EANM procedure guidelines for radionuclide therapy with 177Lu-labelled PSMA-ligands (177Lu-PSMA-RLT)

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

BACKGROUND

Individualized dosimetry is recommended for [¹⁷⁷Lu]Lu-PSMA radioligand therapy (RLT) which is resource-intensive and protocols are often not optimized. Therefore, a simulation study was performed focusing on the determination of efficient optimal sampling schedules (OSS) for renal and tumour dosimetry by investigating different numbers of time points (TPs).

METHODS

Sampling schedules with 1-4 TPs were investigated. Time-activity curves of the kidneys and two tumour lesions were generated based on a physiologically based pharmacokinetic (PBPK) model and biokinetic data of 13 patients who have undergone [¹⁷⁷Lu]Lu-PSMA I&T therapy. Systematic and stochastic noise of different ratios was considered when modelling time-activity data sets. Time-integrated activity coefficients (TIACs) were estimated by simulating the hybrid planar/SPECT method for schedules comprising at least two TPs. TIACs based on one single SPECT/CT measurement were estimated using an approximation for reducing the number of fitted parameters. For each sampling schedule, the root-mean-squared error (RMSE) of the deviations of the simulated TIACs from the ground truths for 1000 replications was used as a measure for accuracy and precision.

RESULTS

All determined OSS included a late measurement at 192 h p.i., which was necessary for accurate and precise tumour TIACs. OSS with three TPs were identified to be 3-4, 96-100 and 192 h with an additional SPECT/CT measurement at the penultimate TP. Kidney and tumour RMSE of 6.4 to 7.7% and 6.3 to 7.8% were obtained, respectively. Shortening the total time for dosimetry to e.g. 96 h resulted in kidney and tumour RMSE of 6.8 to 8.3% and 9.1 to 11%, respectively. OSS with four TPs showed similar results as with three TPs. Planar images at 4 and 68 h and a SPECT/CT shortly after the 68 h measurement led to kidney and tumour RMSE of 8.4 to 12% and 12 to 16%, respectively. One single SPECT/CT measurement at 52 h yielded good approximations for the kidney TIACs (RMSE of 7.0%), but led to biased tumour TIACs.

CONCLUSION

OSS allow improvements in accuracy and precision of renal and tumour dosimetry for [¹⁷⁷Lu]Lu-PSMA therapy with potentially less effort. A late TP is important regarding accurate tumour TIACs.

Nuclear medicine and molecular imaging advances in the 21st century

Currently, Nuclear Medicine has a clearly defined role in clinical practice due to its usefulness in many medical disciplines. It provides relevant diagnostic and therapeutic options leading to patients' healthcare and quality of life improvement. During the first two decades of the 21stt century, the number of Nuclear Medicine procedures increased considerably.Clinical and research advances in Nuclear Medicine and Molecular Imaging have been based on developments in radiopharmaceuticals and equipment, namely, the introduction of multimodality imaging. In addition, new therapeutic applications of radiopharmaceuticals, mainly in oncology, are underway.This review will focus on radiopharmaceuticals for positron emission tomography (PET), in particular, those labeled with Fluorine-18 and Gallium-68. Multimodality as a key player in clinical practice led to the development of new detector technology and combined efforts to improve resolution. The concept of dual probe (a single molecule labeled with a radionuclide for single photon emission computed tomography)/positron emission tomography and a light emitter for optical imaging) is gaining increasing acceptance, especially in minimally invasive radioguided surgery. The expansion of theranostics, using the same molecule for diagnosis (γ or positron emitter) and therapy (β minus or α emitter) is reshaping personalized medicine.Upcoming research and development efforts will lead to an even wider array of indications for Nuclear Medicine both in diagnosis and treatment.

[PSMA-based theranostics for prostate cancer : From imaging to treatment]

BACKGROUND

In recent years nuclear medicine theranostics using radiolabeled prostate-specific membrane antigen (PSMA) ligands have gained increasing importance in the management of prostate cancer.

AIM

The aim of this work is to highlight the value of theranostic concepts using radiolabeled PSMA ligands for both the diagnostic work-up and treatment of advanced prostate cancer.

MATERIAL AND METHODS

The currently available knowledge in the literature is summarized and presented.

RESULTS

The use of PSMA in positron emission tomography-computed tomography (PET/CT) shows a high sensitivity and specificity for prostate cancer imaging, particularly in patients with biochemical recurrences. Furthermore, promising results are also reported for staging of primary prostate cancer and treatment monitoring. In addition, radioligand therapy using alpha and beta emitters is a promising third line treatment option in intensively pretreated patients with metastases. The reduction of side effects and optimization of the treatment sequence of radioligand therapy is of increasing importance.

CONCLUSION

Nuclear medicine theranostics have an increasing clinical impact on the diagnostics and treatment of prostate cancer.

Neuron-specific enolase has potential value as a biomarker for [18F]FDG/[68Ga]Ga-PSMA-11 PET mismatch findings in advanced mCRPC patients

BACKGROUND

PSMA-targeted radioligand therapy (PSMA-RLT) yielded impressive results in the metastasized castration-resistant prostate carcinoma (mCRPC) setting. High expression of PSMA is essential for successful PSMA-RLT. However, some patients develop [18F]FDG-avid lesions with low or no PSMA expression ([18F]FDG/[68Ga]Ga-PSMA-11 mismatch findings on PET/CT) in the course of treatment. Those lesions are not affected by PSMA-RLT and a change in therapy management is needed. To enable early mismatch detection, possible blood parameters as indicators for the occurrence of [18F]FDG/[68Ga]Ga-PSMA-11 mismatch findings on PET/CT were evaluated.

METHODS

Retrospective study of N = 66 advanced mCRPC patients with dual [68Ga]Ga-PSMA-11 and [18F]FDG PET/CT imaging within 4 weeks, who were referred for or received [177Lu]Lu-PSMA-617 radioligand therapy. Prostate-specific antigen (PSA), neuron-specific enolase (NSE), gamma-glutamyltransferase (GGT), and alkaline phosphatase (ALP) were tested as indicators for the occurrence of [18F]FDG/[68Ga]Ga-PSMA-11 mismatch findings. Additional to absolute values, relative changes (ΔPSA, ΔNSE, ΔGGT, ΔALP) over a period of 4 ± 1 weeks prior to [18F]FDG PET/CT were analyzed.

RESULTS

In total, 41/66 (62%) patients revealed at least one [18F]FDG/[68Ga]Ga-PSMA-11 mismatch finding on PET/CT. These mismatch findings were detected in 13/41 (32%) patients by screening for and in 28/41 (68%) patients during PSMA-RLT. NSE serum level (55.4 ± 44.6 μg/l vs. 18.5 ± 8 μg/l, p < 0.001) and ΔNSE (93.8 ± 124.5% vs. 2.9 ± 39.5%, p < 0.001) were significantly higher in the mismatch group than in the non-mismatch group. No significant differences were found for serum PSA (p = 0.424), ΔPSA (p = 0.417), serum ALP (p = 0.937), ΔALP (p = 0.611), serum GGT (p = 0.773), and ΔGGT (p = 0.971). For NSE and ΔNSE, the maximum value of the Youden index in ROC analysis was at a cut-off level of 26.8 μg/l (sensitivity 78%, specificity 96%) and at + 13.9% (sensitivity 84%, specificity 75%), respectively. An introduced scoring system of both parameters achieved a sensitivity of 90% and a specificity of 88% for the occurrence of [18F]FDG/[68Ga]Ga-PSMA-11 mismatch.

CONCLUSION

We observed a significantly higher absolute serum concentration and a higher relative increase of NSE in advanced mCRPC patients with [18F]FDG-avid and insufficient PSMA expressing metastases ([18F]FDG/[68Ga]Ga-PSMA-11 mismatch findings on PET/CT) in our cohort. NSE might be used as a potential laboratory indicator for [18F]FDG/[68Ga]Ga-PSMA-11 mismatch findings, if this observation is confirmed in future, ideally prospective, studies in larger patient cohorts.

Prior therapies as prognostic factors of overall survival in metastatic castration-resistant prostate cancer patients treated with [177Lu]Lu-PSMA-617. A WARMTH multicenter study (the 617 trial)

Introduction

The impact of prior therapies, especially chemotherapy, on overall survival (OS) in patients with castration-resistant prostate cancer (CRPC) receiving [¹⁷⁷Lu]Lu-PSMA-617 therapy has been the subject of controversy. Therefore, WARMTH decided to plan a multicenter retrospective analysis (the “617 trial”) to evaluate response rate and OS as well as the impact of prior therapies on OS in more than 300 patients treated with ¹⁷⁷Lu-PSMA-617.

Materials and methods

The data of 631 metastatic CRPC (mCRPC) patients from 11 different clinics were evaluated. According to the inclusion and exclusion criteria, all patients had to have received at least abiraterone or enzalutamide prior to [¹⁷⁷Lu]Lu-PSMA-617 therapy. The patients were divided into three groups: patients who had received prior chemotherapy, patients who avoided chemotherapy, and patients for whom a chemotherapy was contraindicated.

Results

The analysis included the data of 416 patients, with a median age of 71.9 years. At the time of analysis, 87 patients (20,9%) were still alive. A total of 53.6% of patients had received both abiraterone and enzalutamide; 75.5% and 26.4% had a history of chemotherapy with docetaxel and cabazitaxel, respectively. A total of 20.4% had had Ra-223. The median OS was 11.1 months. Prior chemotherapy, the existence of bone and liver metastases, as well as Eastern Cooperative Oncology Group (ECOG) status, were significant prognosticators of worse overall survival in both univariate and multivariate analyses. Patients without any prior chemotherapy showed a significantly longer OS (14.6 months). The median OS in patients who received one or two lines of chemotherapy with docetaxel or docetaxel followed by cabazitaxel, respectively, was 10.9 months and 8.9 months. There was no difference in OS between patients who had not received chemotherapy and patients for whom chemotherapy was contraindicated. The other prior therapies did not have any significant impact on OS.

Conclusion

In the present multicenter analysis, chemotherapy-naïve mCRPC patients receiving [¹⁷⁷Lu]Lu-PSMA-617 therapy had a significantly longer OS than patients with a history of chemotherapy. This remained independent in the multivariate analysis besides presence of bone and liver metastases as negative prognosticators for survival, whereas an ECOG of 0–1 is associated with a longer OS.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-04797-9) contains supplementary material, which is available to authorized users.

Imaging DNA Damage Repair In Vivo After 177Lu-DOTATATE Therapy

Molecular radiotherapy using 177Lu-DOTATATE is a most effective treatment for somatostatin receptor-expressing neuroendocrine tumors. Despite its frequent and successful use in the clinic, little or no radiobiologic considerations are made at the time of treatment planning or delivery. On positive uptake on octreotide-based PET/SPECT imaging, treatment is usually administered as a standard dose and number of cycles without adjustment for peptide uptake, dosimetry, or radiobiologic and DNA damage effects in the tumor. Here, we visualized and quantified the extent of DNA damage response after 177Lu-DOTATATE therapy using SPECT imaging with 111In-anti-γH2AX-TAT. This work was a proof-of-principle study of this in vivo noninvasive biodosimeter with β-emitting therapeutic radiopharmaceuticals. Methods: Six cell lines were exposed to external-beam radiotherapy (EBRT) or 177Lu-DOTATATE, after which the number of γH2AX foci and the clonogenic survival were measured. Mice bearing CA20948 somatostatin receptor-positive tumor xenografts were treated with 177Lu-DOTATATE or sham-treated and coinjected with 111In-anti-γH2AX-TAT, 111In-IgG-TAT control, or vehicle. Results: Clonogenic survival after external-beam radiotherapy was cell-line-specific, indicating varying levels of intrinsic radiosensitivity. Regarding in vitro cell lines treated with 177Lu-DOTATATE, clonogenic survival decreased and γH2AX foci increased for cells expressing high levels of somatostatin receptor subtype 2. Ex vivo measurements revealed a partial correlation between 177Lu-DOTATATE uptake and γH2AX focus induction between different regions of CA20948 xenograft tumors, suggesting that different parts of the tumor may react differentially to 177Lu-DOTATATE irradiation. Conclusion:111In-anti-γH2AX-TAT allows monitoring of DNA damage after 177Lu-DOTATATE therapy and reveals heterogeneous damage responses.

177Lu-EB-PSMA Radioligand Therapy with Escalating Doses in Patients with Metastatic Castration-Resistant Prostate Cancer

This study was designed to assess the safety and therapeutic response to ¹⁷⁷Lu-labeled Evans blue-modified prostate-specific membrane antigen (PSMA) 617 (EB-PSMA-617) treatment with escalating doses in patients with metastatic castration-resistant prostate cancer. Methods: With institutional review board approval and informed consent, patients were randomly divided into 3 groups: group A (n = 10) was treated with a 1.18 ± 0.09 GBq dose of ¹⁷⁷Lu-EB-PSMA. Group B (n = 10) was treated with a 2.12 ± 0.19 GBq dose of ¹⁷⁷Lu-EB-PSMA. Group C (n = 8) was treated with a 3.52 ± 0.58 GBq dose of ¹⁷⁷Lu-EB-PSMA. Eligible patients received up to 3 cycles of ¹⁷⁷Lu-EB-PSMA therapy, at 8-wk intervals. Results: Because of disease progression or bone marrow suppression, 4 of 10, 5 of 10, and 5 of 8 patients completed 3 cycles of therapy as planned in groups A, B, and C, respectively. The prostate-specific antigen response was correlated with treatment dose, and the prostate-specific antigen disease control rates were higher in groups B (70%) and C (75%) than in group A (10%) (P = 0.007), but no correlation between groups B and C was found. ⁶⁸Ga-PSMA PET/CT showed a response in all treatment groups; however, there was no significant difference among the 3 groups. A hematologic toxicity study found that platelets decreased more in groups B and C than in group A and that grade 4 thrombocytopenia occurred in 2 (25.0%) patients in group C. No serious nephritic or hepatic side effects were observed. Conclusion: This study demonstrated that a 2.12-GBq dose of ¹⁷⁷Lu-EB-PSMA seems to be safe and adequate in tumor treatment. Further investigations with an increased number of patients are warranted.

Real-World Evidence of Clinical Outcomes in Precision Radionuclide Oncology: The NIGHTCAP Study of 177Lu-PSMA in Metastatic Prostate Cancer

A novel approach to current radiopharmaceutical study design to document the efficiency of 177Lu- PSMA-radioligand therapy of metastatic prostate cancer is described in a proposed prospective, real-time, realworld audit of a large patient population worldwide. The NIGHTCAP (National Investigators Global Harmonisation Theragnostics of Cancer of Prostate) Study will establish real-world evidence (RWE) of overall survival (OS) and quality of life (QoL) in patients undergoing routine 177Lu-PSMA-radioligand therapy on harmonised compassionate patient-usage protocols throughout the world. Such long-term efficiency data will be contrasted with the short-term randomised controlled trial (RCT) assessments of efficacy predicated upon surrogate markers of survival outcomes, such as progression-free survival (PFS). The shortcomings of RCT evaluation of the clinical benefit of new anticancer agents are detailed in this review, which advocates RWE to determine efficiency. The real-time monitoring of QoL in the NIGHTCAP Study is independent of questionnaires, language differences, or oncologist bias, and relies upon individual patient self-assessment by choice of one of five emoji which best reflects their mood each day.

(Radio)Theranostic Patient Management in Oncology Exemplified by Neuroendocrine Neoplasms, Prostate Cancer, and Breast Cancer

The role of nuclear medicine in the management of oncological patients has expanded during last two decades. The number of radiopharmaceuticals contributing to the realization of theranostics/radiotheranostics in the context of personalized medicine is increasing. This review is focused on the examples of targeted (radio)pharmaceuticals for the imaging and therapy of neuroendocrine neoplasms (NENs), prostate cancer, and breast cancer. These examples strongly demonstrate the tendency of nuclear medicine development towards personalized medicine.

Digital Solid-State SPECT/CT Quantitation of Absolute 177Lu Radiotracer Concentration: In Vivo and In Vitro Validation

The accuracy of ¹⁷⁷Lu radiotracer concentration measurements using quantitative clinical software was determined by comparing in vivo results for a digital solid-state cadmium-zinc-telluride SPECT/CT system with in vitro sampling. Methods: First, image acquisition parameters were assessed for an International Electrotechnical Commission body phantom emulating clinical count rates loaded with a lung insert and 6 hot spheres with a 12:1 target-to-background ratio of ¹⁷⁷Lu solution. Then, the data of 28 whole-body SPECT/CT scans of 7 patients who underwent ¹⁷⁷Lu prostate-specific membrane antigen radioligand therapy were retrospectively analyzed. Three users analyzed SPECT/CT images for in vivo urinary bladder radiotracer uptake using quantitative software. In vitro radiopharmaceutical concentrations were calculated using urine sampling obtained immediately after each scan, scaled to SUVs. Any in vivo or in vitro identity relations were determined by linear regression (ideally, slope = 1 and intercept = 0), within a 95% confidence interval. Results: Phantom results demonstrated lower quantitative error for acquisitions using the 113-keV ¹⁷⁷Lu energy peak rather than including the 208-keV peak, given that only low-energy collimation was available in this camera configuration. In the clinical study, 24 in vivo-in vitro pairs were eligible for further analysis, with 4 having been rejected as outliers (via Cook distance calculations). All linear regressions (R ² ≥ 0.82, P < 0.0001) provided identity in vivo-in vitro relations (95% confidence interval), with SUV averages from all users giving a slope of 0.96 ± 0.13, an intercept of -0.07 ± 0.46 g/mL, and an average residual difference of 19.5%. In acquisitions with the lower-energy ¹⁷⁷Lu energy peak, solid-state SPECT/CT imaging provided an accuracy to within approximately 20% of in vivo urinary bladder radiotracer concentrations. Conclusion: This noninvasive in vivo quantitation method can potentially improve diagnosis, patient management, and treatment response assessment and provide data essential to ¹⁷⁷Lu dosimetry.

Interobserver agreement of [68Ga]Ga-PSMA-11 PET/CT images interpretation in men with newly diagnosed prostate cancer

Background

Prostate-specific membrane antigen (PSMA) ligand PET/CT has already provided promising results in prostate cancer (PC) imaging, yet simple and reproductible reporting criteria are still lacking. This study aimed at retrospectively evaluating interobserver agreement of [⁶⁸Ga]Ga-PSMA-11 PET/CT images interpretation according to PC molecular imaging standardized evaluation (PROMISE) criteria and reproducibility of PSMA reporting and data systems (RADS).

Methods

Forty-three patients with newly diagnosed, histologically proven intermediate- or high-risk PC, eligible for radical prostatectomy and who underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT before surgery were retrospectively included. Three nuclear medicine physicians (2 experienced and 1 resident) independently reviewed PET/CT images. Interpretation of [⁶⁸Ga]Ga-PSMA-11 PET/CT images was based on PROMISE criteria including miTNM staging and lesions miPSMA expression score visual estimation and PSMA-RADS version 1.0 for a given scan. Readers’ agreement was measured using Krippendorff’s coefficients

Results

Agreement between observers was almost perfect (coefficient ≥ 0.81) for miM; it was substantial (coefficient ≥ 0.61) for the following criteria: miT, miN, PSMA-RADS, and miPSMA expression score of primary PC lesion and metastases. However, agreement was moderate (coefficient = 0.41–0.60) for miPSMA score of positive lymph nodes and for detection of PC primary lesion.

Conclusion

Visual interpretation of [⁶⁸Ga]Ga-PSMA-11 PET/CT images in patients with newly diagnosed PC in a clinical setting leads to at least substantial agreement for PROMISE criteria and PSMA-RADS classification except for PC primary lesion detection and for miPSMA expression scoring of positive lymph nodes that might have been hampered by the interindividual variability of reference organs PSMA expression.

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.

A Step-by-Step Guide for the Novel Radiometal Production for Medical Applications: Case Studies with 68Ga, 44Sc, 177Lu and 161Tb

The production of novel radionuclides is the first step towards the development of new effective radiopharmaceuticals, and the quality thereof directly affects the preclinical and clinical phases. In this review, novel radiometal production for medical applications is briefly elucidated. The production status of the imaging nuclide 44Sc and the therapeutic β--emitter nuclide 161Tb are compared to their more established counterparts, 68Ga and 177Lu according to their targetry, irradiation process, radiochemistry, and quality control aspects. The detailed discussion of these significant issues will help towards the future introduction of these promising radionuclides into drug manufacture for clinical application under Good Manufacturing Practice (GMP).

225Ac-PSMA-617 for Therapy of Prostate Cancer

Prostate-specific membrane antigen (PSMA)-targeting radio-ligand therapy with beta-emitting ¹⁷⁷Lutetium has already been investigated in several early phase dosimetry studies, demonstrated promising results in phase-2, and recently the first phase-3 trial finished recruitment. In contrast, PSMA-targeting alpha-particle therapy (TAT) has only been evaluated in few preclinical experiments, preliminary dosimetry attempts and some retrospective observational studies, yet. First clinical experience with ²²⁵Ac-PSMA-617 demonstrates promising antitumor activity with a 63%-70% PSA_>50%-response rate, 10-15 months duration of response and complete remissions in approximately ten percent of patients, some of them with enduring relapse-free survival. Nevertheless, without comparative trials there is no prove whether, applied in identical clinical situations, ²²⁵Ac-PSMA-617 is really more efficiently than ¹⁷⁷Lu-PSMA-617 or vice versa. However, there is some good rationale, that PSMA-TAT might have advantages in particular clinical indications. This includes patients with diffuse type red-marrow infiltration by reducing off-target radiation to surrounding cells; ablation of micrometastases after favorable response to other previous therapy or someday in early stage disease. Also treatment escalation of patients, either with poor response to ¹⁷⁷Lu-PSMA or harboring adverse prognostic biomarkers, appears promising. In preclinical research, alpha-radiation demonstrated stronger induction of abscopal effects than beta-radiation; favoring its usage as a combination partner with immunotherapies. So, further evaluation of PSMA-TAT is definitely warranted. Recently, de-escalated treatment protocols and application of ²²⁵Ac/¹⁷⁷Lu-PSMA "cocktail"-regimens improved the tolerability of ²²⁵Ac-PSMA-617 TAT, reducing the risk for development dry-mouth syndrome. This opens new avenues for future application in earlier stage disease.

Theragnostic Use of Radiolabelled Dota-Peptides in Meningioma: From Clinical Demand to Future Applications

Meningiomas account for approximately 30% of all new diagnoses of intracranial masses. The 2016 World Health Organization's (WHO) classification currently represents the clinical standard for meningioma's grading and prognostic stratification. However, watchful waiting is frequently the chosen treatment option, although this means the absence of a certain histological diagnosis. Consequently, MRI (or less frequently CT) brain imaging currently represents the unique available tool to define diagnosis, grading, and treatment planning in many cases. Nonetheless, these neuroimaging modalities show some limitations, particularly in the evaluation of skull base lesions. The emerging evidence supporting the use of radiolabelled somatostatin receptor analogues (such as dota-peptides) to provide molecular imaging of meningiomas might at least partially overcome these limitations. Moreover, their potential therapeutic usage might enrich the current clinical offering for these patients. Starting from the strengths and weaknesses of structural and functional neuroimaging in meningiomas, in the present article we systematically reviewed the published studies regarding the use of radiolabelled dota-peptides in surgery and radiotherapy planning, in the restaging of treated patients, as well as in peptide-receptor radionuclide therapy of meningioma.