Meeting report from the Prostate Cancer Foundation PSMA-directed radionuclide scientific working group

INTRODUCTION

The Prostate Cancer Foundation (PCF) convened a PSMA-Directed Radionuclide Scientific Working Group on November 14, 2017, at Weill Cornell Medicine, New York, NY.

METHODS

The meeting was attended by 35 global investigators with expertise in prostate cancer biology, radionuclide therapy, molecular imaging, prostate-specific membrane antigen (PSMA)-targeted agents, drug development, and prostate cancer clinical trials. The goal of this meeting was to discuss the potential for using PSMA-targeted radionuclide agents for the treatment of advanced prostate cancer and to define the studies and clinical trials necessary for validating and optimizing the use of these agents.

RESULTS

Several major topic areas were discussed including the overview of PSMA biology, lessons and applications of PSMA-targeted PET imaging, the nuances of designing PSMA-targeted radionuclide agents, clinical experiences with PSMA-targeted radionuclides, PCF-funded projects to accelerate PSMA-targeted radionuclide therapy, and barriers to the use of radionuclide treatments in widespread clinical practice.

DISCUSSION

This article reviews the major topics discussed at the meeting with the goal of promoting research that will validate and optimize the use of PSMA-targeted radionuclide therapies for the treatment of advanced prostate cancer.

Abstract CT015: Safety and long-term efficacy of radioligand therapy using Lu-177 labeled PSMA ligands in metastatic prostate cancer: A single center experience over 5 years

Aim: Metastatic prostate cancer (mPC) has still a poor prognosis. First- and second-line chemotherapy with docetaxel or cabazitaxel is often toxic and prolongs life by only a few months. Also novel agents like abiraterone, enzalutamide or Ra-223-chloride confer a limited survival benefit. Prostate-specific membrane antigen (PSMA) is a glutamate carboxypeptidase II overexpressed especially in poorly differentiated prostate cancer (1) and is a very attractive target for diagnosis and therapy (theranostics) with radiolabeled small molecules. Internalization and retention within the tumor cell provides very promising and highly selective treatment effects of multiple metastases with PSMA radioligand therapy (PRLT) (2-5).

Methods: 224 mPC patients (mean age 71 years, mean Gleason score 8), screened by Ga-68 PSMA or F-18 DCFPyl PET/CT imaging, were treated with 1 - 9 cycles (3.5 - 12 GBq Lu-177 PSMA per cycle) between April 2013 and October 2017 and included in the intention to treat analysis with a median follow-up time of 16 months (3 - 55). Previous treatments were surgery (154), external beam radiation (151), chemotherapy (110), androgen deprivation (206) and Ra-223 chloride (19). The serum prostate antigen (PSA) levels were monitored before and after therapy. Response to therapy was also determined by RECIST as well as according to molecular imaging criteria using standardized uptake values (SUV) on Ga-68 PSMA PET/CT studies. Hematological and organ toxicity was documented according to CTCAE v4.03.

Results: Reduction in serum PSA was observed in 157/224 (70%) patients; 121/224 patients (54%) demonstrated a PSA decline by >50%, best response was complete remission with undetectable PSA. Ga-68 PSMA PET/CT after at least 2 PRLT cycles in 200 patients demonstrated complete remission in 6 (3%), partial remission in 70 (35%), stable disease in 55 (27.5%) and progressive disease in 69 (34.5%) patients. RECIST revealed 46 (23%) partial remissions, 6 (3%) complete remissions, 84 (42%) with stable disease and 64 (32%) disease progressions. The median overall survival was 27 months. Median progression-free survival was 18 months. No severe (G3-4) bone marrow toxicity was observed and patients didn't show any evidence of nephrotoxicity or any other significant organ toxicity. Mild xerostomia occurred in less than 3% of all patients.

Conclusion: Lu-177 PSMA radioligand therapy appears to be effective for the treatment of metastatic prostate cancer with only minimal toxicity, offering a significant benefit in overall and progression-free survival even in patients whose disease had progressed despite all standard treatments. Randomized controlled studies are required to best determine the place of this theranostic approach in the management of mPC.

Citation Format: Harshad R. Kulkarni, Thomas Langbein, C Atay, Aviral Singh, Christiane Schuchardt, Coline Lehmann, Martin Pomper, Kenneth J. Pienta, Richard P. Baum. Safety and long-term efficacy of radioligand therapy using Lu-177 labeled PSMA ligands in metastatic prostate cancer: A single center experience over 5 years [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT015.

Health-Related Quality of Life in Patients With Progressive Midgut Neuroendocrine Tumors Treated With 177Lu-Dotatate in the Phase III NETTER-1 Trial

Purpose Neuroendocrine tumor (NET) progression is associated with deterioration in quality of life (QoL). We assessed the impact of ¹⁷⁷Lu-Dotatate treatment on time to deterioration in health-related QoL. Methods The NETTER-1 trial is an international phase III study in patients with midgut NETs. Patients were randomly assigned to treatment with ¹⁷⁷Lu-Dotatate versus high-dose octreotide. European Organisation for Research and Treatment of Cancer quality-of-life questionnaires QLQ C-30 and G.I.NET-21 were assessed during the trial to determine the impact of treatment on health-related QoL. Patients completed the questionnaires at baseline and every 12 weeks until tumor progression. QoL scores were converted to a 100-point scale according to European Organisation for Research and Treatment of Cancer instructions, and individual changes from baseline scores were assessed. Time to QoL deterioration (TTD) was defined as the time from random assignment to the first QoL deterioration ≥ 10 points for each patient in the corresponding domain scale. All analyses were conducted on the intention-to-treat population. Patients with no deterioration were censored at the last QoL assessment date. Results TTD was significantly longer in the ¹⁷⁷Lu-Dotatate arm (n = 117) versus the control arm (n = 114) for the following domains: global health status (hazard ratio [HR], 0.406), physical functioning (HR, 0.518), role functioning (HR, 0.580), fatigue (HR, 0.621), pain (HR, 0.566), diarrhea (HR, 0.473), disease-related worries (HR, 0.572), and body image (HR, 0.425). Differences in median TTD were clinically significant in several domains: 28.8 months versus 6.1 months for global health status, and 25.2 months versus 11.5 months for physical functioning. Conclusion This analysis from the NETTER-1 phase III study demonstrates that, in addition to improving progression-free survival, ¹⁷⁷Lu-Dotatate provides a significant QoL benefit for patients with progressive midgut NETs compared with high-dose octreotide.

Theranostics of prostate cancer: from molecular imaging to precision molecular radiotherapy targeting the prostate specific membrane antigen

Alterations at the molecular level are a hallmark of cancer. Prostate cancer is associated with the overexpression of prostate-specific membrane antigen (PSMA) in a majority of cases, predominantly in advanced tumors, increasing with the grade or Gleason's score. PSMA can be selectively targeted using radiolabeled PSMA ligands. These small molecules binding the PSMA can be radiolabeled with γ-emitters like ^99mTc and ¹¹¹In or positron emitters like ⁶⁸Ga and ¹⁸F for diagnosis as well as with their theranostic pairs such as ¹⁷⁷Lu (β-emitter) or ²²⁵Ac (α-emitter) for therapy. This review summarizes the theranostic role of PSMA ligands for molecular imaging and targeted molecular radiotherapy, moving towards precision oncology.

How to Overcome the Disturbing Effects of Human Anti-Mouse Antibodies (Hama) on in Vitro Assays

The development of human anti-mouse antibodies (HAMA) is a common immune response in patients with ovarian carcinoma after repeated injections of murine anti-CA 125 monoclonal antibodies for immunoscintigraphy. As a tumor marker with significant diagnostic value CA 125 is routinely measured in the follow-up of tumor patients by immunoradiometric assays (IRMA) based on murine anti-CA 125 monoclonal antibodies. HAMA may cause false-positive findings in a CA 125-IRMA. In this report our group demonstrates a simple way of eliminating HAMA by protein A/G affinity chromatography allowing the reliable detection of the tumor marker CA 125 in the serum of patients with ovarian carcinoma.

Radioimmunoscintigraphy Using Monoclonal Antibodies to CEA, CA 19-9 and CA 125

131I labelled F (ab’)2 fragments of monoclonal antibodies against CA 19-9 and CEA (“radioimmunococktail” IMACIS 1) were used in a prospective study (n = 60 patients) and in a retrospective study (n = 32 patients) for the detection of colorectal carcinomas (n = 67) and other gastrointestinal CEA/CA 19-9-producing tumors (n = 32). Sensitivity was 82% and specificity 90%. Immunoscintigraphy proved useful and complementary to CT scan and sonography, especially in the diagnosis of pelvic recurrences and intra-abdominal metastases.

In addition, monoclonal antibody OC 125 (IMACIS 2) was used for the detection of ovarian carcinomas (n = 10) and other CA 125 producing tumors. Immunoscintigraphy was positive in all patients (n = 18) suggesting that this radioimmunological approach could be of use in the staging, therapeutic control and earlier diagnosis of recurrent epithelial ovarian carcinoma.

A Preliminary Study on the Functional Analysis of Peripheral Blood Lymphocytes from Ovarian Cancer Patients Developing Hama after Immunoscintigraphy

In the follow-up of ovarian cancer patients, rising levels of the tumor-associated antigen CA 125 are an indication for immunoscintigraphy. Human anti-mouse antibodies (HAMA) are frequently found after immunoscintigraphy with murine MAb directed against CA 125. Since we observed that patients developing high HAMA-levels in serum remained free of tumor or had stable disease, we examined the cytotoxic activity of peripheral blood lymphocytes (PBL) by a fluorescence-based assay. Our results demonstrate that PBLs of patients with high anti-idiotypic antibodies show an increased cytotoxic activity (by a factor of 4) compared to those of patients with low HAMA levels. The clinical course of the patients after the first injection of murine monoclonal antibody was observed over a period of 1 to 3 years. Improvement or deterioration of patients ‘ clinical condition corresponded with the results obtained by functional analysis. Further investigations concerning the course of cytotoxic activity in HAMA-positive patients will have to clarify HAMA's role in the immune response.

Tumor Markers, Liver Function Tests and Symptoms in 115 Patients with Isolated Colorectal Liver Metastases

Development of the hybridoma technique has made the identification of several new tumor antigens possible. Although it was hoped that they would be more tumor-specific, none of these markers are found exclusively in tumor or in serum of tumor patients. Compared with carcinoembryionic antigen (CEA) and liver function tests, the roles of these markers (CA 19-9, CA 125, CA 15-3) were prospectively evaluated in 115 patients with colorectal liver metastases. Patients were classified according to tumor volume (T1 <25%, T2 25-75%, T3 >75%), and the extension of infiltration (solitary/multiple/diffuse; unilateral, bilateral). Patients with benign liver or biliary disease served as a control group (n=63). Overall sensitivity was 87% for *1 , 50% for *2 and 38% for *3 , with a significant correlation with tumor size. CEA serum levels were elevated in 88% of all patients. CA 19-9 was less sensitive: positive in 59%. Because of some complementary elevations, the combined use of CEA, CA 19-9 and CA 125 raised sensitivity to 94%. CA 19-9 and LDH could be useful for confirmation because of their higher specificity; however, the specificity of CEA rose to 93% on using a cut-off of 10 ng/ml instead of 3 ng/ml. The results indicate that CEA and CA 19-9 as well as liver function tests are helpful for preoperative staging in conjunction with imaging procedures before liver resection or regional chemotherapy.

Results and adverse events of personalized peptide receptor radionuclide therapy with 90Yttrium and 177Lutetium in 1048 patients with neuroendocrine neoplasms

Introduction

Peptide receptor radionuclide therapy (PRRT) of patients with somatostatin receptor expressing neuroendocrine neoplasms has shown promising results in clinical trials and a recently published phase III study.

Methods

In our center, 2294 patients were screened between 2004 and 2014 by ⁶⁸Ga somatostatin receptor (SSTR) PET/CT. Intention to treat analysis included 1048 patients, who received at least one cycle of ⁹⁰Yttrium or ¹⁷⁷Lutetium-based PRRT. Progression free survival was determined by ⁶⁸Ga SSTR-PET/CT and EORTC response criteria. Adverse events were determined by CTCAE criteria.

Results

Overall survival (95% confidence interval) of all patients was 51 months (47.0-54.9) and differed significantly according to radionuclide, grading, previous therapies, primary site and functionality. Progression free survival (based on PET/CT) of all patients was 19 months (16.9-21), which was significantly influenced by radionuclide, grading, and origin of neuroendocrine neoplasm. Progression free survival after initial progression and first and second resumption of PRRT after therapy-free intervals of more than 6 months were 11 months (9.4-12.5) and 8 months (6.4-9.5), respectively. Myelodysplastic syndrome or leukemia developed in 22 patients (2.1%) and 5 patients required hemodialysis after treatment, other adverse events were rare.

Conclusion

PRRT is effective and overall survival is favorable in patients with neuroendocrine neoplasms depending on the radionuclide used for therapy, grading and origin of the neuroendocrine neoplasm which is not exactly mirrored in progression free survival as determined by highly sensitive ⁶⁸Ga somatostatin receptor PET/CT using EORTC criteria for determining response to therapy.

Morphological and Functional Imaging for Detecting and Assessing the Resectability of Neuroendocrine Liver Metastases

This review evaluates the diagnostic efficacy of different morphological and functional imaging modalities (ultrasound [US], computed tomography [CT], magnetic resonance [MR] imaging, scintigraphy, and positron emission tomography [PET]) in detecting neuroendocrine liver metastases (NELM), assessing vascular and biliary involvement, and the presence of extrahepatic disease. MR imaging is superior for depicting NELM compared to US, CT, and somatostatin receptor scintigraphy. Diffusion-weighted MR imaging is more sensitive for detecting NELM than both T2-weighted and dynamic gadolinium-enhanced MR sequences, and should be systematically performed. Similarly, gadoxetic acid-enhanced MR imaging is more sensitive for detecting liver metastases than conventional extracellular gadolinium chelate-enhanced MR sequences. Its role in detecting NELM remains investigational but appears promising. Somatostatin receptor-targeted PET/CT is a highly effective approach in assessing the resectability of well-differentiated NELM due to very high specificity (and high sensitivity) and its ability to detect small volume extrahepatic disease; this molecular imaging modality is becoming increasingly available in and outside Europe after the recent approval of 6868-DOTATATE in the US. In addition, the information from multiphase, contrast-enhanced CT with 3D reconstruction - obtained concurrently with the information on somatostatin receptor expression of the metastases - is very helpful in planning the extent and type of resection of NELM.

Theranostics of Neuroendocrine Tumors

Somatostatin receptor positron emission tomography/computed tomography using ⁶⁸Ga-labeled somatostatin analogs is the mainstay for the evaluation of receptor status in neuroendocrine tumors (NETs). This translates towards better therapy options, with increasing evidence of peptide receptor radionuclide therapy (PRRT) as the treatment of choice for advanced or progressive NETs. There are benefits in progression-free and overall survival as well as a significant improvement in clinical condition. In patients with progressive NETs, fractionated, personalized PRRT results in good therapeutic responses with no significant severe hematological and/or renal toxicity, thus improving quality of life.

177Lu-3BP-227 for Neurotensin Receptor 1-Targeted Therapy of Metastatic Pancreatic Adenocarcinoma: First Clinical Results

Neurotensin receptor 1 (NTR1) is overexpressed in ductal pancreatic adenocarcinoma, which is still one of the deadliest cancers, with a very poor prognosis. Eligible patients were offered salvage radiopharmaceutical therapy with the novel NTR1 antagonist ¹⁷⁷Lu-3BP-227. Methods: Six patients with confirmed ductal pancreatic adenocarcinoma who had exhausted all other treatment options received ¹⁷⁷Lu-3BP-227 for evaluation of NTR1 expression in vivo. Three patients received treatment activities of 5.1-7.5 GBq. Results: Administration of ¹⁷⁷Lu-3BP-227 was well tolerated by all patients. The kidneys were identified as the dose-limiting organ. The most severe adverse event was reversible grade 2 anemia. One patient achieved a partial response and experienced significant improvement of symptoms and quality of life. This patient survived 13 mo from diagnosis and 11 mo from the start of ¹⁷⁷Lu-3BP-227 therapy. Conclusion: This initial report provides clinical evidence of the feasibility of treatment of ductal pancreatic adenocarcinoma using ¹⁷⁷Lu-3BP-227.

Abstract 944: Chemokine receptor signaling as a new tool to improve lung cancer diagnostics and therapy

Background: The tumor microenvironment plays a critical role in cancer development, progression, and control. We demonstrated in vitro and in vivo that a bidirectional crosstalk between tumor-associated macrophages and cancer cells via CCR2-CCL2 and CX3CR1-CXCL1 signaling is fundamental for lung cancer growth and metastasis offers new treatment concepts.

Aim: Our working hypothesis is to develop a new platform for specific chemokine receptor (CCR2) PET imaging and a range of theranostic applications in lung cancer. For this purpose, we planned to define the CCR2 expression in NSCLC as well as in SCLC, tumor cells as well as immune/inflammatory cells.

Material and Methods: This is a multicenter trial with patients from Zentralklinik Bad Berka GmbH (n =100 NSCLC, n=100 SCLC). All patients gave informed consent according to the declaration of Helsinki. FFPE material was available in all cases. CCR2 CXCR4 and CX3CR1 expression was determined by immunohistochemistry with the avidin-biotin-peroxidase-complex.

Results: Analyzing 96 NSCLC (47 adenocarcinoma, 49 squamous cell carcinoma) and 45 SCLC tumor samples, we found CXCR4 and CCR2 chemokine receptor expression in tumor, immune and inflammatory cells. In NSCLC, co-expression between CCR2 and CXCR4 staining was very high concerning their expression on tumor cells rising with higher tumor stages, proliferation rate and grading. CCR2 expression in immune cells was restricted to lower stages; the same pattern could be observed in 45 SCLC tumor samples where CCR2 expression on immune cells was found especially in limited disease rather than in metastatic disease; CXCR4 expression in tumor cells was found to be high in all stages of SCLC. To evaluate the therapeutic efficacy of CCR2 antagonism in vivo, we injected LLC1 s.c. into WT mice treated with CCR2 antagonist (RS504393) or vehicle. Notably, tumor growth was significantly inhibited in CCR2 antagonist-treated mice as compared with vehicle-treated mice.

Discussion: Our preliminary results show a significant portion of CCR2 positive tumors - NSCLC as well as SCLC which would qualify for a CCR2-based imaging as well as - demonstrated in our mice models - CCR2 inhibitory strategies. This should be evaluated in further preclinical trials.

Citation Format: Katalin Nagy-Major, Jörg Sänger, Harshad R. Kulkarni, Peter Fix, Almut Kunze, Amelie Lupp, Reiner Bonnet, Werner Seeger, Richard P. Baum, Patricia Grabowski, Rajkumar Savai. Chemokine receptor signaling as a new tool to improve lung cancer diagnostics and therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 944. doi:10.1158/1538-7445.AM2017-944

CEA, CA15.3 and 18-FDG PET in the follow-up of early breast cancer (BC) patients (pts): A prospective, multicentric, randomized trial—KRONOS patient-oriented new surveillance study Italy

TPS11627

Background: Current recommendations for breast cancer (BC) surveillance in asymptomatic patients (pts) include only mammography and physical examination and arise from two trials conducted in the 80’s. Since then new findings about BC biology, treatment and the introduction of cutting-edge diagnostic technologies such as 18-FDG PET have deeply modified our clinical scenarios. The aim of this prospective randomized trial is to verify if the serial measurement of CEA and CA15-3 followed by 18-FDG PET can anticipate the diagnosis of BC recurrence compared to control arm by estimation of the difference of restricted mean survival time (RMST) between the two arms. If the end-point will be met a subsequent extension trial will investigate the impact of the earlier diagnosis of distant metastases on survival. Methods: Pts diagnosed with stage I-III BC, who underwent adequate surgery are eligible. Special histologies and low-risk cases according to St. Gallen criteria are excluded. The study includes pts at the beginning of the follow-up after the conclusion of primary treatment (cohort 1), and pts that have concluded without relapse the first 5 years of follow-up (cohort 2). Eligible pts will be randomized in a 1:1 ratio to follow-up according to local practice (control arm) or to three-monthly serial dosing of CEA and CA15-3 and subsequent 18 FDG-PET only in case of an increase of CEA and/or CA 15.3 greater than a critical difference compared to baseline (experimental arm). The following stratification factors will be used: node negative vs positive, HER2 negative vs positive, ER positive vs negative. Eight-hundred pts will be enrolled over 3 years. For such a calculation, we made the assumption of a 20% baseline 5-year incidence of relapse. The target reduction of three months in RMST implies a median time of diagnostic anticipation, conditional on having BC recurrence, of 10 months. The follow-up will continue until 10 years from surgery. Since 23rd October 2014 573 pts have been enrolled. The present trial was approved by the Ethical Committee of each participating centre and is registered on Clinical trial information: NCT02261389.

Surgery in combination with peptide receptor radionuclide therapy is effective in metastatic neuroendocrine tumors and is definable by blood gene transcript analysis

e15697

Background: Neuroendocrine tumours (NET) of the pancreas (PNET) or small bowel (SBNET) frequently present with metastases at initial diagnosis, undermining the efficacy of surgical treatment. Peptide receptor radionuclide therapy (PRRT) with radiolabelled somatostatin analogues, 90Y-DOTATOC and 177Lu-DOTATATE, has been shown to achieve prolonged progression-free survival (PFS) in a substantial number of non-surgical patients with advanced NET. Our aim was to prospectively determine the efficacy of a combination of radical loco-regional surgery and PRRT in patients with metastasised NET. Methods: A set of inclusion criteria was defined (e.g. G1/G2 NET, initial tumour diagnosis, treatment naïve patient, stage IV NET, positivity on 68Ga DOTA- PET/CT, eligibility for surgery and PRRT). Patients underwent PRRT within 3 months following surgery. Follow-up included biochemistry and imaging. In a sub-cohort, blood-based neuroendocrine gene transcript analysis of 51 genes (NETest) was used to define the effectiveness of treatment. Outcome measures included 5-year overall survival (OS) and PFS from initial diagnosis. Results: Twenty-five patients (5 PNET, 20 SBNET) met eligibility criteria and were included. There were 13 men (52%) and mean age was 57.1 years. All patients with SB NET underwent right hemicolectomy, terminal ileal resection and mesenteric lympadenectomy. In all PNET patients only limited pancreatic resection was required. The median number of PRRT cycles was 4 (range 2-6). Post-treatment mortality was 0%. Surgical morbidity was 12% (all Clavien-Dindo grade 1). Transient grade 1 toxicity occurred post-PRRT in 40%. NETest scores were increased in 8 patients (100%) pre-operatively and decreased in all following treatment. NETest decreases correlated with diminished tumour volume (R2=0.37, p=0.02). Median follow-up was 48 months (range 12-72months). Five-year OS was 90% and 5-year PFS was 84.3%. Conclusions: Radical loco-regional surgery for primary tumours combined with PRRT provides a novel, highly efficacious approach in metastasised NET. The NETest accurately measures the effectiveness of treatment.

Blood measurements of neuroendocrine tumor (NET) transcripts and gene cluster analysis to predict efficacy of peptide radioreceptor therapy

4091

Background: Peptide receptor radionuclide therapy (PRRT) capitalizes on somatostatin receptor (SSR) overexpression on NETs to deliver targeted isotope therapy. Objective prediction of efficacy remains to be established. Functional imaging of SSR expression (SRE) is used as a predictor of efficacy. Biomarkers e.g. circulating CgA, are ineffective. Circulating NET transcript analysis (NETest) integrated with tumor grade provides a Predictive Quotient Index (PQI) of PRRT. We validated the utility of this PRRT complementary diagnostic in a prospective, blinded study. Methods: 177Lu-PRRT (29.1±2.2 GBq). NETs ( n= 35); with progressive disease (66%). Baseline evaluations: Clinical status, Grade (Ki67), SRE, CgA (NeoLisa, ULN > 108ng/ml), and NETest (qRT-PCR - multianalyte algorithmic analyses, ULN > 14%). PQI: “omic” NETest gene expression (regulating metabolism and growth factor signaling) mathematically combined with Ki67 index. PQI has two prediction outputs: “responder” (R) vs “non-responder” (NR). Disease control was by RECIST criteria (R vs NR). All samples were blinded. Statistics: Cox proportional multiple regression, Kaplan-Meier survival, & McNemar-test. Results: At restaging, the overall response (disease control rate) was 77%; median PFS not reached (follow-up 4-13 months). Histology: GI: 5; GII: 21; GIII 1; and lung: TC: 2; AC: 5. SRE was Grade 3 (80%). Baseline CgA was 1556±1454ng/ml (89% elevated) and NETest was 60±21% (100% elevated) respectively. Predictive accuracies of SRE, clinical status, CgA levels ( > 2ULN) and NETest ranged from 25-54% (not-significant). PQI was the only predictive marker by multivariate analysis ( p= 0.002). The PQI diagnostic was 92% concordant with outcome and significantly more accurate than all other markers (McNemar: p< 0.002). Cox-proportional modeling confirmed PQI utility (OR: 9.1, p< 0.004). K-MS analysis identified significantly different mPFS between R (not reached) and NR (9.3 months; HR: 8.3, p< 0.0005). Conclusions: A pre-PRRT analysis of circulating NET genes, the predictive quotient index comprising “omic” analysis and grading, is validated to predict the efficacy of PRRT therapy in GEP and lung NETs.

Novel Radiolabeled Bisphosphonates for PET Diagnosis and Endoradiotherapy of Bone Metastases

Bone metastases, often a consequence of breast, prostate, and lung carcinomas, are characterized by an increased bone turnover, which can be visualized by positron emission tomography (PET), as well as single-photon emission computed tomography (SPECT). Bisphosphonate complexes of ^99mTc are predominantly used as SPECT tracers. In contrast to SPECT, PET offers a higher spatial resolution and, owing to the ⁶⁸Ge/⁶⁸Ga generator, an analog to the established ^99mTc generator exists. Complexation of Ga(III) requires the use of chelators. Therefore, DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), NOTA (1,4,7-triazacyclododecane-1,4,7-triacetic acid), and their derivatives, are often used. The combination of these macrocyclic chelators and bisphosphonates is currently studied worldwide. The use of DOTA offers the possibility of a therapeutic application by complexing the β-emitter ¹⁷⁷Lu. This overview describes the possibility of diagnosing bone metastases using [⁶⁸Ga]Ga-BPAMD (⁶⁸Ga-labeled (4-{[bis-(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl)acetic acid) as well as the successful application of [¹⁷⁷Lu]Lu-BPAMD for therapy and the development of new diagnostic and therapeutic tools based on this structure. Improvements concerning both the chelator and the bisphosphonate structure are illustrated providing new ⁶⁸Ga- and ¹⁷⁷Lu-labeled bisphosphonates offering improved pharmacological properties.