C-SENSE AI) were analyzed. Qualitative image comparison was performed using a 6-point Likert scale (overall image quality, noise, motion artifacts, lesion detection, diagnostic certainty); the T2 and PI-RADS scores were compared between the two reconstructions. Additionally, quantitative image parameters were assessed (apparent SNR, apparent CNR, lesion size, line profiles).

RESULTS

All C-SENSE AI-reconstructed images received a significantly higher qualitative rating compared to the C-SENSE standard images. Analysis of the quantitative parameters supported this finding, with significantly higher aSNR and aCNR. The line profiles demonstrated a significantly steeper signal change at the border of the prostatic lesion and the adjacent normal tissue in the C-SENSE AI-reconstructed images, whereas the T2 and PI-RADS scores as well as the lesion size did not differ.

CONCLUSION

In this prospective study, we demonstrated the clinical feasibility of a novel C-SENSE AI reconstruction enabling a 58% acceleration in T2w imaging of the prostate while obtaining significantly better image quality.

Novel Framework for Treatment Response Evaluation Using PSMA PET/CT in Patients with Metastatic Castration-Resistant Prostate Cancer (RECIP 1.0): An International Multicenter Study

Our objective was to develop version 1.0 of a novel framework for response evaluation criteria in prostate-specific membrane antigen (PSMA) PET/CT (RECIP) and a composite response classification that combines responses by prostate-specific antigen (PSA) measurements and by RECIP 1.0 (PSA + RECIP). Methods: This was an international multicenter, retrospective study. One hundred twenty-four men with metastatic castration-specific prostate cancer (mCRPC) who underwent 177Lu-PSMA therapy and received PSMA PET/CT at baseline and at an interim time point of 12 wk were included. Pairs of baseline interim PET/CT scans were interpreted by consensus among 3 masked readers for appearance of new lesions. Tumor lesions were segmented, and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP 1.0, which included classifications of complete response (RECIP-CR: absence of any PSMA-ligand uptake on interim PET/CT), partial response (RECIP-PR: decline ≥ 30% in PSMA-VOL and no appearance of new lesions), progressive disease (RECIP-PD: increase ≥ 20% in PSMA-VOL and appearance of new lesions), and stable disease (RECIP-SD: any condition but RECIP-PR or RECIP-PD). Changes in PSA levels at 12 wk by Prostate Cancer Working Group Criteria 3 were recorded. PSA + RECIP results were defined as response (PSA decline ≥ 50% or RECIP-PR/CR) or progression (PSA increase ≥ 25% or RECIP-PD). The study's primary outcome measure was the prognostic value of RECIP 1.0 for overall survival (OS). The secondary outcome measure was the prognostic accuracy (C-index) of PSA + RECIP versus PSA responses. Results: Patients with RECIP-PD (n = 39; 8.3 mo) had a shorter OS than patients with stable disease (RECIP-SD) (n = 47; 13.1 mo; P < 0.001) or RECIP-PR (n = 38; 21.7 mo; P < 0.001). In identifying responders and progressors, PSA + RECIP had C-indices superior to those of PSA only: 0.65 versus 0.62 (P = 0.028) and 0.66 versus 0.63 (P = 0.044), respectively. Conclusion: PSMA PET/CT by RECIP 1.0 is prognostic for OS and can be used as a response biomarker to monitor early efficacy of 177Lu-PSMA in men with mCRPC. PSA + RECIP may be used as a novel composite endpoint in mCRPC clinical trial design.

Pretherapeutic Comparative Dosimetry of 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T in Patients with Metastatic Castration-Resistant Prostate Cancer

Radiohybrid prostate-specific membrane antigen (rhPSMA) ligands allow for labeling with 18F and radiometals for endoradiotherapy. rhPSMA-7.3 has been designated as a lead compound with promising preclinical data for 177Lu-rhPSMA-7.3, which has shown higher tumor uptake than 177Lu-PSMA I&T. In this retrospective analysis, we compared pretherapeutic clinical dosimetry data of both PSMA ligands. Methods: Six patients with metastatic castration-resistant prostate cancer underwent both 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T pretherapeutic dosimetry. Whole-body scintigraphy was performed at 1 h, 4 h, 24 h, 48 h, and 7 d after injection. Regions of interest covering the whole body, organs, bone marrow, and tumor lesions were drawn for each patient. Absorbed doses for individual patients and pretherapeutic applications were calculated using OLINDA/EXM. To facilitate the comparison of both ligands, we introduced the therapeutic index (TI), defined as the ratio of mean pretherapeutic doses to tumor lesions over relevant organs at risk. Results: Mean whole-body pretherapeutic effective doses for 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T were 0.12 ± 0.07 and 0.05 ± 0.03 Sv/GBq, respectively. Mean absorbed organ doses for 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T were, for example, 1.65 ± 0.28 and 0.73 ± 0.18 Gy/GBq for the kidneys, 0.19 ± 0.09 and 0.07 ± 0.03 Gy/GBq for the liver, 2.35 ± 0.78 and 0.80 ± 0.41 Gy/GBq for the parotid gland, and 0.67 ± 0.62 and 0.30 ± 0.27 Gy/GBq for the bone marrow, respectively. Tumor lesions received mean absorbed doses of 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T of 6.44 ± 6.44 and 2.64 ± 2.24 Gy/GBq, respectively. The mean TIs for the kidneys were 3.7 ± 2.2 and 3.6 ± 2.2 for 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T, respectively, and those for the bone marrow were 15.2 ± 10.2 and 15.1 ± 10.2 for 177Lu-rhPSMA-7.3 and 177Lu-PSMA I&T, respectively. Conclusion: Pretherapeutic clinical dosimetry confirmed preclinical results of mean absorbed doses for tumors that were 2-3 times higher for 177Lu-rhPSMA-7.3 than for 177Lu-PSMA I&T. Absorbed doses to normal organs also tended to be higher for 177Lu-rhPSMA-7.3, resulting overall in similar average TIs for both radiopharmaceuticals with considerable interpatient variability. 177Lu-rhPSMA-7.3 has promise for a therapeutic efficacy similar to that of 177Lu-PSMA I&T at smaller amounts of injected activity, simplifying radiation safety measurements (especially for large patient numbers or dose escalation regimens).

[Update on systemic treatment of urothelial cancer: therapy in transition]

The systemic treatment of locally advanced and metastatic urothelial carcinoma has been changing at a breathtaking pace for a few years. However, platinum-based chemotherapy continues to be the central component of perioperative therapies and first-line treatment in the metastatic stage. Immunotherapies with immune checkpoint inhibitors are now an integral part of therapy algorithms. New targeted forms of chemotherapy are about to be approved. Advances in understanding the molecular genetic analysis of tumour tissue will soon enable personalised therapy options. This article is intended to provide an overview of current systemic therapy options and the underlying database. New developments are identified by presenting ongoing phase III trials. After reading this article, the reader should feel informed about the current status of systemic therapy for urothelial carcinoma.

Novel framework for treatment response evaluation using PSMA-PET/CT in patients with metastatic castration-resistant prostate cancer (RECIP): An international multicenter study

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Background: We aimed to develop a novel framework for Response Evaluation Criteria In PSMA-PET/CT (RECIP) 1.0 and a composite response classification which combines responses by PSA measurements and by RECIP 1.0 (PSA+RECIP). Methods: This was an international, multicenter, retrospective study. 124 men with mCRPC who underwent 177Lu-PSMA therapy and received PSMA-PET/CT at baseline (bPET) and at interim at 12 weeks (iPET) were included. Pairs of bPET and iPET were interpreted by consensus among three blinded readers for appearance of new lesions. Tumor lesions were segmented and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP 1.0, which was defined as: complete response (RECIP-CR: absence of any PSMA-ligand uptake on iPET), partial response (PSMA-PR: decline ≥30% in PSMA-VOL and no appearance of new lesions), progressive disease (RECIP-PD: increase ≥20% in PSMA-VOL and appearance of new lesions), stable disease (RECIP-SD: any condition but RECIP-PR or RECIP-PD). Changes in PSA levels at 12 weeks by PCWG3 were recorded. Responses by PSA+RECIP were defined as: response (PSA decline ≥50% or RECIP-PR/CR) and progression (PSA increase ≥25% or RECIP-PD). Study's primary outcome measure was the prognostic value of RECIP 1.0 for overall survival (OS). Secondary outcome measure was the prognostic accuracy (C-index) of PSA+RECIP vs PSA responses. Results: Patients with progressive disease (RECIP-PD; n=39; 8.3 mo) had shorter OS compared to patients with stable disease (RECIP-SD; n=47; 13.1 mo; p<0.001) and to those with partial response (RECIP-PR; n=38; 21.7 mo; p<0.001). PSA+RECIP had superior C-indices in identifying responders and progressors compared to PSA only: 0.65 vs 0.62 (p=0.028) and 0.66 vs 0.63 (p=0.044), respectively. Conclusions: PSMA-PET/CT by RECIP 1.0 is prognostic for OS and can be used as a response biomarker to monitor efficacy of 177Lu-PSMA in men with mCRPC. PSA+RECIP may be used as a novel composite endpoint in mCRPC clinical trial design.

Narrative review: prostate-specific membrane antigen-radioligand therapy in metastatic castration-resistant prostate cancer

Radioactive-labelled ligands targeting the prostate-specific membrane antigen (PSMA), a transmembrane protein overexpressed in prostate cancer (PC), have shown promising activity in treatment of metastatic castration-resistant prostate cancer (mCRPC). PSMA-617 and PSMA-I&T (imaging and therapy), both labeled to the beta-emitter lutetium-177 (Lu177), are most frequently used in clinical routine and have shown a favorable side-effect profile. Common side effects are transient xerostomia. Severe side effects, e.g., treatment-associated myelosuppression, are rare. Currently treatment with Lu177-PSMA outside clinical trials is available for compassionate use for patients who exhausted conventional therapies. Previous retro- and prospective studies reported promising results with ≥50% PSA declines observed in at least one third of patients. Retrospective data suggests worse biochemical response in patients with visceral metastases. Preliminary data from the randomized phase II (TheraP) trial showed an improved biochemical response rate of Lu177-PSMA as compared to cabazitaxel in patients progressing after docetaxel. Following these promising data, the results of the randomized, prospective phase III VISION study are eagerly anticipated. A major challenge remains resistance to radioligand therapy with Lu177-PSMA. As an alternative, a PSMA-ligand labeled to the alpha-emitter Actinium-225 (Ac-225) may be offered to patients, which shows promising activity in patients developing progression under Lu177-PSMA at the cost of higher toxicity. Mostly permanent xerostomia is a relevant side effect resulting in treatment discontinuation in up to a quarter of patients. This review summarizes the literature on activity and toxicity of PSMA-targeted radioligand therapy in mCRPC.

The need for cardiac surgery differential tariffs in Israel at the era of aging population and emerging technology: Importance of procedure type and patient complexity as assessed by EuroSCORE

Background

Reimbursement for cardiac surgical procedures in Israel is uniform and does not account for diversity in costs of various procedures or for diversity in patient mix. In an era of new and costly technology coupled with higher risk patients needing more complex surgery, these tariffs may not adequately reflect the true financial burden on the caregivers. In the present study we attempt to determine whether case mix and complexity of procedures significantly affect cost to justify differential tariffs.

Methods

We included all patients undergoing cardiac surgery at Shaare Zedek Medical Center between the years 1993–2016. Patients were stratified according to (1) type of surgery and (2) clinical profile as reflected by the predicted operative risk according to the European System for Cardiac Operative Risk Evaluation (EuroSCORE). Approximate cost of each group of patients was estimated by the average number of days in the Intensive Care Unit and days in the postoperative ward multiplied by the respective daily costs as determined by the Ministry of Health. We then added the fixed cost of the components used in the operating room (manpower and disposables). The final estimated cost (the outcome variable) was then evaluated as it relates to type of surgery and clinical profile. ANOVA was used to analyze cost variability between groups, and backward regression analysis to determine the respective effect of the abovementioned variables on cost. Because of non-normal distribution, both costs and lengths of stay were Log-transformed.

Results

Altogether there were 5496 patients: 3863, 836, 685 and 112 in the isolated CABG, CABG + valve, 1 valve and 2 valves replacement groups. By ANOVA, the costs in all EuroSCORE subgroups were significantly different from each other, increasing with increased EuroSCORE subgroup. Cost was also significantly different among procedure groups, increasing from simple CABG to single valve surgery to CABG + valve surgery to 2-valve surgery. In backward stepwise multiple regression analysis, both type of procedure and EuroSCORE group significantly impacted cost. ICU stay and Ward stay were significantly but weakly related while EuroSCORE subgroup was highly predictive of both ICU stay and ward stay.

Conclusions

The cost of performing heart surgery today is directly influenced by both patient profile as well as type of surgery, both of which can be quantified. Modern day technology is costly yet has become mandatory. Thus reimbursement for heart surgery should be based on differential criteria, namely clinical risk profile as well as type of surgery. Our results suggest an urgent need for design and implementation of a differential tariff model in the Israeli reimbursement system. We suggest that a model using a fixed, average price according to the type of procedure costs, in addition to a variable hospitalization cost (ICU + ward) determined by the patient EuroSCORE or EuroSCORE subgroup should enable an equitable reimbursement to hospitals, based on their case mix.

Nomograms to predict outcomes after 177Lu-PSMA therapy in men with metastatic castration-resistant prostate cancer: an international, multicentre, retrospective study

BACKGROUND

Lutetium-177 (¹⁷⁷Lu) prostate-specific membrane antigen (¹⁷⁷Lu-PSMA) is a novel targeted treatment for patients with metastatic castration-resistant prostate cancer (mCRPC). Predictors of outcomes after ¹⁷⁷Lu-PSMA to enhance its clinical implementation are yet to be identified. We aimed to develop nomograms to predict outcomes after ¹⁷⁷Lu-PSMA in patients with mCRPC.

METHODS

In this multicentre, retrospective study, we screened patients with mCRPC who had received ¹⁷⁷Lu-PSMA between Dec 10, 2014, and July 19, 2019, as part of the previous phase 2 trials (NCT03042312, ACTRN12615000912583) or compassionate access programmes at six hospitals and academic centres in Germany, the USA, and Australia. Eligible patients had received intravenous 6·0-8·5 GBq ¹⁷⁷Lu-PSMA once every 6-8 weeks, for a maximum of four to six cycles, and had available baseline [⁶⁸Ga]Ga-PSMA-11 PET/CT scan, clinical data, and survival outcomes. Putative predictors included 18 pretherapeutic clinicopathological and [⁶⁸Ga]Ga-PSMA-11 PET/CT variables. Data were collected locally and centralised. Primary outcomes for the nomograms were overall survival and prostate-specific antigen (PSA)-progression-free survival. Nomograms for each outcome were computed from Cox regression models with LASSO penalty for variable selection. Model performance was measured by examining discrimination (Harrell's C-index), calibration (calibration plots), and utility (patient stratification into low-risk vs high-risk groups). Models were validated internally using bootstrapping and externally by calculating their performance on a validation cohort.

FINDINGS

Between April 23, 2019, and Jan 13, 2020, 414 patients were screened; 270 (65%) of whom were eligible and were divided into development (n=196) and validation (n=74) cohorts. The median duration of follow-up was 21·5 months (IQR 13·3-30·7). Predictors included in the nomograms were time since initial diagnosis of prostate cancer, chemotherapy status, baseline haemoglobin concentration, and [⁶⁸Ga]Ga-PSMA-11 PET/CT parameters (molecular imaging TNM classification and tumour burden). The C-index of the overall survival model was 0·71 (95% CI 0·69-0·73). Similar C-indices were achieved at internal validation (0·71 [0·69-0·73]) and external validation (0·72 [0·68-0·76]). The C-index of the PSA-progression-free survival model was 0·70 (95% CI 0·68-0·72). Similar C-indices were achieved at internal validation (0·70 [0·68-0·72]) and external validation (0·71 [0·68-0·74]). Both models were adequately calibrated and their predictions correlated with the observed outcome. Compared with high-risk patients, low-risk patients had significantly longer overall survival in the validation cohort (24·9 months [95% CI 16·8-27·3] vs 7·4 months [4·0-10·8]; p<0·0001) and PSA-progression-free survival (6·6 months [6·0-7·1] vs 2·5 months [1·2-3·8]; p=0·022).

INTERPRETATION

These externally validated nomograms that are predictive of outcomes after ¹⁷⁷Lu-PSMA in patients with mCRPC might help in clinical trial design and individual clinical decision making, particularly at institutions where ¹⁷⁷Lu-PSMA is introduced as a novel therapeutic option.

FUNDING

Prostate Cancer Foundation.

Interim PSMA PET/CT for response evaluation during LuPSMA treatment in mCRPC (INTERIM PET): An explorative, multicenter study

5066

Background: The aim of this analysis was to evaluate the prognostic value of interim PSMA PET/CT in men with metastatic castration-resistant prostate cancer (mCRPC) treated with 177Lu-PSMA and to develop a novel framework for Response Evaluation Criteria In PSMA-imaging (RECIP). Methods: This was an explorative, multicenter, retrospective study; 124 men with mCRPC who underwent 177Lu-PSMA treatment and received PSMA-PET/CT at baseline (bPET) and at interim after two cycles of treatment (iPET) met the eligibility criteria and were included in this analysis. The primary endpoint was overall survival (OS). Pairs of bPET and iPET were interpreted by three independent readers for appearance of new lesions. Whole-body tumor lesions were segmented using qPSMA software and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Changes in PSMA-VOL on iPET relative to bPET were calculated. After being tested separately for associations with OS, appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP. Results: The median OS was 13.5 months (95%CI, 11.6-15.4). Appearance of at least one new lesion on iPET was observed in 73 (59%) patients and was associated with poor OS (hazard ratio [HR] 2.23; 95%CI, 1.51-3.28; P <.001). Based on the current data, RECIP were defined as: partial response (PSMA-PR) as a decline ≥20% in PSMA-VOL and no appearance of new lesions; progressive disease (PSMA-PD) as an increase ≥20% in PSMA-VOL and appearance of new lesions; stable disease (PSMA-SD) was defined as any condition but not PSMA-PR or PSMA-PD. The OS of men with PSMA-PD (n = 41) was significantly worse compared to men with PSMA-SD (n = 47; HR 2.52; 95%CI, 1.61–3.93; P <.001) and PSMA-PR (n = 36; HR 4.16; 95%CI, 2.54–6.78; P <.001). PSMA-SD was associated with significantly worse OS compared to PSMA-PR (HR 1.65; 95%CI, 1.02–2.65; P =.039). The time dependent C-index of associations with OS for response according to RECIP was 0.68 (95%CI, 0.63-0.72). Conclusions: Interim staging using PSMA-PET/CT and response classification by RECIP is prognostic for survival of men with mCRPC treated with 177Lu-PSMA. Validation of these findings in clinical trials is warranted.

Cytoreductive radical prostatectomy after chemohormonal therapy in patients with primary metastatic prostate cancer

Objective

Methods

Results

Conclusion

[Advanced prostate cancer: sequence of androgen receptor-targeted substances and chemotherapy determines long-term survival]

The treatment of advanced prostate cancer is changing. New study data and the resulting new therapeutic options have led to increasingly differentiated treatment decisions. Despite the changing therapy landscape, taxane-based chemotherapy-being a life-prolonging treatment-remains an indispensable therapeutic component for chemotherapy-fit patients in the metastatic setting. The current results of the randomized study CARD show that cabazitaxel has a higher oncological effectiveness, including a significant survival benefit and no negative impact on quality of life parameters, compared to a second androgen receptor targeted agent (ARTA) in patients with metastatic castration-resistant prostate cancer (mCRPC) who progressed after treatment with docetaxel and an androgen receptor-targeted agent (ARTA). In mCNPC the combination therapies of ADT (androgen deprivation therapy) plus docetaxel or of ADT plus ARTA have been established. In addition, three ARTAs tested in recent phase III studies in a clinical setting for patients with nonmetastatic castration-resistant prostate cancer (nmCRPC) showed that their use significantly prolongs metastasis-free survival and overall survival. The potential early use of ARTAs also has implications for the treatment of mCNPC. The aim of this publication is to provide guidance for clinical routine and to develop criteria for individual therapy decisions with a special focus on the use of chemotherapy.

First Experience Using 18F-Flubrobenguane PET Imaging in Patients with Suspected Pheochromocytoma or Paraganglioma

Pheochromocytomas and paragangliomas are a rare tumor entity originating from adrenomedullary chromaffin cells in the adrenal medulla or in sympathetic, paravertebral ganglia outside the medulla. Small lesions are especially difficult to detect by conventional CT or MRI and even by SPECT with the currently available radiotracers (e.g., metaiodobenzylguanidine [MIBG]). The novel PET radiotracer ¹⁸F-flubrobenguane could change the diagnostic paradigm in suspected pheochromocytomas and paragangliomas because of its homology with MIBG and the general advantages of PET imaging. The aim of this retrospective analysis was to evaluate ¹⁸F-flubrobenguane in pheochromocytomas and paragangliomas and to investigate the biodistribution in patients. Methods: Twenty-three patients with suspected pheochromocytoma or paraganglioma underwent PET/CT or PET/MRI at 63 ± 24 min after injection of 256 ± 33 MBq of ¹⁸F-flubrobenguane. The SUV_mean and SUV_max of organs were measured with spheric volumes of interest. Threshold-segmented volumes of interest were used to measure the SUV_mean or SUV_max of the tumor lesions. One reader evaluated all cross-sectional imaging datasets (CT or MRI) separately, as well as the PET hybrid datasets, and reported the lesion number and size. The diagnostic certainty for a positive lesion was scored on a 3-point scale. Results: ¹⁸F-flubrobenguane showed a reproducible, stable biodistribution, with the highest SUV_max and SUV_mean being in the thyroid gland (30.3 ± 2.2 and 22.5 ± 1.6, respectively), pancreas (12.2 ± 0.8 and 9.5 ± 0.7, respectively), and tumor lesions (16.8 ± 1.7 and 10.1 ± 1.1, respectively) and the lowest SUV_max and SUV_mean being in muscle (1.1 ± 0.06 and 0.7 ± 0.04, respectively) and the lung (2.5 ± 0.17 and 1.85 ± 0.13, respectively). In a subgroup analysis, a significantly higher average SUV_mean was seen for both pheochromocytoma and paraganglioma than for healthy adrenal glands (11.9 ± 2.0 vs. 9.9 ± 1.5 vs. 3.7 ± 0.2, respectively). In total, 47 lesions were detected. The reader reported more and smaller lesions with higher certainty in PET hybrid imaging than in conventional imaging; however, statistical significance was not reached. Of the 23 (23/47, 49%) lesions smaller than 1 cm, 61% (14/23) were found on hybrid imaging only. Conclusion: Our preliminary data suggest ¹⁸F-flubrobenguane PET to be a new, effective staging tool for patients with suspected pheochromocytoma or paraganglioma. Major advantages are the fast acquisition and high spatial resolution of PET imaging and the intense uptake in tumor lesions, facilitating detection. Further studies are warranted to define the role of ¹⁸F-flubrobenguane PET, particularly in comparison to standard diagnostic procedures such as MRI or ¹²³I-MIBG SPECT/CT.

Efficacy and Safety of 177Lu-labeled Prostate-specific Membrane Antigen Radionuclide Treatment in Patients with Diffuse Bone Marrow Involvement: A Multicenter Retrospective Study

The ¹⁷⁷Lu-labeled prostate-specific membrane antigen (LuPSMA) radionuclide therapy for metastatic castration-resistant prostate cancer is under investigation in a phase III trial (VISION: NCT03511664). However, patients with diffuse bone involvement, diagnosed with a "superscan" by bone scintigraphy at baseline, were excluded due to a lack of efficacy and safety data. We therefore aimed to investigate the feasibility of LuPSMA in patients with diffuse bone marrow involvement on baseline PSMA-targeted positron emission tomography. The primary end points were prostate-specific antigen (PSA) response (Prostate Cancer Working Group 3 [PCWG3]), hematologic safety profile (Common Terminology Criteria for Common Adverse Events [CTCAE]), and overall survival. Secondary end points of quality of life (assessed with Brief Pain Inventory-Short Form questionnaires) and radiologic response (Response Evaluation Criteria in Solid Tumors [RECIST]) were assessed. Through retrospective screening of databases, we identified 43 eligible patients across four centers worldwide who received 154 cycles of LuPSMA under clinical trials or compassionate access programs. Median baseline PSA was 1000 (interquartile range 431-2151) ng/ml. PSA decline of at least 50% at 12 wk was achieved in 22 (58%) patients, while median time to pain progression was 8.3 (95% confidence interval [CI] 4.1-12.6) mo. Median overall survival was 11.6 (95% CI 8.8-14.3) mo. Objective response in nodal or visceral disease was reported in seven (39%) of 18 patients with RECIST measurable disease. Grade 3 anemia, thrombocytopenia, and neutropenia occurred in nine (22%), seven (17%), and three (8%) patients, respectively. Grade 4 thrombocytopenia was noticed in three (8%) patients. In conclusion, patients with diffuse bone marrow involvement demonstrated similar LuPSMA efficacy and safety to phase II evidence. Acceptable safety outcomes do not support exclusion of patients with a superscan from future LuPSMA treatment protocols. PATIENT SUMMARY: In this report, we investigated the feasibility of prostate-specific membrane antigen (PSMA)-directed radionuclide treatment in patients with metastatic castration-resistant prostate cancer and diffuse bone involvement. We found that, despite a high load of bone metastases, PSMA-targeted therapy remains efficacious and safe when compared with the current phase II trial results.

PSMA-PET/CT-based Lymph Node Atlas for Prostate Cancer Patients Recurring After Primary Treatment: Clinical Implications for Salvage Radiation Therapy

BACKGROUND

Many patients experience recurrence of prostate cancer after radical prostatectomy.

OBJECTIVE

The aim of this study was to visually analyze typical patterns of lymph node (LN) involvement for prostate cancer (PC) patients with biochemical recurrence after radical prostatectomy and lymphadenectomy by creating a color-coded heat map using gallium-68 prostate-specific membrane antigen positron emission tomography (⁶⁸Ga-PSMA-PET) imaging. Further, we evaluated which LNs were covered by the Radiation Therapy Oncology Group (RTOG) clinical target volume (CTV) contouring guidelines.

DESIGN, SETTING, AND PARTICIPANTS

A total of 1653 ⁶⁸Ga-PSMA-PET/computed tomography (CT) datasets were screened retrospectively. After meeting the eligibility criteria, 233 patients with 799 LN metastases were included in our study.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We created a comprehensive three-dimensional color-coded LN atlas. Further, the coverage of LN metastases by RTOG CTV was assessed and stratification for risk factors was performed.

RESULTS AND LIMITATIONS

In the overall, mainly high risk, collective, complete coverage by the standard RTOG CTV was accomplished in 31.0% of all LN metastases. The vast majority of uncovered LNs are situated in the para-aortal, pararectal, paravesical, preacetabular, presacral, and inguinal regions. Concerning examined stratification factors, prostate-specific antigen (PSA) levels at the time of PET/CT imaging had the highest predictive value for extrapelvic metastatic LN spread. Every increase of 1 ng/mL in PSA raises the risk of metastases outside the CTV by a factor of 1.43.

CONCLUSIONS

We developed the first LN atlas for patients with recurrent PC using a heat map technique, in order to illustrate hot spots of LN recurrence. The vast majority of detected LNs are not covered by a standard CTV as recommended by the RTOG. Application of the standard RTOG CTV for pelvic irradiation in the salvage setting for high-risk PC patients seems to be inappropriate.

PATIENT SUMMARY

We visualized typical lymph node recurrence sites for patients after prostate cancer surgery.

Prognostic markers for overall survival and outcome to LuPSMA radionuclide treatment in patients with metastatic castration-resistant prostate cancer

5548

Background: The aim of this international multicenter retrospective analysis was to identify prognostic markers for the clinical outcome in late-stage mCRPC patients treated with 177Lutetium-prostate-specific membrane antigen (LuPSMA) radionuclide treatment. Methods: Patients with progressive mCRPC treated with LuPSMA at six centers in Germany, USA, and Australia were considered for inclusion. Eligible patients had 24 predefined, pretherapeutic covariates (demographics, prior mCRPC treatments, and PSMA PET/CT derived parameters) and survival data available. Endpoints included overall survival (OS) and PSA progression-free survival (PSA-PFS). Covariates were tested using univariate and mulitvariate proportional hazards regression Cox models. Results: 267/414 (64%) patients met inclusion criteria and were analyzed. 113 patients participated in clinical trials (ACTRN12615000912583, NCT03042312), while 154 were enrolled in compassionate-access programs. After a median follow-up of 22.5 months, median OS was 13.0 months (95%CI 11.6-14.4); 83% of the patients died. Median PSA-PFS was 4.0 months (95%CI 3.2-4.7). In the multivariate analysis, factors associated with shorter OS were: shorter time since diagnosis of prostate cancer (HR=2.04; p=0.002), lower number of prior systemic therapies (≤3; HR=1.56; p=0.006), prior exposure to chemotherapy (HR=1.42; p=0.05), lower hemoglobin levels (HR=1.13; p=0.002), higher number of lesions (≥20: HR=1.53; p=0.009), multiple sites of metastases (bone/LN only vs. bone + LN; HR=1.39; p=0.03) and visceral involvement (M1c) (HR=1.45; p=0.01). Factors associated with longer PSA-PFS were: longer time since diagnosis of prostate cancer (HR=0.44; p<0.001), higher hemoglobin levels (HR=0.32; p=0.03), presence of pelvic lymph nodes (LN) metastasis (N1) (HR=0.68; p=0.01), no distant lymph node metastases (M1a) (HR=0.66; p=0.01), no skeleton involvement (HR=0.44; p=0.01), no visceral metastases (M1c) (HR=0.51; p<0.001), higher PSMA-positive tumor volume (HR=0.87; p=0.04), and higher SUVmean (HR=0.94; p=0.002). Conclusions: This retrospective analysis identified prognostic factors for survival and treatment response to LuPSMA. Along with the conventional risk factors in mCRPC, PSMA PET/CT can be a useful tool for stratifying patients and guide patient’s selection for LuPSMA radionuclide treatment.

Efficacy and safety of 177Lu-PSMA radionuclide treatment in patients with diffuse bone marrow involvement: A multicenter retrospective study

e17543

Background: 177Lu-labelled prostate-specific membrane antigen (LuPSMA) radionuclide therapy of metastatic castration-resistant prostate cancer (mCRPC) is currently under investigation in phase III trial (VISION). However, patients with diffuse bone involvement, diagnosed with a superscan by bone scintigraphy at baseline, were excluded due to lack of efficacy and safety data. We therefore aimed to investigate the feasibility of LuPSMA in patients with diffuse bone marrow involvement on baseline PSMA-targeted PET/CT. Methods: Patients with progressive mCRPC treated with LuPSMA at six centers in Germany, USA and Australia were considered for inclusion.Eligible patients had 50% or greater bone involvement of the axial skeleton on the baseline PSMA PET. The primary endpoints were PSA response (PCWG3), toxicity (CTCAE v4.02), and overall survival (OS). Secondary endpoints included quality of life (assessed with Brief Pain Inventory-Short Form questionnaires) and radiological response (as measured by CT using RECIST 1.1). Results: 43 of 352 (12%) screened patients met inclusion criteria and were retrospectively analyzed. Median baseline PSA was 1000 (IQR 431-2151) ng/ml. PSA decline ≥50% was achieved in 26/43 (65%) patients, while median PSA progression-free survival was 4.8 (95%CI 2.4–7.1) mo. 15/42 (36%) evaluable patients exhibited pain progression with a median time-to-pain progression of 8.3 (95%CI 5.4–11.3) mo. After a median follow-up of 18.9 mo, median OS was 11.6 (95%CI 8.8-14.3) mo. Objective response in nodal or visceral disease was reported in 7/18 (39%) patients with evaluable target lesions on CT. Grade 3/4 anemia, thrombocytopenia and neutropenia occurred in 9/43 (21%), 10/43 (23%) and 3/43 (8%) patients, respectively. Of note, all patients had grade 1 anemia at baseline, with a median hemoglobin of 9.6 g/dl. 2/43 (5%) patients experienced an adverse event that required a reduction to the LuPSMA activity beginning with the third cycle. Conclusions: Patients with diffuse bone marrow involvement demonstrate similar LuPSMA efficacy and safety when compared to phase II evidence. Acceptable safety outcomes do not support exclusion of patients with a superscan from future LuPSMA treatment protocols.

Early Prostate-Specific Antigen Changes and Clinical Outcome After 177Lu-PSMA Radionuclide Treatment in Patients with Metastatic Castration-Resistant Prostate Cancer

Prostate-specific antigen (PSA) is widely used to monitor treatment response in patients with metastatic castration-resistant prostate cancer. However, PSA measurements are considered only after 12 wk of treatment. We aimed to evaluate the prognostic value of early PSA changes after ¹⁷⁷Lu-labeled prostate-specific membrane antigen (¹⁷⁷Lu-PSMA) radionuclide treatment in metastatic castration-resistant prostate cancer patients. Methods: Men who were treated with ¹⁷⁷Lu-PSMA under a compassionate-access program at our institution and had available PSA values at baseline and at 6 wk after treatment initiation were included in this retrospective analysis. Patients were assigned to 3 groups on the basis of PSA changes: response (≥30% decline), progression (≥25% increase), and stable (<30% decline and <25% increase). The coprimary endpoints were overall survival and imaging-based progression-free survival. The secondary endpoints were PSA changes at 12 wk and PSA flare-up. Results: We identified 124 eligible patients with PSA values at 6 wk. A greater than or equal to 30% decline in PSA at 6 wk was associated with longer overall survival (median, 16.7 mo; 95% CI, 14.4-19.0) than stable PSA (median, 11.8 mo; 95% CI, 8.6-15.1) (P = 0.007) or PSA progression (median, 6.5 mo; 95% CI, 5.2-7.8) (P < 0.001). Patients with a greater than or equal to 30% decline in PSA at 6 wk also had a lower risk of imaging-based progression than patients with stable PSA (hazard ratio, 0.60; 95% CI, 0.38-0.94) (P = 0.02), whereas patients with PSA progression had a higher risk of imaging-based progression than patients with stable PSA (hazard ratio, 3.18; 95% CI, 1.95-5.21) (P < 0.001). The percentage changes in PSA at 6 and 12 wk were highly associated (r = 0.90; P < 0.001). Of 31 patients who experienced early PSA progression at 6 wk, 29 (94%) showed biochemical progression at 12 wk. Overall, only 1 (3%) of 36 patients with PSA progression at 6 wk achieved any PSA decline at 12 wk (1% of the entire cohort). The limitations of the study included its retrospective nature and the single-center experience. Conclusion: PSA changes at 6 wk after ¹⁷⁷Lu-PSMA initiation are an early indicator of long-term clinical outcome. Patients with PSA progression after 6 wk of treatment could benefit from a very early decision to switch treatment. PSA flare-up during ¹⁷⁷Lu-PSMA treatment is very uncommon. Prospective studies are now warranted to validate our findings and potentially inform clinicians earlier on the effectiveness of ¹⁷⁷Lu-PSMA.

Multicentric analytical comparability study of programmed death-ligand 1 expression on tumor-infiltrating immune cells and tumor cells in urothelial bladder cancer using four clinically developed immunohistochemistry assays

Programmed death-ligand 1 (PD-L1) expression on tumor cells (TC) or tumor-infiltrating immune cells (IC) correlated in several studies with PD-L1/programmed death-1 (PD-1) checkpoint inhibitor efficacy. Since June 2018, a positive PD-L1 status is required for atezolizumab or pembrolizumab treatment of patients with advanced or metastasized urothelial bladder cancer, who are ineligible for cisplatin-containing therapy. We examined technical comparability and inter-reader agreement of four clinically developed PD-L1 assays in locally advanced disease. Archived, formalin-fixed, paraffin-embedded sections from 30 patients (73.3% cystectomies, 26.7% transurethral resections) were stained by PD-L1 immunohistochemistry using VENTANA SP142, VENTANA SP263, DAKO 22C3, and DAKO 28-8 at two sites per manufacturers’ protocols and scored blinded at five sites for PD-L1 expression on IC (% per tumor area) and TC (%). Small, non-significant inter-assay differences were observed for IC. For TC, SP142 showed significantly lower staining percentages. Pairwise comparisons revealed − 0.3 to 1.6% differences in adjusted means between assays for IC, and for TC, − 10.5 to − 7.8% (SP142 versus others) and − 1.9 to 2.7% (other comparisons). Inter-reader and inter-assay agreement was moderate to high for both IC and TC. Allocation to binary cutoffs (1%, 5%, 10%) showed substantial to high Kappa agreement scores (0.440–0.923) for IC and TC between assays for each reader. This first multicenter study, with five independent readers blinded with respect to the assay used, suggests that all four currently clinically relevant assays are analytically similar for evaluation of PD-L1-stained IC and three (SP263, 22C3, and 28-8) for PD-L1-stained TC. Inter-observer agreement for trained readers in scoring of both IC and TC positivity was generally high.

Early Experience of Rechallenge 177Lu-PSMA Radioligand Therapy After an Initial Good Response in Patients with Advanced Prostate Cancer

Our aim was to retrospectively evaluate the feasibility of rechallenge ¹⁷⁷Lu-prostate-specific membrane antigen (¹⁷⁷Lu-PSMA) radioligand therapy. Methods: Rechallenge radioligand therapy was defined as subsequent treatment with ¹⁷⁷Lu-PSMA after initial exposure with an excellent response followed by progression. Biochemical, radiographic, clinical antitumor response, and adverse events were analyzed. Prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival were calculated. Results: Eight patients underwent a median of 2 (range: 1-4) cycles of rechallenge with ¹⁷⁷Lu-PSMA for imaging and therapy. A maximum PSA decrease of 50% was achieved in 3 patients (37.5%). Radiographic response was favorable in 3 patients, whereas 4 exhibited progressive disease. Eastern Cooperative Oncology Group performance status was stable during therapy in all patients. No grade 4 toxicity was noticed, and grade 3 toxicity occurred in 3 patients (37.5%). The median PSA-PFS and overall survival were 3.2 mo (95% confidence interval, 2.6-3.7 mo) and 14.0 mo (95% confidence interval, 6.2-21.8 mo), respectively. Conclusion: In a small patient cohort with an initial excellent response, ¹⁷⁷Lu-PSMA rechallenge is still active, with lower efficacy and higher toxicity.

Use of Hepatocytes in Adhesion and Suspension Cultures for Liver Support Bioreactors

Hepatocyte cultivation in bioreactors for hybrid liver support systems is possible under two conditions: attached to a substrate like membranes or microcarriers or in suspension culture. To compare the ammonia metabolism of hepatocytes cultivated under these two conditions, cultures of primary seeded rat hepatocytes were cultivated either attached to collagen coated tissue culture plastic or as a suspension culture.

During the time course of culture, the ability of hepatocytes to reduce the ammonia content of the medium decreased in both adhesion and suspension cultures, though to different extents.

In suspension cultures, ammonia content was reduced from 350 μM to about 100 μM (day 4) and to about 180 μM (day 6). No significant reduction was seen on day 8 of culture. In contrast, hepatocytes attached to collagen coated dishes remained viable and functional for at least 8 days after plating, reducing ammonia content from 350 μM to 70 μM (day 4), 90 μM (day 6) and 180 μM (day 8). The period of useful metabolism of hepatocytes in bioreactors for hybrid liver support systems appears to depend on the culture conditions

Hyperkalemia in patients treated with endoradiotherapy combined with amino acid infusion is associated with severe metabolic acidosis

Background

Amino acid co-infusion for renal protection in endoradiotherapy (ERT) applied as prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) or peptide receptor radionuclide therapy (PRRT) has been shown to cause severe hyperkalemia. The pathophysiology behind the rapid development of hyperkalemia is not well understood. We hypothesized that the hyperkalemia should be associated with metabolic acidosis.

Results

Twenty-two patients underwent ERT. Prior to the first cycle, excretory kidney function was assessed by mercapto-acetyltriglycine (MAG-3) renal scintigraphy, serum biochemistry, and calculated glomerular filtration rate (eGFR). All patients received co-infusion of the cationic amino acids L-arginine and L-lysine for nephroprotection. Clinical symptoms, electrolytes, and acid-base status were evaluated at baseline and after 4 h.

No patient developed any clinically relevant side effects. At baseline, acid base status and electrolytes were normal in all patients. Excretory kidney function was normal or only mildly impaired in all except two patients with stage 3 renal insufficiency. All patients developed hyperkalemia. Base excess and HCO₃⁻ were significantly lower after 4 h. In parallel, mean pH dropped from 7.36 to 7.29. There was a weak association between calculated (r = − 0.21) as well as MAG-3-derived GFR (r = − 0.32) and the rise in potassium after 4 h.

Conclusion

Amino acid co-infusion during ERT leads to severe metabolic acidosis which induces hyperkalemia by potassium hydrogen exchange. This novel finding implies that commercially available bicarbonate solutions might be an easy therapeutic option to correct metabolic acidosis rapidly.

Electronic supplementary material

The online version of this article (10.1186/s13550-018-0370-z) contains supplementary material, which is available to authorized users.

Clinical experience with 100 consecutive patients treated with Lu-177-labeled PSMA-I&T radioligand therapy for metastatic castration-resistant prostate cancer

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Background: To report our clinical experience with 177Lutetium-labeled prostate-specific membrane antigen-ligand (177Lu-PSMA-I&T) for systemic radioligand therapy in 100 consecutive patients with metastatic castration-resistant prostate cancer (mCRPC). Methods: All patients were treated under a review board-approved compassionate use protocol. Eligibility criteria for 177Lu-PSMA-I&T therapy included previous treatment with abiraterone or enzalutamide, previous taxane-based chemotherapy or unsuitability for taxanes as well as positive 68Ga-PSMA tracer uptake of metastases in a prior PET-scan. Intravenous treatment with 177Lu-PSMA-I&T was given 6- to 8-weekly with an activity of 7.4GBq up to 6 cycles in patients without clinical or radiographic progression. We report prostate-specific antigen (PSA) decline, PSA progression-free survival (PSA-PFS), clinical progression-free survival (cPFS) and overall survival (OS) as well as toxicity. Results: Median age was 72 years (range 46-85) and median PSA level was 164 ng/ml (range 0-6178). Bone, lymph node and visceral metastases were present in 94%, 85% and 33% of patients, respectively. The median number of previous treatment regimens for mCRPC was 3 (range 1-6) and 84% of patients were pretreated with chemotherapy. At the time of evaluation, 286 cycles with 177Lu-PSMA-I&T were applied (median 2 cycles per patient, range 1-6), while treatment was still ongoing in 27% of patients. Overall, 4 and 6 cycles were applied in 33 and 15 patients, respectively. PSA decline ≥30%, ≥50% and ≥90% was achieved in 40%, 32% and 9% of patients, respectively. Median PSA-PFS was 3.4 months (95%CI 2.7-4.0), median cPFS was 4.1 months (95%CI 2.5-5.7) and median OS was 12.2 months (95%CI 8.8-15.7). Treatment-emergent hematologic grade 3/4 toxicities were anemia in 7%, thrombocytopenia in 5% and neutropenia in 4% of patients. Grade 3/4-non-hematologic toxicities were not observed. The main non-hematologic grade 1/2 toxicities were dry mouth in 18%, fatigue in 16% and loss of appetite in 9/% of patients. Conclusions: Radioligand therapy with 177Lu-PSMA I&T appears to be safe and active in late-stage mCRPC.

The Effect of Total Tumor Volume on the Biologically Effective Dose to Tumor and Kidneys for 177Lu-Labeled PSMA Peptides

The aim of this work was to simulate the effect of prostate-specific membrane antigen (PSMA)-positive total tumor volume (TTV) on the biologically effective doses (BEDs) to tumors and organs at risk in patients with metastatic castration-resistant prostate cancer who are undergoing ¹⁷⁷Lu-PSMA radioligand therapy. Methods: A physiologically based pharmacokinetic model was fitted to the data of 13 patients treated with ¹⁷⁷Lu-PSMA I&T (a PSMA inhibitor for imaging and therapy). The tumor, kidney, and salivary gland BEDs were simulated for TTVs of 0.1-10 L. The activity and peptide amounts leading to an optimal tumor-to-kidneys BED ratio were also investigated. Results: When the TTV was increased from 0.3 to 3 L, the simulated BEDs to tumors, kidneys, parotid glands, and submandibular glands decreased from 22 ± 15 to 11.0 ± 6.0 Gy_1.49, 6.5 ± 2.3 to 3.7 ± 1.4 Gy_2.5, 11.0 ± 2.7 to 6.4 ± 1.9 Gy_4.5, and 10.9 ± 2.7 to 6.3 ± 1.9 Gy_4.5, respectively (where the subscripts denote that an α/β of 1.49, 2.5, or 4.5 Gy was used to calculate the BED). The BED to the red marrow increased from 0.17 ± 0.05 to 0.32 ± 0.11 Gy₁₅ For patients with a TTV of more than 0.3 L, the optimal amount of peptide was 273 ± 136 nmol and the optimal activity was 10.4 ± 4.4 GBq. Conclusion: This simulation study suggests that in patients with large PSMA-positive tumor volumes, higher activities and peptide amounts can be safely administered to maximize tumor BEDs without exceeding the tolerable BED to the organs at risk.

[PSMA-targeted radioligand therapy in prostate cancer]

Radioligand therapy (RLT) directed against prostate-specific membrane antigen (PSMA) enables tumor-specific treatment directed against PSMA-overexpressing prostate cancer cells. Several PSMA ligands such as PSMA-617 or PSMA-I&T have been developed that can be labeled with β‑radiating lutetium-177. These are currently applied in compassionate use programs to treat metastatic castration-resistant prostate cancer (mCRPC). PSMA-directed RLT is currently being offered in several nuclear medicine departments throughout Germany. Several retrospective case series demonstrate its activity with a prostate-specific antigen (PSA) decrease >50% in 30-60% of mCRPC patients. The toxicity seems to be low. Hematologic grade 4 toxicity has not been observed and grade 3 toxicities rarely occur. The main nonhematologic adverse events are intermittent dry mouth because of unspecific PSMA expression in the salivary glands as well as fatigue and nausea. Currently there are no prospective studies available for evaluation of PSMA-targeted RLT and a survival benefit over approved standard therapies such as abiraterone, enzalutamide, radium-223-dichloride, docetaxel or cabazitaxel has not been shown. PSMA-targeted RLT should therefore currently only be offered after critical evaluation in patients who exhausted the approved standard therapies.

AR-V7 in Peripheral Whole Blood of Patients with Castration-resistant Prostate Cancer: Association with Treatment-specific Outcome Under Abiraterone and Enzalutamide

BACKGROUND

It has been demonstrated that androgen receptor splice variant 7 (AR-V7) expression in circulating tumor cells (CTCs) predicts poor treatment response in metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone or enzalutamide.

OBJECTIVE

To develop a practical and robust liquid profiling approach for direct quantification of AR-V7 in peripheral whole blood without the need for CTC capture and to determine its potential for predicting treatment response in mCRPC patients.

DESIGN, SETTING, AND PARTICIPANTS

Whole blood samples from a prospective biorepository of 85 mCRPC patients before treatment initiation with abiraterone (n=56) or enzalutamide (n=29) were analyzed via droplet digital polymerase chain reaction.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The association of AR-V7 status with prostate-specific antigen (PSA) response defined by PSA decline ≥50% and with PSA-progression-free survival (PSA-PFS), clinical PFS, and overall survival (OS) was assessed.

RESULTS AND LIMITATIONS

High AR-V7 expression levels in whole blood were detectable in 18% (15/85) of patients. No patient with high AR-V7 expression achieved a PSA response, and AR-V7 status was an independent predictor of PSA response in multivariable logistic regression analysis (p=0.03). High AR-V7 expression was associated with shorter PSA-PFS (median 2.4 vs 3.7 mo; p<0.001), shorter clinical PFS (median 2.7 vs 5.5 mo; p<0.001), and shorter OS (median 4.0 vs. 13.9 mo; p<0.001). On multivariable Cox regression analysis, high AR-V7 expression remained an independent predictor of shorter PSA-PFS (hazard ratio [HR] 7.0, 95% confidence interval [CI] 2.3-20.7; p<0.001), shorter clinical PFS (HR 2.3, 95% CI 1.1-4.9; p=0.02), and shorter OS (HR 3.0, 95% CI 1.4-6.3; p=0.005).

CONCLUSIONS

Testing of AR-V7 mRNA levels in whole blood is a simple and promising approach to predict poor treatment outcome in mCRPC patients receiving abiraterone or enzalutamide.

PATIENT SUMMARY

We established a method for determining AR-V7 status in whole blood. This test predicted treatment resistance in patients with metastatic castration-resistant prostate cancer undergoing treatment with abiraterone or enzalutamide. Prospective validation is needed before application to clinical practice.

[The role of immunooncology in the treatment of urothelial cancer]

Data published in November 2016 showed a significant survival benefit for the PD-1 antibody Pembrolizumab in the second-line treatment of metastatic urothelial cancer in comparison to standard chemotherapy. Other PD-1/PD-L1 antibodies are being tested in advanced clinical trials. This class of substances will become standard of care from the time of their approval which is expected for 2017 and will replace vinflunine, which is currently recommended in the German guideline. PD-1/PD-L1 directed substances are also being tested as a first line treatment of metastatic urothelial carcinoma. Monotherapy is evaluated as well as combination treatments with CTLA-4 inhibitors of conventional chemotherapy. First data are expected at the end of 2017.A new strategy is the application of PD-1/PD-L1 directed substances in the perioperative treatment of patients with a muscle-invasive urothelial carcinoma after complete surgical resection (cystectomy or nephroureterectomy). Two international phase III trials evaluate an adjuvant immunotherapy with nivolumab and atezolizumab. Recruitment will be completed in 2018.

Exploring New Multimodal Quantitative Imaging Indices for the Assessment of Osseous Tumor Burden in Prostate Cancer Using 68Ga-PSMA PET/CT

PET combined with CT and prostate-specific membrane antigen (PSMA) ligands has gained significant interest for staging prostate cancer (PC). In this study, we propose 2 multimodal quantitative indices as imaging biomarkers for the assessment of osseous tumor burden using ⁶⁸Ga-PSMA PET/CT and present preliminary clinical data. Methods: We defined 2 bone PET indices (BPIs) that incorporate anatomic information from CT and functional information from ⁶⁸Ga-PSMA PET: BPI_VOL is the percentage of bone volume affected by tumor and BPI_SUV additionally considers the level of PSMA expression. We describe a semiautomatic computation method based on segmentation of bones in CT and of lesions in PET. Data from 45 patients with castration-resistant PC and bone metastases during ²²³Ra-dichloride were retrospectively analyzed. We evaluated the computational stability and reproducibility of the proposed indices and explored their relation to the prostate-specific antigen blood value, the bone scan index (BSI), and disease classification using PERCIST. Results: On the technical side, BPI_VOL and BPI_SUV showed an interobserver maximum difference of 3.5%, and their computation took only a few minutes. On the clinical side, BPI_VOL and BPI_SUV showed significant correlations with BSI (r = 0.76 and 0.74, respectively, P < 0.001) and prostate-specific antigen values (r = 0.57 and 0.54, respectively, P < 0.01). When the proposed indices were compared against expert rating using PERCIST, BPI_VOL and BPI_SUV showed better agreement than BSI, indicating their potential for objective response evaluation. Conclusion: We propose the evaluation of BPI_VOL and BPI_SUV as imaging biomarkers for ⁶⁸Ga-PSMA PET/CT in a prospective study exploring their potential for outcome prediction in patients with bone metastases from PC.

[Bone-specific therapy with radium-223 dichloride : Castration-resistant prostate cancer with symptomatic bone metastases]

Radium-223 dichloride (Xofigo®, Alpharadin) is approved for the treatment of metastatic castration-resistant prostate cancer with symptomatic bone metastases and no known visceral metastases. As a calcium mimetic, it is integrated into osteoplastic bone lesions and emits alpha particles with high energy which leads to local destruction of tumor cells. In the 2013 published ALSYMPCA trial, a significant advantage for overall survival and quality of life in comparison to placebo was found. Recent data suggest an increased potential in combination with next generation hormonal treatment.

Radiation Dosimetry for 177Lu-PSMA I&T in Metastatic Castration-Resistant Prostate Cancer: Absorbed Dose in Normal Organs and Tumor Lesions

Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy is increasingly used in metastatic castration-resistant prostate cancer. We aimed to estimate the absorbed doses for normal organs and tumor lesions using ¹⁷⁷Lu-PSMA I&T (I&T is imaging and therapy) in patients undergoing up to 4 cycles of radioligand therapy. Results were compared with pretherapeutic Glu-NH-CO-NH-Lys-(Ahx)-[⁶⁸Ga(HBEDCC)] (⁶⁸Ga-PSMA-HBED-CC) PET. Methods: A total of 34 cycles in 18 patients were analyzed retrospectively. In 15 patients the first, in 9 the second, in 5 the third, and in 5 the fourth cycle was analyzed, respectively. Whole-body scintigraphy was performed at least between 30-120 min, 24 h, and 6-8 d after administration. Regions of interest covering the whole body, organs, and up to 4 tumor lesions were drawn. Organ and tumor masses were derived from pretherapeutic ⁶⁸Ga-PSMA-HBED-CC PET/CT. Absorbed doses for individual cycles were calculated using OLINDA/EXM. SUVs from pretherapeutic PET were compared with absorbed doses and with change of SUV. Results: The mean whole-body effective dose for all cycles was 0.06 ± 0.03 Sv/GBq. The mean absorbed organ doses were 0.72 ± 0.21 Gy/GBq for the kidneys; 0.12 ± 0.06 Gy/GBq for the liver; and 0.55 ± 0.14 Gy/GBq for the parotid, 0.64 ± 0.40 Gy/GBq for the submandibular, and 3.8 ± 1.4 Gy/GBq for the lacrimal glands. Absorbed organ doses were relatively constant among the 4 different cycles. Tumor lesions received a mean absorbed dose per cycle of 3.2 ± 2.6 Gy/GBq (range, 0.22-12 Gy/GBq). Doses to tumor lesions gradually decreased, with 3.5 ± 2.9 Gy/GBq for the first, 3.3 ± 2.5 Gy/GBq for the second, 2.7 ± 2.3 Gy/GBq for the third, and 2.4 ± 2.2 Gy/GBq for the fourth cycle. SUVs of pretherapeutic PET moderately correlated with absorbed dose (r = 0.44, P < 0.001 for SUV_max; r = 0.43, P < 0.001 for SUV_mean) and moderately correlated with the change of SUV (r = 0.478, P < 0.001 for SUV_max, and r = 0.50, P < 0.001 for SUV_mean). Conclusion: Organ- and tumor-absorbed doses for ¹⁷⁷Lu-PSMA I&T are comparable to recent reports and complement these with information on an excellent correlation between the 4 therapy cycles. With the kidneys representing the critical organ, a cumulative activity of 40 GBq of ¹⁷⁷Lu-PSMA I&T appears to be safe and justifiable. The correlation between pretherapeutic SUV and absorbed tumor dose emphasizes the need for PSMA-ligand PET imaging for patient selection.

Comparison of bone scintigraphy and 68Ga-PSMA PET for skeletal staging in prostate cancer

PURPOSE

The aim of our study was to compare the diagnostic performance of ⁶⁸Ga-PSMA PET and ^99mTc bone scintigraphy (BS) for the detection of bone metastases in prostate cancer (PC) patients.

METHODS

One hundred twenty-six patients who received planar BS and PSMA PET within three months and without change of therapy were extracted from our database. Bone lesions were categorized into benign, metastatic, or equivocal by two experienced observers. A best valuable comparator (BVC) was defined based on BS, PET, additional imaging, and follow-up data. The cohort was further divided into clinical subgroups (primary staging, biochemical recurrence, and metastatic castration-resistant prostate cancer [mCRPC]). Additionally, subgroups of patients with less than 30 days delay between the two imaging procedures and with additional single-photon emission computed tomography (SPECT) were analyzed.

RESULTS

A total of 75 of 126 patients were diagnosed with bone metastases. Sensitivities and specificities regarding overall bone involvement were 98.7-100 % and 88.2-100 % for PET, and 86.7-89.3 % and 60.8-96.1 % (p < 0.001) for BS, with ranges representing results for 'optimistic' or 'pessimistic' classification of equivocal lesions. Out of 1115 examined bone regions, 410 showed metastases. Region-based analysis revealed a sensitivity and specificity of 98.8-99.0 % and 98.9-100 % for PET, and 82.4-86.6 % and 91.6-97.9 % (p < 0.001) for BS, respectively. PSMA PET also performed better in all subgroups, except patient-based analysis in mCRPC.

CONCLUSION

Ga-PSMA PET outperforms planar BS for the detection of affected bone regions as well as determination of overall bone involvement in PC patients. Our results indicate that BS in patients who have received PSMA PET for staging only rarely offers additional information; however, prospective studies, including a standardized integrated x-ray computed tomography (SPECT/CT) protocol, should be performed in order to confirm the presented results.