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.

[177Lu]Lu-PSMA-617 as first-line systemic therapy in patients with metastatic castration-resistant prostate cancer: a real-world study.

PURPOSE: The use of [177Lu]Lu-PSMA-617 radioligand therapy has become increasingly recognized as a viable therapeutic approach for patients in the advanced stages of metastatic castration-resistant prostate cancer (mCRPC). However, there is limited data regarding its effectiveness and safety in earlier lines. This study aims to present our institution's experience with [177Lu]Lu-PSMA-617 as a first-line systemic therapy for mCRPC. METHODS: We collected and analyzed data from consecutive mCRPC patients who underwent first-line treatment with [177Lu]Lu-PSMA-617 at our center from 2015 to 2023. The various outcome measures included best prostate-specific antigen-response rate (PSA-RR) (proportion of patients achieving a ≥ 50% decline in PSA); objective radiographic response rate (ORR) (proportion of patients achieving complete or partial radiographic responses); radiographic progression-free survival (rPFS) (measured from treatment initiation until radiographic progression or death from any cause); overall survival (OS) (measured from treatment initiation until death from any cause); and adverse events. RESULTS: Forty treatment-naïve mCRPC patients with PSMA-positive disease on [68Ga]Ga-PSMA-11 PET/CT were included (median age: 68.5 years, range: 45-78; median PSA: 41 ng/mL, range: 1-3028). These patients received a median cumulative activity of 22.2 GBq (range: 5.55-44.4) [177Lu]Lu-PSMA-617 over 1-6 cycles at 8-12 week intervals. A ≥ 50% decline in PSA was observed in 25/40 (62.5%) patients (best PSA-RR). Radiographic responses were evaluated for thirty-eight patients, with thirteen showing partial responses (ORR 34.2%). Over a median follow-up of 36 months, the median rPFS was 12 months (95% confidence interval, CI: 9-15), and the median OS was 17 months (95% CI: 12-22). Treatment-emergent grade ≥ 3 anemia, leucopenia, and thrombocytopenia were noted in 4/40 (10%), 1/40 (2.5%), and 3/40 (7.5%) patients, respectively. CONCLUSION: The findings suggest that [177Lu]Lu-PSMA-617 is a safe and effective option as a first-line treatment in mCRPC. Further trials are needed to definitively establish its role as an upfront treatment modality in this setting.

Efficacy and safety of 225Ac-DOTATATE targeted alpha therapy in metastatic paragangliomas: a pilot study.

PURPOSE: In this study, we aim to evaluate the efficacy and safety of 225AC-DOTATATE targeted alpha therapy in advanced-stage paragangliomas (PGLs). METHODS: Nine (6 males and 3 females) consecutive patients with histologically proven PGLs were treated with 225Ac-DOTATATE targeted alpha therapy (TAT) and concomitant radiosensitizer, capecitabine, at 8-weekly intervals up to a cumulative activity of ~ 74 MBq. The primary endpoint included evaluating therapy response and disease control rate (DCR) using the RECIST 1.1 criteria. Additional secondary endpoints comprised clinical response assessment using EORTC QLQ-H&N35 questionnaire, Karnofsky Performance Scale (KPS), Eastern Cooperative Oncology Group performance status (ECOG), analgesic score (AS), dose alterations of anti-hypertensive drugs (anti-HTN), and the safety and side-effect profile evaluation as per CTCAE criteria version 5.0. RESULTS: Following 225Ac-DOTATATE treatment, morphological response revealed partial response in 50%, stable disease in 37.5%, and disease progression in 12.5%, with a DCR of 87.5%. Similarly, the symptomatic response was remarkable, and anti-HTN drugs were stopped in 25% and reduced in 37.5%. Another significant finding in our study revealed a morphologic DCR of 66.6% (2/3) in patients who failed previous lutetium-177 peptide receptor radionuclide therapy (177Lu-PRRT). Regarding the KPS, ECOG, and AS performance scores, a notable improvement was observed post-225Ac-DOTATATE treatment. The QLQ-H&N35 symptom scores evaluated in seven H&N PGL patients showed significant improvement in all aspects. No improvement in sexual function was noted (P = 0.3559). Despite the significant reduction in the analgesic score post-treatment (P = 0.0031), the QLQ-H&N35 revealed only marginal significance concerning the intake of pain killers (P = 0.1723). No grade III/IV hematological, renal, and hepatological toxicities were noted. CONCLUSION: The evidence from this study suggests 225Ac-DOTATATE therapy is effective and safe in the treatment of advanced-stage PGLs and also reports a clear benefit even in patient's refractory to the previous 177Lu-PRRT.

Biodistribution, pharmacokinetics, dosimetry of [68Ga]Ga-DOTA.SA.FAPi, and the head-to-head comparison with [18F]F-FDG PET/CT in patients with various cancers.

PURPOSE: [68Ga]Ga-labeled fibroblast activation protein inhibitors ([68Ga]Ga-FAPi) have shown promising preclinical and clinical results in PET imaging. The present study aimed to evaluate the biodistribution, pharmacokinetics, and dosimetry of [68Ga]Ga-DOTA.SA.FAPi, another modified FAPi tracer, and performed a head-to-head comparison with [18F]F-FDG PET/CT scans in patients with various cancers. METHODS: In this prospective study, patients underwent both [18F]F-FDG and [68Ga]Ga-DOTA.SA.FAPi PET/CT scans 60 min post-injection (p.i.). Dosimetry studies were conducted in three patients using [68Ga]Ga-DOTA.SA.FAPi serial time-point imaging. The absorbed dose was calculated using OLINDA/EXM 2.2 software. Quantification of the uptake of the tracers was assessed using standardized uptake values corrected for lean body mass (SUL). RESULTS: Fifty-four patients (mean age; 48.4 years) with 14 types of cancers involving 37% breast, 24% lung, 7.4% head and neck (H&N), and remaining 31.6% patients with other histologies were evaluated prospectively. Physiological uptake of [68Ga]Ga-DOTA.SA.FAPi was observed in the liver, kidneys, pancreas, heart contents, and to a lesser extent in the lacrimals, oral mucosa, salivary glands, and thyroid glands. Uptake in the target lesions on [68Ga]Ga-DOTA.SA.FAPi scan was initiated at 10 min, and no additional lesions were detected in the delayed acquisition time points. The pancreas was the organ with the highest absorbed dose (5.46E-02 mSv/MBq). While the patient-based comparison between the radiotracers revealed complete concordance in the detection of primary, pleural thickening, bone and liver metastases, and second primary malignancy, discordant findings were observed in the detection of lymph node (7.5%), lung nodules (5.6%), and brain metastases (2%). According to the site of primary disease, patients with H&N cancers demonstrated the highest SULpeak and average (avg) values on [68Ga]Ga-DOTA.SA-FAPi which was similar to the values of [18F]F-FDG [(SULpeak: 15.4 vs. 14.2; P-0.680) (SULavg: 8.3 vs. 7.9; P-0.783)]. The lowest uptake was observed in lung cancers with both the radiotracers [(SULpeak: 5.8 vs. 7.4; P-0.238) (SULavg: 4.9 vs. 5.3; P-0.313)]. A significantly higher SULpeak and SULavg for brain metastases to normal brain parenchyma ratios were observed on [68Ga]Ga-DOTA.SA.FAPi in contrast to the [18F]F-FDG values {SULpeak: median: 59.3 (IQR: 33.5-130.8) versus 1.5 (1-2.3); P-0.028}. Except for brain metastases, comparable SULpeak and average values were noted between the radiotracers in all other regions of metastases with no significant difference. CONCLUSION: [68Ga]Ga-DOTA.SA.FAPi is a promising alternative among the FAPI class of molecules and performed well as compared to standard-of-care radiotracer [18F]F-FDG in the diagnosis of various cancers.

Broadening horizons with 225Ac-DOTATATE targeted alpha therapy for gastroenteropancreatic neuroendocrine tumour patients stable or refractory to 177Lu-DOTATATE PRRT: first clinical experience on the efficacy and safety.

PURPOSE: The objective of this study was to investigate and present the early results on the efficacy, safety, and quality of life of 225Ac-DOTATATE targeted alpha therapy (TAT) in patients with advanced, progressive, 177Lu-DOTATATE refractory, and somatostatin receptor (SSTR) expressing metastatic GEP-NETs. METHODS: In this prospective study, we recruited patients with metastatic GEP-NETs who were stable or progressive disease on 177Lu-DOTATATE therapy. Systemic TAT using 225Ac-DOTATATE was performed in all the patients with 225Ac-DOTATATE (100 kBq/kg body weight) at an interval of 8 weeks. The primary end point was to assess the objective response (measured by RECIST 1.1 and functional M.D. Anderson criteria). The secondary end points included biochemical response assessment as per the Italian Trials in Medical Oncology (ITMO), adverse event profile as per CTCAE v5.0, and clinical response assessment by the quality of life (assessed with EORTC QLQ-GI.NET21 patient-based questionnaire). RESULTS: Between April 2018 and March 2019, 32 patients (17 females, 15 males, mean age 52 ± 9.2 years, 35-72 years) with either stable disease after completing 177Lu-DOTATATE therapy (14, 44%) or progressive disease on 177Lu-DOTATATE therapy (18, 56%) were included in the study. The morphological response was assessed in 24/32 patients that revealed partial remission in 15 and stable disease in 9. There was no documented disease progression or deaths in the median follow-up of 8 months (range 2-13 months). There was a significant decrease in the plasma chromogranin level post-225Ac-DOTATATE therapy (P < 0.0001). CONCLUSION: Our short-term clinical results indicate 225Ac-DOTATATE TAT as a promising treatment option which adds a new dimension in patients who are refractory to 177Lu-DOTATATE therapy or have reached the maximum prescribed cycles of 177Lu-DOTATATE therapy.

Evaluation of [68Ga]Ga-DATA-TOC for imaging of neuroendocrine tumours: comparison with [68Ga]Ga-DOTA-NOC PET/CT.

PURPOSE: Recently, the new hybrid chelator DATA (6-amino-1,4-diazepine-triacetate) has been introduced, which has the advantage of high yield and radiolabelling of DATA-based octreotide derivative (TOC) at room temperature in contrast to tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) that needs 95 °C for effective labelling. However, the diagnostic potential of DATA-TOC has not been studied with other chelators in humans. The aim of this study was to compare the diagnostic efficacy of [68Ga]Ga-DATA-TOC with [68Ga]Ga-DOTA-NOC (which is the current standard for imaging neuroendocrine tumours (NET)) in patients of gastroenteropancreatic neuroendocrine tumours (GEP-NETs). METHODS: Fifty patients (thirty-one males and nineteen females) with biopsy-proven GEP-NETs were included in the study. Patients age ranged from 14 to 75 years (mean 46.11 years). All patients underwent two PET studies with [68Ga]Ga-DATA-TOC and [68Ga]Ga-DOTA-NOC. Images were evaluated visually and semi-quantitatively using maximum standardized uptake values (SUVmax) of tumour, mediastinum and liver. Tumour-to-liver (T/L) and tumour-to-mediastinum (T/M) SUVmax ratios were computed. For the purpose of comparison, patient-wise as well as lesion-wise analysis was carried out. The nonparametric-related samples Wilcoxon signed-rank test was used for comparison of the SUVmax values and ratios. RESULTS: On visual evaluation, the biodistribution and image quality of [68Ga]Ga-DATA-TOC was similar to [68Ga]Ga-DOTA-NOC. Physiological liver uptake was lower in [68Ga]Ga-DATA-TOC as compared with [68Ga]Ga-DOTA-NOC, 7.65 ± 5.37 vs 8.94 ± 5.95 (p = 0.009), respectively. On a patient-wise analysis, both [68Ga]Ga-DATA-TOC and [68Ga]Ga-DOTA-NOC were lesion-positive in the 44 patients (88%) and were negative in the 6 patients (12%). On a lesion-based analysis, [68Ga]Ga-DATA-TOC had 98.6% concordance with [68Ga]Ga-DOTA-NOC (232 out of 235 lesions detected). The target tumour SUVmax on [68Ga]Ga-DATA-TOC and [68Ga]Ga-DOTA-NOC were 36.63 ± 32.24 and 40.82 ± 36.89, respectively (p = 0.097). The T/L SUVmax ratios were not significantly different (5.99 ± 5.52 vs 5.67 ± 4.96, p = 0.77). CONCLUSION: [68Ga]Ga-DATA-TOC PET/CT imaging produced results that were comparable with [68Ga]Ga-DOTA-NOC. It, thus, has potential utility as an effective and safe alternative to 68Ga-DOTA-NOC with the added benefit of ease, cost-effective and improved yield of instant kit-type synthesis.

Radioligand Therapy With 177Lu-PSMA for Metastatic Castration-Resistant Prostate Cancer: A Systematic Review and Meta-Analysis.

OBJECTIVE. Several clinical studies have shown the efficacy of 177Lu-labeled prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) for metastatic castration-resistant prostate cancer (mCRPC). The purpose of this article is to present results of a systematic review and meta-analysis aimed at compiling and outlining efficacy and safety data on 177Lu-PSMA RLT for mCRPC across all studies published to date. CONCLUSION. The results of the systematic review and meta-analysis suggest that 177Lu-PSMA RLT is an effective treatment of advanced-stage mCRPC that is refractory to standard therapeutic options and that it has a low toxicity profile. High-level evidence from randomized control trials is crucial for confirming the effectiveness of 177Lu-PSMA RLT and for instituting this therapy in the routine clinical care of patients with mCRPC.

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

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

Evaluation of bone-seeking novel radiotracer 68Ga-NO2AP-Bisphosphonate for the detection of skeletal metastases in carcinoma breast.

PURPOSE: The successful labelling of bisphosphonates (BP) with 68Ga using macrocyclic chelators such as the based triazacyclononane (NO2AP) is a step forward in the in-house availability of a novel bone-seeking PET radiopharmaceutical with dual advantage of PET/CT imaging and generator production. In this study, we compared the novel generator-based skeletal radiotracer 68Ga-1,4,7-triazacyclonone-1,4-diacetic acid (68Ga-NO2AP-BP) with sodium fluoride (18F-NaF) for the detection of skeletal metastases in breast cancer patients. In addition, dosimetric analysis of 68Ga-NO2AP-BP was performed in a subset of patients. METHODS: This was a prospective study of histopathologically proven cases of breast cancer patients who were referred for bone scintigraphy and underwent positron emission tomography/computed tomography (PET/CT) with 18F-NaF and 68Ga-NO2AP-BP within a week in random order. The scans of each patient were compared both qualitatively for image quality and quantitatively for number of lesions and SUVmax of lesions. Dosimetric analysis was performed in five patients. Their PET/CT scans were acquired at multiple time points and urine and blood samples were collected. Dosimetric calculations were performed using OLINDA/EXM 1.1 software. Statistical analysis was done using Stata 13 (StataCorp) software package. An agreement analysis regarding number of lesions detected with the two skeletal radiotracers was carried out. RESULTS: The image quality of 68Ga-NO2AP-BP PET/CT scans were comparable to that of 18F-NaF. There was no statistically significant difference in the SUVmax of lesions, normal bone and lesion to background ratio between the two skeletal radiotracers. There was good agreement in the number of lesions detected by both skeletal radiotracers. The mean whole body effective dose for 68Ga-NO2AP-BP was 0.00583 mSv/MBq and the effective dose equivalent was 0.0086 mSv/MBq. CONCLUSION: The excellent lesion detection agreement between 68Ga-NO2AP-BP and 18F-NaF favours the former as an alternative for skeletal scintigraphy in centres without an on-site cyclotron. The favourable dosimetric results and its potential to be used as a theranostic agent makes it an important generator-based skeletal radiotracer.

An approach for conjugation of (177) Lu- DOTA-SCN- Rituximab (BioSim) & its evaluation for radioimmunotherapy of relapsed & refractory B-cell non Hodgkins lymphoma patients.

BACKGROUND & OBJECTIVES: The prerequisite of radioimmunotherapy is stable binding of a radionuclide to monoclonal antibodies, which are specific to the tumour-associated antigen. Most B-cell lymphomas express CD20 antigen on the surface of the tumour cells, making it a suitable target for therapeutic radioactive monoclonal antibodies. In the present study, the immunoconjugate of biosimilar Rituximab (Reditux™) and macrocyclic chelator, p-SCN-Bz-DOTA, was prepared and radiolabelled with Lutetium-177 followed by quality control procedures. METHODS: Rituximab(BioSim) was desalted with sodium bicarbonate (0.1M, pH 9.0) and incubated with DOTA-SCN (1:50). The effectiveness of the conjugation was evaluated by determining the number of chelators per antibody molecule. This conjugate was radiolabelled with Lutetium-177 and purified using PD10 column. The quality control parameters like pH, clarity, radiochemical purity, in vitro stability and sterility were studied. Immunoreactivity of 177 Lu-DOTA-Rituximab (BioSim) was assessed using RAMOS cells. The radioimmunoconjugate (RIC) after stringent quality assurance was injected in three patients and the biodistribution profile was analysed. RESULTS: An average of 4.25 ± 1.04 p-SCN-Bz-DOTA molecules could be randomly conjugated to a single molecule of Rituximab (BioSim).The radiochemical purity of the labelled antibody was > 95 per cent with preserved affinity for CD20 antigen. The final preparation was stable up to about 120 h when tested under different conditions. A favourable biodistribution profile was observed with liver showing the maximum uptake of the RIC. INTERPRETATION & CONCLUSIONS: A favourable radiochemical purity, stability and biodistribution of the radiolabelled immunoconjugate indicate that clinical trials for evaluation of toxicity and efficacy of 177 Lu-DOTA-antiCD20 antibody-Rituximab (BioSim) in patients of relapsed and refractory non Hodgkin's lymphoma can be considered.

Complete Response to 177 Lu-DOTATATE PRRT in a 9-Year-Old Child With Metastatic Carotid Body Paraganglioma.

ABSTRACT: We present a case involving a 9-year-old boy diagnosed with metastatic carotid body paraganglioma. The metastases were detected in cervical lymph nodes and lungs using 68 Ga-DOTANOC PET/CT imaging. The patient received peptide receptor radionuclide therapy with 177 Lu-DOTATATE. Following 3 treatment cycles, a significant improvement was observed in the metastatic lesions. After 4 cycles, the patient achieved a complete response, with a cumulative administered activity of 16.65 GBq during the therapy. This case underscores the effectiveness of using 177 Lu-DOTATATE in managing metastatic carotid body paraganglioma, offering promising results in terms of tumor regression and overall therapeutic response.

Promising Therapeutic Activity of 177 Lu-PSMA-617 in Synchronous High-Volume Metastatic Hormone-Sensitive Prostate Cancer : A Pilot Experience.

PURPOSE: 177 Lu-PSMA-617 has been shown to improve survival outcomes in patients with end-stage metastatic castration-resistant prostate cancer. However, data in earlier lines remain limited. In this study, we intended to evaluate the efficacy and safety of 177 Lu-PSMA-617 in patients with synchronous high-volume metastatic hormone-sensitive prostate cancer (mHSPC). PATIENTS AND METHODS: Hormone-sensitive prostate cancer patients with synchronous high-volume metastases (defined as ≥4 skeletal metastases with ≥1 extra-axial site or any visceral metastasis) showing high PSMA expression on 68 Ga-PSMA-11 PET/CT and ineligible/unwilling for conventional chemohormonal treatment options were selected. Approximately, ~5.55-7.4 GBq of 177 Lu-PSMA-617 was administered intravenously at 8-12 weeks intervals, up to 6 cycles. All patients underwent concomitant androgen deprivation therapy/orchiectomy. The outcome measures included the proportion of patients achieving an undetectable serum prostate-specific antigen (PSA) (ie, ≤0.2 ng/mL) at any time point after therapy, best PSA response rate, objective radiographic response rate, radiographic progression-free survival, overall survival, and adverse events. RESULTS: Ten patients with high-volume mHSPC received a median cumulative activity of 32.4 GBq (range, 7.4-44.4) of 177 Lu-PSMA-617 over 1-6 cycles. Five patients (50%) achieved an undetectable PSA with 9 patients (90%) showing a ≥50% decline in PSA from baseline. Nine patients underwent radiological follow-up, of which 7 (77.8%) had an objective response. The median radiographic progression-free survival was 24 months (95% confidence interval, 18-30), whereas the median overall survival was not reached. None of the patients had any grade 3/4 adverse event. CONCLUSIONS: 177 Lu-PSMA-617 seems to be a promising efficacious and safe treatment option for patients with synchronous high-volume mHSPC.

Head-to-Head Comparison of [68Ga]Ga-DOTA.SA.FAPi and [68Ga]Ga-DOTANOC Positron Emission Tomography/Computed Tomography Imaging for the Follow-Up Surveillance of Patients with Medullary Thyroid Cancer.

Background: A theranostic probe for accurate staging and treatment is crucial for the management of medullary thyroid cancers (MTCs). The abundance of stroma in most of thyroid cancers, including MTC, opens new avenues for selecting cancer-associated fibroblasts (CAFs) as new molecular imaging and therapeutic targets. [68Ga]Ga-labeled fibroblast activation protein inhibitor (FAPi) molecules have gained importance as alternative molecular imaging agents in the imaging of thyroid cancers. The purpose of this study was to compare the detection efficiency of primary and metastatic lesions of MTCs between [68Ga]Ga-DOTA.SA.FAPi and [68Ga]Ga-DOTANOC positron emission tomography (PET) radiotracers. Materials and Methods: In this retrospective study, [68Ga]Ga-DOTANOC and [68Ga]Ga-DOTA.SA.FAPi PET/CT (computed tomography) images were compared using patient-based and lesion-based analysis in patients with MTC for follow-up assessment. The quantitative assessment included comparing standardized uptake values corrected for lean body mass (SULpeak) and tumor-to-background ratios (TBR). The findings on both scans were validated with the morphological findings of the diagnostic CT. Results: Twenty-seven patients (21 males and 6 females) with a mean age of 42.4 ± 13.2 years (range 14-66 years) were included in the study. [68Ga]Ga-DOTA.SA.FAPi had similar sensitivities as that of [68Ga]Ga-DOTANOC PET/CT for detecting primary tumors (100% [18 of 18] vs. 94.4% [17 of 18], p = 0.979) involved lymph nodes (98.3% [118 of 120] vs. 95% [114 of 120], p = 0.288), and brain metastases (100%). [68Ga]Ga-DOTA.SA.FAPi demonstrated significantly higher sensitivities than [68Ga]Ga-DOTANOC PET/CT for detecting lung nodules (93.5% [87 of 93] vs. 68.9% [64 of 93], p < 0.0001), liver (100% [105 of 105] vs. 46.4% [49 of 105], p < 0.0001), bone (92.4% [110 of 119] vs. 76.5% [91 of 119], p = 0.001), and pleural metastases 98.2% versus 0%. Higher uptake values and TBR values were reported with [68Ga]Ga-DOTA.SA.FAPi compared with that of [68Ga]Ga-DOTANOC. Conclusion: [68Ga]Ga-DOTA.SA.FAPi outperformed [68Ga]Ga-DOTANOC PET/CT in the detection of distant metastases with both patient-based and lesion-based analysis in MTCs.

Novel Generation of FAP Inhibitor-Based Homodimers for Improved Application in Radiotheranostics.

Radiopharmaceuticals based on the highly potent FAP inhibitor (FAPi) UAMC-1110 have shown great potential in molecular imaging, but the short tumor retention time of the monomers do not match the physical half-lives of the important therapeutic radionuclides 177Lu and 225Ac. This was improved with the dimer DOTAGA.(SA.FAPi)2, but pharmacological and radiolabeling properties still need optimization. Therefore, the novel FAPi homodimers DO3A.Glu.(FAPi)2 and DOTAGA.Glu.(FAPi)2. were synthesized and quantitatively radiolabeled with 68Ga, 90Y, 177Lu and 225Ac. The radiolabeled complexes showed high hydrophilicity and were generally stable in human serum (HS) and phosphate-buffered saline (PBS) at 37 °C over two half-lives, except for [225Ac]Ac-DOTAGA.Glu.(FAPi)2 in PBS. In vitro affinity studies resulted in subnanomolar IC50 values for FAP and high selectivity for FAP over the related proteases PREP and DPP4 for both compounds as well as for [natLu]Lu-DOTAGA.Glu.(FAPi)2. In a first proof-of-principle patient study (medullary thyroid cancer), [177Lu]Lu-DOTAGA.Glu.(FAPi)2 was compared to [177Lu]Lu-DOTAGA.(SA.FAPi)2. High uptake and long tumor retention was observed in both cases, but [177Lu]Lu-DOTAGA.Glu.(FAPi)2 significantly reduces uptake in non-target and critical organs (liver, colon). Overall, the novel FAPi homodimer DOTAGA.Glu.(FAPi)2 showed improved radiolabeling in vitro and pharmacological properties in vivo compared to DOTAGA.(SA.FAPi)2. [177Lu]Lu-DOTAGA.Glu.(FAPi)2 and [225Ac]Ac-DOTAGA.Glu.(FAPi)2 appear promising for translational application in patients.

Survival Outcomes in Metastatic Gastroenteropancreatic Neuroendocrine Tumor Patients receiving Concomitant 225Ac-DOTATATE Targeted Alpha Therapy and Capecitabine: A Real-world Scenario Management Based Long-term Outcome Study.

Rationale: Although the short-term results of targeted alpha therapy (TAT) with 225Ac-DOTATATE in gastroenteropancreatic neuroendocrine tumors (GEP-NETs) have proven effective, none have assessed the long-term outcome results. In this study, we aimed to evaluate the long-term outcome of 225Ac-DOTATATE targeted alpha therapy (TAT) in patients with somatostatin receptor (SSTR)-expressing advanced-stage metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Methods: Patients with 68Ga-DOTANOC PET/CT scans showing moderate-to-high SSTR expression were recruited. Systemic TAT was performed in 91 adults with GEP-NET [54 males, and 37 females] mean age 54 years (y) (range: 25-75y)] using 225Ac-DOTATATE (100-120 kBq/kg body weight). All patients were given capecitabine therapy as a radiosensitizer (dose 2 g/day) from day 0 to 14 of every 225Ac-DOTATATE treatment cycle. Patients were categorized into three groups based on the status of prior 177Lu-PRRT: prior 177Lu-PRRT-refractory-group; prior 177Lu-PRRT-disease-control group; and 177Lu-PRRT naïve group. Primary endpoints were overall survival (OS), and secondary endpoints included progression-free survival (PFS), objective tumour response, clinical response, and the assessment of treatment-related toxicities. Results: Among the 91 patients, 57 underwent prior 177Lu-DOTATATE therapy [24 disease controlled (PR/SD), 33 progressive diseases (PD)]. A total of 453 225Ac-DOTATATE TAT cycles were administered [median four cycles per patient; range 1-10] in a median follow-up duration of 24 months (range 5-41mo). Median OS was not attained with a 24-month overall survival probability of 70.8%. In multivariate analysis, prognostic factors associated with a poor OS included, the presence bone metastases [HR: 2.501; 95% CI: 1.826 - 5.791; P<0.032], and 225Ac-DOTATATE therapy refractory disease [HR: 8.781; 95% CI: 3.843 - 20.062; P<0.0001]. Median PFS was also not reached with a 24-month progression-free survival probability of 67.5%. The multivariate analysis revealed only 177Lu-PRRT refractory disease significantly associated with a reduced PFS. [HR: 14.338; 95% CI: 1.853 - 97.698; P = 0.011]. Two of 79 patients (2.5%) with assessable disease experienced complete response; 38 (48%) had a partial response, 23 (29%) had SD, and 16 (20.2%) had PD. PD was observed in more patients from the prior 177Lu-PRRT-refractory group (11/33; 34%) as compared to 177Lu-PRRT-naïve patients (4/24; 11%), P-0.056. Patients from the prior 177Lu-PRRT-refractory group had the highest risk of poor PFS [HR:13.91; 95% CI: 4.45 - 42.271; P = 0.0009]. A significant clinical benefit was achieved post 225Ac-DOTATATE therapy with minimal treatment-related toxicities. Conclusion: The long-term results reveal 225Ac-DOTATATE TAT has shown promising results and improves overall survival, even in patients refractory to prior 177Lu-DOTATATE treatment, with transient and acceptable adverse effects.

First-in-Human Experience With 177Lu-DOTAGA.(SA.FAPi)2 Therapy in an Uncommon Case of Aggressive Medullary Thyroid Carcinoma Clinically Mimicking as Anaplastic Thyroid Cancer.

ABSTRACT: A 56-year-old man was diagnosed with calcitonin negative, plasma chromogranin A-positive, immunohistochemistry-negative, high-grade MTC (medullary thyroid cancer) behaving clinically like anaplastic thyroid cancer and presented with progressive disease after conventional therapies. A theranostic approach of 68Ga-DOTA.SA.FAPi-guided 177Lu-DOTAGA.(SA.FAPi)2 radionuclide therapy was administered on compassionate grounds as per the Declaration of Helsinki because known standard lines of treatment were ineffective. Treatment with a single cycle of 1.65 GBq 177Lu-DOTAGA.(SA.FAPi)2 demonstrated a sustainable reduction in the neck mass with significant improvement in the quality of life of the patient. 177Lu-DOTAGA.(SA.FAPi)2 is a potential theranostic option for high-grade MTC refractory to standard therapeutic options.

Novel Fibroblast Activation Protein Inhibitor-Based Targeted Theranostics for Radioiodine-Refractory Differentiated Thyroid Cancer Patients: A Pilot Study.

Background: This exploratory study was meant to assess clinical and safety data with a novel fibroblast activation protein inhibitor-based targeted theranostics as a salvage treatment option in radioiodine-refractory differentiated thyroid cancer (RR-DTC) patients who had progressed on tyrosine kinase inhibitors. Methods: Patients with metastatic RR-DTC who progressed on sorafenib/lenvatinib were prospectively recruited. If [68Ga]Ga-DOTA.SA.FAPi positron emission tomography/computed tomography scan demonstrated moderate-to-excellent uptake in metastases, and patients had given informed consent, they received intravenous [177Lu]Lu-DOTAGA.(SA.FAPi)2 as therapy at eight-weekly intervals. The primary endpoints were thyroglobulin (Tg) response and functional imaging response. The secondary endpoints were visual analog score (VAS) and Eastern Cooperative Oncology Group (ECOG) performance status. The grading of toxicities was performed by using Common Terminology Criteria for Adverse Events (CTCAEV5.0). The sequential images were acquired by a dual-headed gamma camera, and dosimetric calculations were performed by using OLINDA/EXM V2.1. Results: Fifteen patients were recruited [age: 55 ± 9 years (range: 39-67)]. [177Lu]Lu-DOTAGA.(SA.FAPi)2 had median whole-body Teff of 88.06 hours (interquartile range [IQR]: 86.6-99). The colon was identified as a critical organ. The whole-body effective dose was 1.62E-01 ± 1.53E-02 mSv/MBq. A total of 45 cycles were administered, and the median cumulative administered activity was 8.2 ± 2.7 GBq (range 5.5-14 GBq). The median absorbed doses to the tumor lesions were 1.08E+01 (IQR: 4.16E+00 to 8.97E+01) mSv/MBq per cycle. The Serum Tg level significantly decreased after treatment [(median Tg: baseline-10,549 ng/mL (IQR: 3066.5-39,450) versus at the time of assessment: 5649 ng/mL (IQR: 939.5-17,099), p = 0.0005)]. Molecular response assessment revealed no complete response; however, partial response was documented in four, and stable disease in three patients. The VASmax scores [pre-therapy: 9 (IQR: 8-10) versus follow-up: 6 (3-6) (p-0.0001)], and ECOG [3, (IQR: 2-3 vs. 2, (IQR: 2-3) (p-0.0078)] performance scores significantly improved after treatment. None of the patients experienced grade III/IV hematological, renal, or hepatotoxicity. Conclusion: These preliminary data suggest that the novel molecule [177Lu]Lu-DOTAGA.(SA.FAPi)2 is safe, seems effective, and, most importantly, opens up a new avenue for the treatment of aggressive RR-DTC patients who have exhausted all standard line of treatments.