How to design a theranostic trial?

The field of nuclear theranostic clinical trials is continuously expanding as an increasing number of novel agents and treatment combinations are explored for treating advanced and metastatic cancers. Moving from 'bench-to-bedside' is oftentimes a complex and lengthy process. The objective of this overview is to explore the basic elements involved in designing clinical trials with a special focus on theranostics in nuclear medicine. The 'bench-to-bedside' journey involves translating basic scientific research into patient-effective treatments. Preclinical studies, a crucial initial step, are a complex process encompassing in vitro experiments, in vivo studies, and animal models to explore hypotheses in humans. Clinical trials follow, with predefined phases assessing safety, effectiveness, and comparisons to existing treatments. This process demands investments in data management, statistics, good clinical practice (GCP) accreditations, and collaborative efforts for funding and sustainable pricing. Theranostics, merging diagnostics and personalized treatment, is at the forefront. Continuous efforts to enhance existing agents involve reducing adverse effects, exploring new indications, and incorporating advanced imaging modalities. Radionuclide therapy, unique with non-uniform distribution and complex radiobiology, plays a distinct role. This article explores trends and challenges in each clinical trial phase in light of the emerging field of theranostics in nuclear medicine, emphasizing meticulous trial design, dosimetry optimization, and the necessity of collaborative stakeholder efforts for successful implementation.

Reduction of [68Ga]Ga-DOTA-TATE injected activity for digital PET/MR in comparison with analogue PET/CT.

BACKGROUND: New digital detectors and block-sequential regularized expectation maximization (BSREM) reconstruction algorithm improve positron emission tomography (PET)/magnetic resonance (MR) image quality. The impact on image quality may differ from analogue PET/computed tomography (CT) protocol. The aim of this study is to determine the potential reduction of injected [68Ga]Ga-DOTA-TATE activity for digital PET/MR with BSREM reconstruction while maintaining at least equal image quality compared to the current analogue PET/CT protocol. METHODS: NEMA IQ phantom data and 25 patients scheduled for a diagnostic PET/MR were included. According to our current protocol, 1.5 MBq [68Ga]Ga-DOTA-TATE per kilogram (kg) was injected. After 60 min, scans were acquired with 3 (≤ 70 kg) or 4 (> 70 kg) minutes per bedposition. PET/MR scans were reconstructed using BSREM and factors ß 150, 300, 450 and 600. List mode data with reduced counts were reconstructed to simulate scans with 17%, 33%, 50% and 67% activity reduction. Image quality was measured quantitatively for PET/CT and PET/MR phantom and patient data. Experienced nuclear medicine physicians performed visual image quality scoring and lesion counting in the PET/MR patient data. RESULTS: Phantom analysis resulted in a possible injected activity reduction of 50% with factor ß = 600. Quantitative analysis of patient images revealed a possible injected activity reduction of 67% with factor ß = 600. Both with equal or improved image quality as compared to PET/CT. However, based on visual scoring a maximum activity reduction of 33% with factor ß = 450 was acceptable, which was further limited by lesion detectability analysis to an injected activity reduction of 17% with factor ß = 450. CONCLUSION: A digital [68Ga]Ga-DOTA-TATE PET/MR together with BSREM using factor ß = 450 result in 17% injected activity reduction with quantitative values at least similar to analogue PET/CT, without compromising on PET/MR visual image quality and lesion detectability.

Implementing Ac-225 labelled radiopharmaceuticals: practical considerations and (pre-)clinical perspectives.

BACKGROUND: In the past years, there has been a notable increase in interest regarding targeted alpha therapy using Ac-225, driven by the observed promising clinical anti-tumor effects. As the production and technology has advanced, the availability of Ac-225 is expected to increase in the near future, making the treatment available to patients worldwide. MAIN BODY: Ac-225 can be labelled to different biological vectors, whereby the success of developing a radiopharmaceutical depends heavily on the labelling conditions, purity of the radionuclide source, chelator, and type of quenchers used to avoid radiolysis. Multiple (methodological) challenges need to be overcome when working with Ac-225; as alpha-emission detection is time consuming and highly geometry dependent, a gamma co-emission is used, but has to be in equilibrium with the mother-nuclide. Because of the high impact of alpha emitters in vivo it is highly recommended to cross-calibrate the Ac-225 measurements for used quality control (QC) techniques (radio-TLC, HPLC, HP-Ge detector, and gamma counter). More strict health physics regulations apply, as Ac-225 has a high toxicity, thereby limiting practical handling and quantities used for QC analysis. CONCLUSION: This overview focuses specifically on the practical and methodological challenges when working with Ac-225 labelled radiopharmaceuticals, and underlines the required infrastructure and (detection) methods for the (pre-)clinical application.

Evaluation of the tolerability and safety of [225Ac]Ac-PSMA-I&T in patients with metastatic prostate cancer: a phase I dose escalation study.

BACKGROUND: Life expectancy of patients with metastatic castration-resistant prostate cancer (mCRPC) is still limited despite several systemic treatments. Within five years after diagnosis of primary prostate cancer, 10-20% of the patients have mCRPC and curation is not an option. Radionuclide therapy (RNT) targeted against prostate-specific membrane antigen (PSMA) emerged as a new treatment option and showed effective results in patients with mCRPC. Survival benefit after [177Lu]Lu-PSMA RNT has already been demonstrated in several clinical trials. However, [225Ac]Ac-PSMA (225Ac-PSMA) appears to be an even more promising radiopharmaceutical for the treatment of mCRPC. The use of alpha emitting radionuclides offers advantages over beta emitting radionuclides due to the high linear energy transfer effective for killing tumor cells and the limited range to reduce the radiation effects on the healthy tissue. However, these results are based on retrospective data and safety data of 225Ac-PSMA are still limited. Therefore, a prospective trial is needed to determine the optimal amount of activity that can be administered. METHODS: The 225Ac-PSMA-Imaging & Therapy (I&T) trial is an investigator-initiated phase I, single-center, open label, repeated dose-escalation and expansion trial. Patient with PSMA-positive mCRPC after at least one line of chemotherapy and/or one line of nonsteroidal antiandrogen will be treated with 225Ac-PSMA-I&T in increasing amount of activity per cycle. Dose-escalation following an accelerated 3 + 3 design which allows to open the next dose-level cohort in the absence of dose limiting toxicity while the previous one is still ongoing. Up to 4 treatment cohorts will be explored including up to 3 dose-escalation cohorts and one expansion cohort where patients will be administered with the recommended dose. A total of up to 30 patients will be enrolled in this trial. All patients will be evaluated for safety. Additionally, dosimetry was performed for the patients in the dose-escalation cohorts after the first 225Ac-PSMA-I&T administration. DISCUSSION: This trial will assess the safety and tolerability of 225Ac-PSMA-I&T in patients with mCRPC to recommend the optimal dose for the phase II trial. TRIAL REGISTRATION: ClinicalTrials.gov, (NCT05902247). Retrospectively registered 13 June 2023.

68Ga-PSMA PET/CT for Response Evaluation of 223Ra Treatment in Metastatic Prostate Cancer.

CT and bone scintigraphy are not useful for response evaluation of bone metastases to 223Ra treatment in metastatic castration-resistant prostate cancer (mCRPC). PET using 68Ga prostate-specific membrane antigen 11 (68Ga-PSMA) is a promising tool for response evaluation of mCRPC. The aim of this study was to determine the utility of 68Ga-PSMA PET/CT for response evaluation of 223Ra treatment in patients with mCRPC. Methods: Within this prospective, multicenter, imaging discovery study, 28 patients with mCRPC, eligible for 223Ra treatment, were included between 2019 and 2022. Patients received 223Ra according to the standard of care. Study procedures included CT, bone scintigraphy, and 68Ga-PSMA PET/CT at baseline, after 3 and 6 cycles of 223Ra treatment, and on treatment failure. Response to 223Ra treatment was visually assessed on all 3 imaging modalities. Total tumor volume within bone (TTVbone) was determined on 68Ga-PSMA PET/CT. Intrapatient heterogeneity in response was studied using a newly developed image-registration tool for sequential images of PET/CT. Results were compared with failure-free survival (good responders vs. poor responders; cutoff, 24 wk) and alkaline phosphatase (ALP) response after 3 cycles. Results: Visual response assessment criteria could not distinguish good responders from poor responders on 68Ga-PSMA PET/CT and bone scintigraphy. For 68Ga-PSMA PET/CT, TTVbone at baseline was lower in good responders than in poor responders, whereas TTVbone increased in both groups during treatment. TTVbone was higher in patients with new extraosseous metastases during 223Ra treatment. Although TTVbone and ALP correlated at baseline, changes in TTVbone and ALP on treatment did not. 68Ga-PSMA response of TTVbone showed intrapatient heterogeneity in most patients. Conclusion: mCRPC patients with lower TTVbone on 68Ga-PSMA PET/CT have the best clinical outcome after 223Ra treatment. Response is highly heterogeneous in most patients. A decrease in ALP, which occurred in most patients, was not correlated with a decrease in TTVbone, which might make one question the value of ALP for disease monitoring during 223Ra treatment in clinical practice.

Long-Term Outcomes of Submaximal Activities of Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE in Neuroendocrine Tumor Patients.

In the literature, up to 45% of neuroendocrine tumor (NET) patients who are treated with 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) do not receive the intended cumulative activity of 29.6 GBq (800 mCi). The aim of this study was to analyze the efficacy of submaximal activities of PRRT in patients who discontinued treatment for non-disease-related reasons. Methods: We retrospectively included patients with well-differentiated and advanced NETs who underwent PRRT from 2000 until 2019 and did not receive 29.6 GBq of 177Lu-DOTATATE. For comparison, we selected control NET patients who received the intended cumulative activity of 29.6 GBq of 177Lu-DOTATATE between 2000 and 2012. Primary outcomes were progression-free survival (PFS) and tumor response, and the secondary outcome was overall survival (OS). Results: In total, 243 patients received 3.7-27.8 GBq. In 130 patients, the submaximal activity was unrelated to disease (e.g., bone marrow and renal toxicity in 48% and maximal renal absorbed dose in 23%), and they were included. Patients receiving a reduced activity had more bone metastases, a lower body mass index and albumin level, a higher alkaline phosphatase level, and fewer grade 1 tumors than the 350 patients included in the control group. The disease control rate in the reduced-activity group was 85%, compared with 93% for the control group (P = 0.011). The median PFS (95% CI) was 23 mo (range, 21-26 mo) for the reduced-activity group and 31 mo (range, 27-35 mo) for the control group (P = 0.001), and the median OS (95% CI) was 34 mo (range, 28-40 mo) and 60 mo (range, 53-67 mo), respectively (P < 0.0001). With adjustment for relevant confounders in the multivariable Cox regression analyses, cumulative activity was an independent predictor of both PFS and OS. Conclusion: In NET patients treated with a cumulative activity of less than 29.6 GBq of 177Lu-DOTATATE, PRRT was less efficacious in tumor response and survival than in patients who received 29.6 GBq.

Efficacy and safety of peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE in 15 patients with progressive treatment-refractory meningioma.

PURPOSE: There is no evidence-based systemic therapy for patients with progressive meningiomas for whom surgery or external radiotherapy is no longer an option. In this study, the efficacy and safety of peptide receptor radionuclide therapy (PRRT) in patients with progressive, treatment-refractory meningiomas were evaluated. METHODS: Retrospective analysis of all meningioma patients treated with [177Lu]Lu-DOTA-TATE from 2000 to 2020 in our centre. Primary outcomes were response according to RANO bidimensional and volumetric criteria and progression-free survival (PFS). Overall survival (OS) and tumour growth rate (TGR) were secondary endpoints. TGR was calculated as the percentage change in surface or volume per month. RESULTS: Fifteen meningioma patients received [177Lu]Lu-DOTA-TATE (7.5-29.6 GBq). Prior to PRRT, all patients had received external radiotherapy, and 14 patients had undergone surgery. All WHO grades were included WHO 1 (n=3), WHO 2 (n=5), and WHO 3 (n=6). After PRRT, stable disease was observed in six (40%) patients. The median PFS was 7.8 months with a 6-month PFS rate of 60%. The median OS was 13.6 months with a 12-month OS rate of 60%. All patients had progressive disease prior to PRRT, with an average TGR of 4.6% increase in surface and 14.8% increase in volume per month. After PRRT, TGR declined to 3.1% in surface (p=0.016) and 5.0% in volume (p=0.013) per month. CONCLUSION: In this cohort of meningioma patients with exhaustion of surgical and radiotherapeutic options and progressive disease, it was shown that PRRT plays a role in controlling tumour growth.

A Clinical Guide to Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE in Neuroendocrine Tumor Patients.

Peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-[DOTA0,Tyr3]-octreotate (177Lu-DOTATATE) has become an established second- or third-line treatment option for patients with somatostatin receptor (SSTR)-positive advanced well-differentiated gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). Clinical evidence of the efficacy of PRRT in tumor control has been proven and lower risks of disease progression or death are seen combined with an improved quality of life. When appropriate patient selection is performed, PRRT is accompanied by limited risks for renal and hematological toxicities. Treatment of NET patients with PRRT requires dedicated clinical expertise due to the biological characteristics of PRRT and specific characteristics of NET patients. This review provides an overview for clinicians dealing with NET on the history, molecular characteristics, efficacy, toxicity and relevant clinical specifics of PRRT.

Peptide Receptor Radionuclide Therapy.

The concept of using a targeting molecule labeled with a diagnostic radionuclide for using positron emission tomography or single photon emission computed tomography imaging with the potential to demonstrate that tumoricidal radiation can be delivered to tumoral sites by administration of the same or a similar targeting molecule labeled with a therapeutic radionuclide termed "theranostics." Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs (SSAs) is a well-established second/third-line theranostic treatment for somatostatin receptor-positive well-differentiated (neuro-)endocrine neoplasms (NENs). PRRT with 177Lu-DOTATATE was approved by the regulatory authorities in 2017 and 2018 for selected patients with low-grade well-differentiated gastroenteropancreatic (GEP) NENs. It improves progression-free survival as well as quality of life of GEP NEN patients. Favorable symptomatic and biochemical responses using PRRT with 177Lu-DOTATATE have also been reported in patients with functioning metastatic GEP NENs like metastatic insulinomas, Verner Morrison syndromes (VIPomas), glucagonomas, and gastrinomas and patients with carcinoid syndrome. This therapy might also become a valuable therapeutic option for inoperable low-grade bronchopulmonary NENs, inoperable or progressive pheochromocytomas and paragangliomas, and medullary thyroid carcinomas. First-line PRRT with 177Lu-DOTATATE and combinations of this therapy with cytotoxic drugs are currently under investigation. New radiolabeled somatostatin receptor ligands include SSAs coupled with alpha radiation emitting radionuclides and somatostatin receptor antagonists coupled with radionuclides.

Advances in 177Lu-PSMA and 225Ac-PSMA Radionuclide Therapy for Metastatic Castration-Resistant Prostate Cancer.

For patients with metastatic castration-resistant prostate cancer (mCRPC), the survival benefit of classic treatment options with chemotherapy and drugs targeting androgen signaling is limited. Therefore, beta and alpha radionuclide therapy (RNT) have emerged as novel treatment options for patients with mCRPC. Radioligands target the prostate-specific membrane antigen (PSMA) epitopes, which are upregulated up to a thousand times more in prostate cancer cells compared to the cells in normal tissues. For this reason, PSMA is an excellent target for both imaging and therapy. Over the past years, many studies have investigated the treatment effects of lutetium-177 labeled PSMA (177Lu-PSMA) and actinium-225 labeled PSMA (225Ac-PSMA) RNT in patients with mCRPC. While promising results have been achieved, this field is still in development. In this review, we have summarized and discussed the clinical data of 177Lu-PSMA and 225Ac-PSMA RNT in patients with mCRPC.

Comparison of [18F]DOPA and [68Ga]DOTA-TOC as a PET imaging tracer before peptide receptor radionuclide therapy.

BACKGROUND: In treatment of neuroendocrine neoplasms (NENs), confirmation of somatostatin receptor expression with 68Ga-DOTA somatostatin analogues is mandatory to determine eligibility for peptide receptor radionuclide therapy (PRRT). [18F]DOPA can detect additional lesions compared to [68Ga]DOTA-TOC. The aim of this study was to explore differences in tumour detection of both tracers and their relevance for selecting patients for PRRT. We retrospectively studied eight patients with NENs who underwent both [68Ga]DOTA-TOC and carbidopa-enhanced [18F]DOPA PET/CT, before first-time PRRT with [177Lu]DOTA-TATE. Tracer order was influenced due to stock availability or to detect suspected metastases with a second tracer. On CT, disease control was defined as a lesion showing complete response, partial response, or stable disease, according to RECIST 1.1. RESULTS: Seven patients with in total 89 lesions completed four infusions of 7.4 GBq [177Lu]DOTA-TATE, one patient received only two cycles. Before treatment, [18F]DOPA PET/CT detected significantly more lesions than [68Ga]DOTA-TOC PET/CT (79 vs. 62, p < .001). After treatment, no difference in number of lesions with disease control was found for [18F]DOPA-only (5/27) and [68Ga]DOTA-TOC-only lesions (4/10, p = .25). [18F]DOPA detected more liver metastases (24/27) compared to [68Ga]DOTA-TOC (7/10, p = .006). Six patients showed inpatient heterogeneity in treatment response between [18F]DOPA-only and [68Ga]DOTA-TOC-only lesions. CONCLUSIONS: Response to PRRT with [177Lu]DOTA-TATE was comparable for both [68Ga]DOTA-TOC- and [18F]DOPA-only NEN lesions. [18F]DOPA may be capable of predicting response to PRRT while finding more lesions compared to [68Ga]DOTA-TOC, although these additional lesions are often small of size and undetected by diagnostic CT.

Prognostic value of dysnatremia for survival in neuroendocrine neoplasm patients.

Objective: Hyponatremia and hypernatremia are common electrolyte abnormalities in patients with malignancy and have been independently associated with worse survival outcomes. To date, there are no data on the impact of dysnatremia on survival outcomes in patients with neuroendocrine neoplasms (NENs). Design: This study involves retrospective cohort analysis from a tertiary care center of NEN patients treated with peptide receptor radionuclide therapy (PRRT) with a cumulative activity of at least 3.7 GBq 177Lu-DOTATATE between the years 2000 and 2015. Methods: Comparison of overall survival of patients with the occurrence of hyponatremia (serum sodium < 135 mmol/L) or hypernatremia (serum sodium > 145 mmol/L) before starting or during PRRT was perfomed. Results: A total of 649 patients were included. Hyponatremia occurred in 57 patients during the observation period and was associated with a shorter median overall survival (95% CI) of 25 months (14-36) compared to 55 months (48-61) of the 512 normonatremic patients (P < 0.001), adjusted hazard ratio (HR): 1.48 (95% CI: 1.04-2.12). Overall survival time was reduced regardless of whether hyponatremia was present at baseline or during PRRT. In contrast, hypernatremia occurred in 80 patients and was associated with a longer median overall survival (95% CI) of 94 months (47-140) compared with the 512 normonatremic patients (P = 0.018), adjusted HR: 0.61 (95% CI: 0.40-0.92). This association was driven by the patients with hypernatremia during PRRT. No association between dysnatremia and progression-free survival after PRRT was observed. Conclusions: The occurrence of hypo- or hypernatremia in PRRT-treated NET patients is associated with opposing outcomes with regard to overall survival. Sodium levels might have a prognostic role in these patients.

Dose-Limiting Bone Marrow Toxicities After Peptide Receptor Radionuclide Therapy Are More Prevalent in Women Than in Men.

PURPOSE: Peptide receptor radionuclide therapy (PRRT) can cause dose-limiting toxicities (DLTs) of the bone marrow, liver, and kidneys. It is yet unknown whether women and men are equally at risk of these DLTs. METHODS: Neuroendocrine tumor patients treated with 177Lu-DOTATATE between 2000 and 2015 in our phase II trial with available laboratory data were included. For all DLTs, the highest Common Terminology Criteria for Adverse Events (version 4.03) grades that occurred from the start of PRRT until 3 months after the last cycle were scored. RESULTS: At baseline, women (n = 439) had a significantly lower body mass index, Karnofsky Performance Score, hemoglobin level, and creatinine clearance and a significantly higher platelet level than men (n = 534). Both groups received a median activity of 29.6 GBq (800 mCi). After the start of PRRT, women more frequently developed grade ≥2 thrombocytopenia compared with men (25% vs 18%, P = 0.004) due to a significant increase in grade ≥3 thrombocytopenia (11% vs 6%, P = 0.008). Furthermore, the incidence of grade ≥3 anemia was higher in women (7% vs 3%, P = 0.002). In the multivariable regression model, female sex (odds ratio, 2.50; 95% confidence interval, 1.67-3.74) was confirmed to be an independent risk factor for grade ≥2 thrombocytopenia, among baseline platelet count, bone metastases, uptake on 111In-DTPA-octreotide scan, Karnofsky Performance Score, alkaline phosphatase, lymphocytes, albumin, and renal function. CONCLUSIONS: Female neuroendocrine tumor patients more often experienced PRRT-induced toxicities of platelets and hemoglobin than males, but this did not lead to a lower cumulative activity.

Induction therapy with 177Lu-DOTATATE procures long-term survival in locally advanced or oligometastatic pancreatic neuroendocrine neoplasm patients.

PURPOSE: Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE induces objective response in up to 57% of pancreatic neuroendocrine neoplasms (panNENs). Therefore, PRRT may comprise a downstaging option for panNEN patients who are not eligible for upfront curative surgery or are at high risk for recurrence. The aim of this study was to assess the potency of induction PRRT for locally advanced panNENs and to evaluate the effect of surgery after PRRT on overall survival (OS). METHODS: Retrospective cohort study of panNEN patients treated with induction 177Lu-DOTATATE. RESULTS: After PRRT, 26 out of 49 patients underwent pancreatic surgery with curative intent (PRRT + surgery). Partial objective response was obtained in 62% of the PRRT + surgery group versus 26% of the patients not undergoing panNEN surgery (PRRT-only group, p = 0.02). Downstaging in tumour-vessel interface was observed in 38% of all patients with at least one involved vessel. Median OS was 14.7 years (95% CI 5.9-23.6) for the PRRT + surgery group compared to 5.5 years (95% CI 4.5-6.5) for the PRRT-only group (p = 0.003). In the Cox proportional hazards analysis, surgery was not significantly associated with OS after propensity score adjustment with cumulative activity, performance status, tumour size after PRRT, and tumour grade. Median progression-free survival was 5.3 years (95% CI 2.4-8.1) for the PRRT + surgery group and 3.0 years (95% CI 1.6-4.4) for the PRRT-only group (p = 0.02). CONCLUSION: Early administration of PRRT followed by surgery is associated with favourable long-term outcomes in patients with locally advanced or oligometastatic panNEN and can be considered for selected patients with vascular involvement and/or increased risk of recurrence.

Inflammatory markers and long term hematotoxicity of holmium-166-radioembolization in liver-dominant metastatic neuroendocrine tumors after initial peptide receptor radionuclide therapy.

PURPOSE: In patients with neuroendocrine tumor liver metastases, additional tumor reduction can be achieved by sequential treatment with [166Ho]-radioembolization after peptide receptor radionuclide therapy (PRRT). The aim of this study was to analyze hematotoxicity profiles, (i.e. lymphocyte and neutrophile toxicity) and the prognostic value of neutrophil-to-lymphocyte ratio (NLR) and thrombocyte-to-lymphocyte ratio (TLR). METHODS: All patients included in the prospective HEPAR PLuS study were included in this study. Blood testing was performed at baseline (before radioembolization) and at regular intervals during 1-year follow-up. Radiological response was assessed at 3, 6, 9, and 12 months according to RECIST 1.1. Logistic regression was used to analyze the prognostic value of NLR and TLR on response. RESULTS: Thirty-one patients were included in the toxicity analysis; thirty were included in the response analysis. Three weeks after radioembolization, a significant decrease in lymphocyte count (mean change - 0.26 × 109/L) was observed. Ten patients (32.2%) experienced grade 3-4 lymphocyte toxicity. This normalized at 6 weeks and 3 months after treatment, while after 6 months a significant increase in lymphocyte count was observed. An increase in NLR and TLR at 3 weeks, compared to baseline, significantly predicted response at 3 months (AUC = 0.841 and AUC = 0.839, respectively) and at 6 months (AUC = 0.779 and AUC = 0.765). No significant relation with survival was found. CONCLUSIONS: Toxicity after sequential treatment with PRRT and [166Ho]-radioembolization is limited and temporary, while significant additional benefit can be expected. Change in NLR and TLR at 3-weeks follow-up may be valuable early predictors of response. Trial registration ClinicalTrials.gov, NCT02067988. Registered 20 February 2014, https://clinicaltrials.gov/ct2/show/record/NCT02067988 .

Prognostic significance of hyperammonemia in neuroendocrine neoplasm patients with liver metastases.

Neuroendocrine neoplasms (NENs) are rare, usually slow-growing tumors, often presenting with extensive liver metastases. Hyperammonemia due to insufficient hepatic clearance has been described in NEN cases; however, no systematic evaluation of risk factors and outcomes of NEN-associated hyperammonemia exists so far. This case report and retrospective review of NEN patients developing hyperammonemia from the years 2000 to 2020 at the Erasmus Medical Center in Rotterdam, the Netherlands, aimed to describe these patients and determine prognostic factors to improve evaluation and treatment. Forty-four NEN patients with documented hyperammonemia were identified. All patients had liver metastases with 30% (n = 13) showing signs of portal hypertension. Patients who developed encephalopathy had higher median ammonia levels, but there was no association between the severity of hyperammonemia and liver tumor burden or presence of liver insufficiency. Eighty-four percent (n = 37) of patients died during follow-up. The median (IQR) time from diagnosis of hyperammonemia to death was 1.7 months (0.1-22.7). Hyperbilirubinemia, hypoalbuminemia, elevated international normalized ratio, presence of liver insufficiency, encephalopathy and ascites were associated with worse outcomes. Their role as independent risk factors for mortality was confirmed using the Child-Pugh score as a summary factor (P < 0.001). No difference was seen concerning overall survival between our hyperammonemia patients and a propensity score-matched control stage IV NEN cohort. In conclusion, hyperammonemia comprises a relevant and potentially underdiagnosed complication of NEN liver metastases and is associated with worse outcomes. Assessment of signs of encephalopathy, risk factors and the Child-Pugh score could be helpful in selecting patients in whom ammonia levels should be measured.

Matching-adjusted indirect treatment comparison of [177Lu]Lu-DOTA-TATE, everolimus and sunitinib in advanced, unresectable gastroenteropancreatic neuroendocrine tumours: Relative effectiveness of [177Lu]Lu-DOTA-TATE in gastroenteropancreatic neuroendocrine tumours.

Head-to-head comparisons of the efficacy of treatments for gastroenteropancreatic neuroendocrine tumours (GEP-NETs) have not yet been reported. This study used a series of matching-adjusted indirect comparisons to indirectly compare the effectiveness of [177Lu]Lu-DOTA-TATE to everolimus, sunitinib and best supportive care (BSC) for extending progression-free survival and overall survival in patients with advanced, unresectable gastrointestinal (GI)-NETs and P-NETs. The results of the main analysis suggest that after accounting for differences in key prognostic variables, the hazard of progression was 62% (hazard ratio [HR], 0.38; confidence interval [CI]95 0.25-0.58) and 65% (HR 0.35 CI95 0.21-0.59) lower in patients with GI-NETs treated with [177Lu]Lu-DOTA-TATE than in those treated with everolimus and BSC, respectively. Similarly, the hazard of progression was 64% (HR 0.36 CI95 0.18-0.70), 54% (HR 0.46 CI95 0.30-0.71) and 79-87% (HR 0.21 CI95 0.13-0.32; HR 0.13 CI95 0.08-0.22) lower in patients with P-NET treated with [177Lu]Lu-DOTA-TATE than in those treated with sunitinib, everolimus and BSC, respectively. The hazard of death was 58% (HR 0.42 CI95 0.25-0.72), 47% (HR 0.53 CI95 0.33-0.87) and 44-64% (HR 0.56 CI95 0.36-0.90; HR 0.34 CI95 0.20-0.57) lower in P-patients with NET treated with [177Lu]Lu-DOTA-TATE than in those treated with sunitinib, everolimus and BSC, respectively. While our results must be interpreted with caution given the non-randomised nature of the comparisons and the potential for residual confounding, the magnitude of the effect sizes we observe and their consistency across comparators suggest that [177Lu]Lu-DOTA-TATE may be a more effective treatment option than everolimus, sunitinib and BSC in advanced, unresectable GEP-NETs.

Comparison of 68Ga-labeled Prostate-specific Membrane Antigen Ligand Positron Emission Tomography/Magnetic Resonance Imaging and Positron Emission Tomography/Computed Tomography for Primary Staging of Prostate Cancer: A Systematic Review and Meta-analysis.

CONTEXT: In December 2020, the US Food and Drug Administration approved a 68Ga-labeled prostate-specific membrane antigen ligand (68Ga-PSMA-11) for positron emission tomography (PET) in patients with suspected prostate cancer (PCa) metastasis who are candidates for initial definitive therapy. 68Ga-PSMA PET is increasingly performed for these patients and is usually combined with computed tomography (CT). In recent years, 68Ga-PSMA PET has been combined with high-resolution magnetic resonance imaging (MRI), which is beneficial for T staging and may further enhance the staging of primary PCa. OBJECTIVE: To compare the diagnostic accuracy of 68Ga-PSMA PET/MRI with 68Ga-PSMA PET/CT for staging of primary PCa. EVIDENCE ACQUISITION: A comprehensive literature search was performed using Embase, PubMed/Medline, Web of Science, Cochrane Library, and Google Scholar up to June 24, 2021 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Risk of bias was assessed using the QUADAS-2 tool. EVIDENCE SYNTHESIS: The search identified 2632 articles, of which 27 were included. The diagnostic accuracy of 68Ga-PSMA PET/MRI, measured as the pooled natural logarithm of diagnostic odds ratio (lnDOR), was 2.27 (95% confidence interval [CI] 1.21-3.32) for detection of extracapsular extension (ECE), 3.50 (95% CI 2.14-4.86) for seminal vesicle invasion (SVI), and 4.73 (95% CI 2.93-6.52) for lymph node metastasis (LNM). For 68Ga-PSMA PET/CT, the analysis showed lnDOR of 2.45 (95% CI 0.75-4.14), 2.94 (95% CI 2.26-3.63), and 2.42 (95% CI 2.07-2.78) for detection of ECE, SVI, and LNM, respectively. The overall risk of bias and applicability concerns were assessed as moderate and low, respectively. CONCLUSIONS: 68Ga-PSMA PET/MRI shows high diagnostic accuracy equivalent to that of 68Ga-PSMA PET/CT for detection of ECE, SVI, and LNM in staging of PCa. There is an urgent need for direct comparison of the two diagnostic tests in future research. PATIENT SUMMARY: The use of radioactively labeled molecules that bind to prostate-specific membrane antigen (68Ga-PSMA) for positron emission tomography (PET) scans combined with either computed tomography (CT) or magnetic resonance imaging (MRI) is increasing for prostate cancer diagnosis. There is a need for direct comparison of the two tests to demonstrate the benefit of 68Ga-PSMA PET/MRI for determining tumor stage in prostate cancer. TAKE HOME MESSAGE: After the recent US Food and Drug Administration approval of 68Ga-labeled prostate-specific membrane antigen ligand (68Ga-PSMA) positron emission tomography (PET) for staging of primary prostate cancer (PCa), it is expected that the use of this imaging modality will increase rapidly. Our review of the literature shows that 68Ga-PSMA PET/magnetic resonance imaging has high diagnostic accuracy equivalent to that of 68Ga-PSMA PET/computed tomography in primary PCa staging. There is an urgent need for direct head-to-head comparison of the two diagnostic tests in future research.

False positive FDG uptake in melanoma patients treated with talimogene laherparepvec (T-VEC).

Talimogene laherparepvec (T-VEC) is a genetically modified herpes simplex virus-1-based oncolytic immunotherapy and has been approved for the local treatment of unresectable (stage IIIB/C and IVM1a) cutaneous melanoma. During T-VEC treatment, tumor response is often evaluated using [18F]2-fluoro-2-deoxy- d-glucose(FDG) positron emission tomography/computed tomography (PET/CT). In a Dutch cohort (n = 173), almost one-third of patients developed new-onset FDG uptake in uninjected locoregional lymph nodes during T-VEC. In 36 out of 53 (68%) patients with new nodal FDG uptake, nuclear medicine physicians classified this FDG uptake as "suspected metastases" without clinical or pathological confirmation in the majority of patients. These false positive results indicate that new-onset FDG uptake in locoregional lymph nodes during T-VEC treatment does not necessarily reflect progressive disease, but may be associated with immune infiltration. In current clinical practice, physicians should be aware of the high false positive rate of FDG uptake during treatment with T-VEC in patients with melanoma. Therefore, pathological examination of lymph node lesions with new FDG uptake is recommended to differentiate between progressive disease and immune infiltration after treatment with T-VEC.