Detecting and Locating the Site of Local Relapse Using 18F-PSMA-1007 Imaging After Primary Treatment of 135 Prostate Cancer Patients-Potential Impact on PSMA-Guided Radiation Therapy.

PURPOSE: Due to limited imaging options, the visualization of a local relapse of prostate cancer used to pose a considerable challenge. However, since the integration of 18F-PSMA-1007-PET/CT into the clinic, a relapsed tumor can now easily be detected by hybrid imaging. The present study aimed to evaluate and map the allocate relapse in a large cohort of prostate cancer patients focusing on individual patient management conclusions for radiation therapy. PROCEDURES: The current study included 135 men with prostate cancer after primary treatment who underwent 18F-PSMA-1007-PET/CT due to biochemical relapse detecting a local relapse. Imaging data were reassessed and analyzed with regard to relapse locations. For the correlation of tumor foci with clinical data, we used binary logistic regression models as well as the Kruskal-Wallis test and Mann-Whitney test. RESULTS: In total, 69.6% of all patients (mean age: 65 years) underwent prostatectomy while 30.4% underwent radiation therapy. PET imaging detected most frequently a unifocal relapse (72.6%). There was a statistically significantly higher rate of ipsilateral cases among the relapsed tumors. Comparing both treatment approaches, tumors relapsed most commonly within the posterior region after surgery and transition/peripheral zone after radiation therapy, respectively. CONCLUSIONS: The present study confirms that 18F-PSMA-1007-PET/CT is highly suitable for the localization and allocation of a local relapse in patients with prostate cancer. The data enable further optimizing dose prescriptions and target volume delineations of radiation therapy in the future.

Distinguishing Benign and Malignant Findings on [68 Ga]-FAPI PET/CT Based on Quantitative SUV Measurements.

AIM/PURPOSE: Fibroblast activation protein (FAP) is overexpressed by cancer-associated fibroblasts. However, activated fibroblasts have been shown to play a significant role also in certain benign conditions such as wound healing or chronic inflammation. Therefore, the current study aimed to identify whether FAPI uptake might differ between malignant lesions and benign conditions. MATERIAL AND METHODS: We retrospectively analyzed 155 patients with various cancer types who received [68 Ga]-FAPI-04/02-PET/CT between July 2017 and March 2020. SUVmax, SUVmean, and lesion-to-background ratios (LBR) of FAPI uptake were measured in benign processes compared to malignant lesions (primary and/or 2 exemplary metastases). In addition, receiver operating characteristic (ROC) curve analysis was conducted to compare the predictive capabilities of semiquantitative PET/CT parameters. Furthermore, the sensitivity, specificity, optimal cutoff value, and 95% confidence interval (CI) were determined for each parameter. RESULTS: Benign lesions exhibited significantly lower FAPI uptake compared to malignant lesions (mean SUVmax benign vs. malignant: 4.2 vs. 10.6; p < 0.001). In ROC analysis, cutoff values of these lesions (benign vs. malignant) were established based on SUVmax, SUVmean, and LBR. The SUVmax cutoff value for all lesions was 5.5 and the corresponding sensitivity, specificity, accuracy, and AUC were 78.8%, 85.1%, 82.0%, and 0.89%, respectively. CONCLUSION: Our aim was to systematically analyze the pattern of FAPI uptake in benign and malignant processes. This investigation demonstrates that FAPI uptake might be useful to differentiate malignant and benign findings due to different patho-physiological origins.

FAP imaging in rare cancer entities-first clinical experience in a broad spectrum of malignancies.

PURPOSE: 68 Ga-FAPI (fibroblast activation protein inhibitor) is a rapidly evolving and highly promising radiotracer for PET/CT imaging, presenting excellent results in a variety of tumor entities, particularly in epithelial carcinomas. This retrospective analysis sought to evaluate the potential and impact of FAPI-PET/CT in rare cancer diseases with respect to improvement in staging and therapy, based on tracer uptake in normal organs and tumors. MATERIAL AND METHODS: Fifty-five patients with rare tumor entities, defined by a prevalence of 1 person out of 2000 or less, received a 68 Ga-FAPI-PET/CT scan. Fourteen women and 41 men (median age 60) were included within the following subgroups: cancer of unknown primary (n = 10), head and neck cancer (n = 13), gastrointestinal and biliary-pancreatic cancer (n = 17), urinary tract cancer (n = 4), neuroendocrine cancer (n = 4), and others (n = 7). Tracer uptake was quantified by standardized uptake values SUVmax and SUVmean and the tumor-to-background ratio (TBR) was determined (SUVmax tumor/SUVmean organ). RESULTS: In 20 out of 55 patients, the primary tumor was identified and 31 patients presented metastases (n = 88), characterized by a high mean SUVmax in primary (10.1) and metastatic lesions (7.6). The highest uptake was observed in liver metastases (n = 6) with a mean SUVmax of 9.8 and a high TBR of 8.7, closely followed by peritoneal carcinomatosis (n = 16) presenting a mean SUVmax of 9.8 and an excellent TBR of 29.6. In terms of the included subgroups, the highest uptake regarding mean SUVmax was determined in gastrointestinal and biliary-pancreatic cancer with 9.8 followed closely by urinary tract cancer with 9.5 and head and neck cancer (9.1). CONCLUSION: Due to excellent tumor visualization and, thereby, sharp contrasts in terms of high TBRs in primary and metastatic lesions in different rare malignancies, 68 Ga-FAPI-PET/CT crystallizes as a powerful and valuable imaging tool, particularly with respect to epithelial carcinomas, and therefore an enhancement to standard diagnostics imaging methodologies. The realization of further and prospective studies is of large importance to confirm the potential of FAP imaging in oncology.

Novel FAP ligands enable improved imaging contrast in sarcoma patients due to FAPI-PET/CT.

PURPOSE: A high expression of fibroblast activation protein (FAP) was observed in multiple sarcomas, indicating an enormous potential for PET/CT using 68Ga-radiolabeled inhibitors of FAP (FAPI). Therefore, this retrospective study aimed to evaluate the role of the novel hybrid imaging probe for sarcomas as a first clinical evaluation. METHODS: A cohort of 15 patients underwent 68Ga-FAPI-PET/CT for staging or restaging. The acquisition of PET scans was performed 60 min after administration of 127 to 308 MBq of the tracer. The uptake of 68Ga-FAPI in malignant tissue as well as in healthy organs was quantified by standardized uptake values SUVmean and SUVmax. RESULTS: Excellent tumor-to-background ratios (> 7) could be achieved due to low background activity and high SUVmax in primary tumors (median 7.16), local relapses (median 11.47), and metastases (median 6.29). The highest uptake was found for liposarcomas and high-grade disease (range 18.86-33.61). A high SUVmax (> 10) was observed for clinically more aggressive disease. CONCLUSION: These preliminary findings suggest a high potential for the clinical use of 68Ga-FAPI-PET/CT for patients diagnosed with sarcoma.

Impact of Primary Staging with Fibroblast Activation Protein Specific Enzyme Inhibitor (FAPI)-PET/CT on Radio-Oncologic Treatment Planning of Patients with Esophageal Cancer.

PURPOSE: Quinoline-based ligands targeting cancer-associated fibroblasts have emerged as promising radiopharmaceuticals in different tumor entities. The aim of this retrospective study was to explore the potential of FAPI-PET/CT in the initial staging of esophageal cancer patients and its usefulness in radiotherapy planning as a first clinical analysis. METHODS: Seven patients with treatment-naive esophageal cancer underwent FAPI-PET/CT. Tracer uptake was quantified by standardized uptake values (SUV)max and (SUV)mean. Six patients received definitive and one neoadjuvant (chemo)radiation therapy. Endo-esophageal clipping, the gold standard to define tumor margins not delineable per CT, was performed in three patients. RESULTS: Primary tumors demonstrated high FAPI uptake with a median SUVmax of 17.2. Excellent tumor-to-background ratios resulted in accurate target volume delineation and were found in perfect match with clipping. Detection of regional lymph node metastases facilitated the use of simultaneous integrated boost radiotherapy plans for these patients. CONCLUSION: FAPI-PET/CT may be beneficial for the management of esophageal cancer particularly in planning radiotherapy, but further research is necessary to increase patient number and statistical reliability.

PD-1 blockade: a therapeutic option for treatment of metastatic Merkel cell carcinoma.

The immune system is extremely important in the development and progression of Merkel cell carcinoma (MCC). Immune checkpoint blockade has recently been shown to enable efficacious treatment of a variety of tumours. We report the use of an anti-programmed death receptor 1 (PD-1) antibody for treatment of a patient with metastatic MCC. An 80-year-old patient with metastatic MCC received off-label treatment with the anti-PD-1 antibody pembrolizumab after the disease had progressed during therapy with oral etoposide. A positron emission tomography (PET) computed tomography scan performed after three cycles of pembrolizumab revealed responses to therapy with reduced size of the adrenal gland metastases and less PET activity in the adrenal gland and lymph node metastases. Treatment was resumed owing to disease progression after a treatment-free interval of > 4 months. During subsequent months of treatment, the size of the metastases stabilized and uptake of nuclide by all tumour sites once again decreased. These results reveal the potential efficacy of an anti-PD-1 antibody for treatment of metastatic MCC. Thus, they contribute to currently limited data on the use of anti-PD-1 antibodies for the treatment of MCC. Moreover, this is the first report of successful resumption of treatment of metastatic MCC with an anti-PD-1 antibody. Results from ongoing trials will contribute to determination of the relevance of PD-1 blockade in metastatic MCC.

[Significance of PSMA imaging in prostate cancer]. / Stellenwert der PSMA-Liganden-Bildgebung beim Prostatakarzinom.

BACKGROUND: Prostate cancer (PCa) is one of the most common malignancies of men in developed countries. To improve clinical diagnostics of PCa, 68Ga-PSMA-11 was recently introduced as a new PET tracer. 68Ga-PSMA-11 is able to specifically bind to the prostate-specific membrane antigen (PSMA), which is upregulated on the surface of prostate cancer cells in most patients. OBJECTIVES: To analyse the current significance of 68Ga-PSMA-11 PET imaging in prostate cancer in relation to staging of men with initial diagnosis, biochemical recurrence and metastatic disease. MATERIALS AND METHODS: Retrospective analysis of current literature (PubMed search) regarding 68Ga-PSMA-11 PET diagnostics in primary staging, in biochemical recurrence and in metastasized disease. RESULTS: Compared to conventional imaging, 68Ga-PSMA-11 PET/CT reaches a higher sensitivity with an excellent specificity in the clinical diagnosis of primary staging as well as staging for recurrence and advanced, metastasized disease. In biochemical recurrence, 68Ga-PSMA-11 PET/CT shows significantly higher detection rates in comparison to choline PET/CT, especially in patients with low PSA values. In the clinical diagnosis of recurrent disease, therapy concepts were changed in more than a quarter of the patients due to the use of 68Ga-PSMA-11 PET/CT. The significance of staging with 68Ga-PSMA-11 PET/CT in advanced metastasized patients remains uncertain. CONCLUSIONS: Due to the excellent results of 68Ga-PSMA-11 PET imaging, even in patients with slightly elevated PSA levels, it will continue to play an important role in clinical diagnostics of prostate cancer and, thus, its clinical utilization will become more widely spread.

[PSMA-targeted radioligand therapy in prostate cancer]. / Radionuklidtherapie des Prostatakarzinoms mittels PSMA-Lutetium.

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

F-18 labelled PSMA-1007: biodistribution, radiation dosimetry and histopathological validation of tumor lesions in prostate cancer patients.

PURPOSE: The prostate-specific membrane antigen (PSMA) targeted positron-emitting-tomography (PET) tracer 68Ga-PSMA-11 shows great promise in the detection of prostate cancer. However, 68Ga has several shortcomings as a radiolabel including short half-life and non-ideal energies, and this has motivated consideration of 18F-labelled analogs. 18F-PSMA-1007 was selected among several 18F-PSMA-ligand candidate compounds because it demonstrated high labelling yields, outstanding tumor uptake and fast, non-urinary background clearance. Here, we describe the properties of 18F-PSMA-1007 in human volunteers and patients. METHODS: Radiation dosimetry of 18F-PSMA-1007 was determined in three healthy volunteers who underwent whole-body PET-scans and concomitant blood and urine sampling. Following this, ten patients with high-risk prostate cancer underwent 18F-PSMA-1007 PET/CT (1 h and 3 h p.i.) and normal organ biodistribution and tumor uptakes were examined. Eight patients underwent prostatectomy with extended pelvic lymphadenectomy. Uptake in intra-prostatic lesions and lymph node metastases were correlated with final histopathology, including PSMA immunostaining. RESULTS: With an effective dose of approximately 4.4-5.5 mSv per 200-250 MBq examination, 18F-PSMA-1007 behaves similar to other PSMA-PET agents as well as to other 18F-labelled PET-tracers. In comparison to other PSMA-targeting PET-tracers, 18F-PSMA-1007 has reduced urinary clearance enabling excellent assessment of the prostate. Similar to 18F-DCFPyL and with slightly slower clearance kinetics than PSMA-11, favorable tumor-to-background ratios are observed 2-3 h after injection. In eight patients, diagnostic findings were successfully validated by histopathology. 18F-PSMA-1007 PET/CT detected 18 of 19 lymph node metastases in the pelvis, including nodes as small as 1 mm in diameter. CONCLUSION: 18F-PSMA-1007 performs at least comparably to 68Ga-PSMA-11, but its longer half-life combined with its superior energy characteristics and non-urinary excretion overcomes some practical limitations of 68Ga-labelled PSMA-targeted tracers.

Intra-individual comparison of (68)Ga-PSMA-11-PET/CT and multi-parametric MR for imaging of primary prostate cancer.

PURPOSE: Multi-parametric magnetic resonance imaging (MP-MRI) is currently the most comprehensive work up for non-invasive primary tumor staging of prostate cancer (PCa). Prostate-specific membrane antigen (PSMA)-Positron emission tomography-computed tomography (PET/CT) is presented to be a highly promising new technique for N- and M-staging in recurrent PCa-patients. The actual investigation analyses the potential of (68)Ga-PSMA11-PET/CT to assess the extent of primary prostate cancer by intra-individual comparison to MP-MRI. METHODS: In a retrospective study, ten patients with primary PCa underwent MP-MRI and PSMA-PET/CT for initial staging. All tumors were proven histopathological by biopsy. Image analysis was done in a quantitative (SUVmax) and qualitative (blinded read) fashion based on PI-RADS. The PI-RADS schema was then translated into a 3D-matrix and the euclidian distance of this coordinate system was used to quantify the extend of agreement. RESULTS: Both MP-MRI and PSMA-PET/CT presented a good allocation of the PCa, which was also in concordance to the tumor location validated in eight-segment resolution by biopsy. An Isocontour of 50 % SUVmax in PSMA-PET resulted in visually concordant tumor extension in comparison to MP-MRI (T2w and DWI). For 89.4 % of sections containing a tumor according to MP-MRI, the tumor was also identified in total or near-total agreement (euclidian distance ≤1) by PSMA-PET. Vice versa for 96.8 % of the sections identified as tumor bearing by PSMA-PET the tumor was also found in total or near-total agreement by MP-MRI. CONCLUSIONS: PSMA-PET/CT and MP-MRI correlated well with regard to tumor allocation in patients with a high pre-test probability for large tumors. Further research will be needed to evaluate its value in challenging situation such as prostatitis or after repeated negative biopsies.

PSMA PET/CT with Glu-urea-Lys-(Ahx)-[68Ga(HBED-CC)] versus 3D CT volumetric lymph node assessment in recurrent prostate cancer.

PURPOSE: PET/CT with the PSMA ligand is a powerful new method for the early detection of nodal metastases in patients with biochemical relapse. The purpose of this retrospective investigation was to evaluate the volume and dimensions of nodes identified by Glu-urea-Lys-(Ahx)-[(68)Ga(HBED-CC)] ((68)Ga-PSMA-11) in the setting of recurrent prostate cancer. METHODS: All PET/CT images were acquired 60 ± 10 min after intravenous injection of (68)Ga-PSMA-11 (mean dose 176 MBq). In 21 patients with recurrent prostate cancer and rising PSA, 49 PSMA-positive lymph nodes were identified. Using semiautomated lymph node segmentation software, node volume and short-axis and long-axis dimensions were measured and compared with the maximum standardized uptake values (SUVmax). Round nodes greater than or equal to 8 mm were considered positive by morphological criteria alone. The percentage of nodes identified by elevated SUVmax but not by conventional morphological criteria was determined. RESULTS: The mean volume of (68)Ga-PSMA-11-positive nodes was 0.5 ml (range 0.2 - 2.3 ml), and the mean short-axis diameter was 5.8 mm (range 2.4 - 13.3 mm). In 7 patients (33.3 %) with 31 PSMA-positive nodes only 11 (36 %) were morphologically positive based on diameters >8 mm on CT. In the remaining 14 patients (66.7 %), 18 (37 %) of PSMA positive lymph nodes had short-axis diameters <8 mm with a mean short-axis diameter of 5.0 mm (range 2.4 - 7.9 mm). Thus, in this population, (68)Ga-PSMA-11 PET/CT detected nodal recurrence in two-thirds of patients who would have been missed using conventional morphological criteria. CONCLUSION: (68)Ga-PSMA-11 PET/CT is more sensitive than CT based 3D volumetric lymph node evaluation in determining the node status of patients with recurrent prostate cancer, and is a promising method of restaging prostate cancers in this setting.

SUV of [68Ga]DOTATOC-PET/CT Predicts Response Probability of PRRT in Neuroendocrine Tumors.

PURPOSE: The goal of our study was to quantify the expression of the somatostatin receptors (SSTR2) using the maximum standardized uptake value (SUVmax) of [(68)Ga]DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTATOC) positron emission tomography (PET)-computed tomography (CT) in liver metastases of patients with neuroendocrine tumors (NETs) prior to peptide receptor radiation therapy (PRRT) and compare the initial tumor uptake with the final treatment outcome. PROCEDURES: SSTR2 expression of the 60 liver metastases in 30 NET patients was assessed at baseline and after PRRT by measuring SUVmax, tumor to spleen ratio (T/S ratio), and tumor to liver ratio (T/L ratio). Based on morphological changes and tumor size measured at baseline and follow-up contrast-enhanced CT (after three cycles of PRRT), lesions were divided into two groups by the following: (i) responding (n = 40) and (ii) non-responding (n = 20). RESULTS: Statistically significant differences were observed in the mean SUVmax for non-responding vs. responding lesions at baseline (18.00 ± 3.59 vs. 33.55 ± 4.62, p < 0.05) and for the mean T/S ratio (1.20 ± 0.37 vs. 1.90 ± 0.45, p < 0.05) and the mean T/L ratio (3.15 ± 0.53 vs. 4.97 ± 0.62, p < 0.05). Using the receiver operating characteristic curves, SUVmax was found a better metric than both T/L ratio and T/S ratio (area under the curve (AUC) of SUVmax 0.87; T/L ratio 0.78; T/S ratio 0.73) as a stratification criterion. Using a threshold value of >16.4 for SUVmax, the sensitivity and specificity in predicting responding lesions were 95 and 60 %, respectively. CONCLUSION: We propose a SUVmax cutoff of >16.4 from [(68)Ga]DOTATOC-PET-CT to select patients for PRRT. A T/L ratio >2.2 might present a scanner-independent criterion that enables the translation of our results to other institutions. However, the robustness of this arbitrary unit still needs to be evaluated with different PET scanners.

Comparison of 68Ga-DOTATOC biodistribution in patients with and without spleenectomy.

AIM: Ga-68 labeled somatostatin analogues such as 68Ga-DOTA0-Phe1-Tyr3-octrotide (DOTATOC) as PET tracers, have significantly improved the imaging of somatostatin receptors (SSTRs) expressing tumors. Due to unspecific parenchymal binding and the expression of SSTRs on leukocytes in the spleen this is the organ with the highest non-tumor uptake of DOTATOC. Therefore, we investigated the potential changes of normal tissue distribution and tumor concentration in patients with neuroendocrine tumors (NETs) with or without spleenectomy. METHODS: Out of 420 patients with pancreatic NET undergoing 68GA-DOTATOC PET/CT eleven patients with and eleven patients without spleenectomy were derived and matched in regard to tumor histology, tumor load, age and gender. The SUV(max) of liver metastases as well as of the following normal tissues was determined: pituitary gland, thyroid gland, liver parenchyma, kidneys and suprarenal glands. RESULTS: SUV(max) values with and without spleenectomy were: in the liver metastasis (19.17 ± 6.05 versus 37.67 ± 16.31), in the thyroid gland (2.56 ± 1.33 versus 2.66 ± 0.94), in the pituitary gland (4.08 ± 1.79 versus 4.92 ± 1.93) in suprarenal glands (7.18 ± 3.33 versus 9.73 ± 3.46 on the left side and 7.32 ± 3.03 versus 11.19 ± 5.72 on the right side), in the kidneys (8.1 3 ± 4.26 on the left side and 8.11 ± 4.16 on the right side versus 8.62 ± 2.17 on the left side and 9.79 ± 2.18 on the right side) and in normal liver tissue (5.74 ± 1.55 versus 6.22 ± 1.95). The difference was statistically significant (Wilcoxon test P<0.05) in tumor lesions, adrenal and kidney tissue. CONCLUSION: Spleenectomy must be considered as a relevant factor when reporting the outcome of SSTR targeted diagnostics and therapies.

[Radionuclide therapy of endocrine-related cancer]. / Nuklearmedizinische Therapie endokriner Tumoren.

This article gives an overview of the established radionuclide therapies for endocrine-related cancer that already have market authorization or are currently under evaluation in clinical trials. Radioiodine therapy is still the gold standard for differentiated iodine-avid thyroid cancer. In patients with bone and lung metastases (near) total remission is seen in approximately 50% and the 15-year survival rate for these patients is approximately 90%. In contrast to the USA, meta-iodobenzylguanidine (MIBG) therapy has market approval in Europe. According to the current literature, in the setting of advanced stage neuroblastoma and malignant pheochromocytoma or paraganglioma, radiological remission can be achieved in >30% and symptom control in almost 80% of the treated patients. Somatostatin receptor targeted radionuclide therapies (e.g. with DOTATATE or DOTATOC) demonstrated promising results in phase 2 trials, reporting progression-free survival in the range of 24-36 months. A first phase 3 pivotal trial for intestinal carcinoids is currently recruiting and another trial for pancreatic neuroendocrine tumors is planned. Radiopharmaceuticals based on glucagon-like peptide 1 (GLP1) or minigastrins are in the early evaluation stage for application in the treatment of insulinomas and medullary thyroid cancer. In general, radiopharmaceutical therapy belongs to the group of so-called theranostics which means that therapy is tailored for individual patients based on molecular imaging diagnostics to stratify target positive or target negative tumor phenotypes.

²¹³Bi-DOTATOC receptor-targeted alpha-radionuclide therapy induces remission in neuroendocrine tumours refractory to beta radiation: a first-in-human experience.

PURPOSE: Radiopeptide therapy using a somatostatin analogue labelled with a beta emitter such as (90)Y/(177)Lu-DOTATOC is a new therapeutic option in neuroendocrine cancer. Alternative treatments for patients with refractory disease are rare. Here we report the first-in-human experience with (213)Bi-DOTATOC targeted alpha therapy (TAT) in patients pretreated with beta emitters. METHODS: Seven patients with progressive advanced neuroendocrine liver metastases refractory to treatment with (90)Y/(177)Lu-DOTATOC were treated with an intraarterial infusion of (213)Bi-DOTATOC, and one patient with bone marrow carcinosis was treated with a systemic infusion of (213)Bi-DOTATOC. Haematological, kidney and endocrine toxicities were assessed according to CTCAE criteria. Radiological response was assessed with contrast-enhanced MRI and (68)Ga-DOTATOC-PET/CT. More than 2 years of follow-up were available in seven patients. RESULTS: The biodistribution of (213)Bi-DOTATOC was evaluable with 440 keV gamma emission scans, and demonstrated specific tumour binding. Enduring responses were observed in all treated patients. Chronic kidney toxicity was moderate. Acute haematotoxicity was even less pronounced than with the preceding beta therapies. CONCLUSION: TAT can induce remission of tumours refractory to beta radiation with favourable acute and mid-term toxicity at therapeutic effective doses.

[Importance of nuclear medicine diagnostics in CUP syndrome]. / Stellenwert der nuklearmedizinischen Diagnostik bei CUP-Syndrom.

CLINICAL/METHODICAL ISSUE: The diagnostic work-up in patients with carcinoma of unknown primary (CUP) syndrome is extensive, highly time-consuming and cost-intensive and ultimately often fails to detect a primary site. STANDARD RADIOLOGICAL METHODS: In this context chest X-ray and computed tomography (CT) have been used as standard imaging modalities in CUP syndrome. METHODOLOGICAL INNOVATIONS: Since the introduction of positron emission tomography (PET) evaluation of tumor vitality has become possible. Furthermore, PET-CT hybrid scanners allow the combination of functional and morphological imaging. PERFORMANCE: Several meta-analyses have reported an additional overall detection rate between 24.5 % and 44 % by either PET or PET-CT. Metastatic localization (cervical versus extracervical) did not influence the performance. The sensitivity was usually high (> 80 %) but specificity was moderate ranging from 68 % to 88 % at best. If mentioned, the results obtained by fluorodeoxyglucose (FDG)-PET significantly changed the clinical management in approximately one third of the patients studied. In a direct comparison with PET alone, PET-CT did not depict significantly more primary tumors but was able to reduce false positive findings. ACHIEVEMENTS: To determine the real additional value of PET-CT in the diagnosis of CUP syndrome large prospective studies with more uniform inclusion criteria are needed. Despite the capabilities of FDG-PET-CT there is as yet no evidence that a potentially improved diagnostic algorithm is translated into a better patient outcome. PRACTICAL RECOMMENDATIONS: Nevertheless, FDG-PET-CT should be performed in all CUP patients where conventional imaging failed to detect a primary site or the results are equivocal. In CUP patients with cervical lymph node metastases PET-CT should be carried out prior to panendoscopy to reduce the number of false negative biopsies.

Contrast-enhanced ultrasound monitoring of perfusion changes in hepatic neuroendocrine metastases after systemic versus selective arterial 177Lu/90Y-DOTATOC and 213Bi-DOTATOC radiopeptide therapy.

AIM: Radiopeptide therapy with beta emitter labeled (177)Lu/(90)Y- DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTATOC) and more recently also alpha emitting (213)Bi-DOTATOC are promising new treatments for neuroendocrine tumors. No early predictors for treatment response have been recognized and tumor-shrinkage after radiation therapy appears slowly. In some solid tumors a decline in tumor perfusion was found predictive of final treatment response but the gold standard multiphase computed tomography (CT) has a high radiation burden. Therefore we evaluated the ability of contrast-enhanced ultrasound (CEUS) to evaluate tumor perfusion as a response criteria. MATERIALS AND METHODS: 14 patients with hepatic neuroendocrine tumor (NET) metastases were enrolled in the retrospective study. Eleven patients were treated with beta-emitting (177)Lu/(90)Y-DOTATOC, either intravenous (i.v.) (n = 5) or intra-arterial (i.a.) (n = 6) and three patients received alpha-emitting (213)Bi-DOTATOC (i.a.). CEUS and contrast-enhanced CT (CE-CT) were performed before and 3 months after treatment. RESULTS: CE-CT and CEUS presented comparable results in the baseline study and in the assessment of perfusion changes due to the different treatment regimes. A therapy related decrease in tumor perfusion is an early predictor of longterm morphologic response. CONCLUSION: CEUS is available and radiation free technique which showed comparable results for perfusion and diameter of liver metastases compared to CE-CT. Intensity reduction in an arterial phase CEUS can be seen as a positive sign indicating long term tumor response to treatment. Therefore CEUS may be considered as an imaging modality for monitoring early treatment after focal alpha and beta targeted therapy.

Impact of peptide receptor radionuclide therapy on the 68Ga-DOTATOC-PET/CT uptake in normal tissue.

AIM: Positron-emission tomography/computed tomography (PET/CT) with [68Ga]DOTA0-Phe1-Tyr3-octreotide (68Ga-DOTA-TOC) became a standard for somatostatin receptor imaging. We investigated the potential changes of normal tissue uptake in patients with neuroendocrine tumor undergoing peptide receptor radionuclide therapy (PRRT). METHODS: Sixteen patients underwent [68Ga]-DOTA-TOC-PET/CT prior and after 4-6 cycles of PRRT (mean administered activity: 13.8 GBq 90Y+ 9.6 177Lu). The maximum standardized uptake values (SUVmax) of pituitary, thyroid, spleen, liver parenchyma, pancreas, kidneys and adrenals were determined, respectively. RESULTS: SUVmax values prior and after PRRT were in pituitary (5, 56±2,91/ 4,47±2,53), thyroid (2.05±1.11/ 2.49±2.47), spleen (24.95±14.20/20.06±8.53), liver (7.13±3.96/6.62±2.63), pancreas (6.96±1.99/6.83±2.00), kidneys (13.0±3.85/11.31±3.31) and adrenals (9.65± 4.20/7.10±2.86). A comparison of pre- and post treatment values revealed no significant differences (P>0.05) in any of these organs. CONCLUSION: The uptake of [68Ga] DOTA-TOC in normal tissue is not significantly affected by PRRT. This is relevant with regards to therapeutic monitoring were tumor-to-non-tumor ratio seems to be the most robust biomarker.

Protective embolization of the gastroduodenal artery with a one-HydroCoil technique in radioembolization procedures.

PURPOSE: Protective occlusion of the gastroduodenal artery (GDA) is required to avoid severe adverse effects and complications in radioembolization procedures. Because of the expandable features of HydroCoils, our goal was to occlude the GDA with only one HydroCoil to provide particle reflux protection. METHODS: Twenty-three subjects with unresectable liver tumors, who were scheduled for protective occlusion of the GDA before radioembolization therapy, were included. The primary end point was to achieve a proximal occlusion of the GDA with only one detachable HydroCoil. Evaluated parameters were duration of deployment, and early (during the intervention) and late (7-21 days) occlusion rates of GDA. Secondary end points included complete duration of the intervention, amount of contrast medium used, fluoroscopy rates, and adverse effects. RESULTS: In all cases, the GDA was successfully occluded with only one HydroCoil. The selected diameter/length range was 4/10 mm in 2 patients, 4/15 mm in 6 patients, and 4/20 mm in 15 patients. HydroCoils were implanted, on average, 3.75 mm from the origin of the GDA (range 1.5-6.8 mm), with an average deployment time of 2:47 (median 2:42, range 2:30-3:07) min. In 21 (91%) of 23 patients, a complete occlusion of the GDA was achieved during the first 30 min after the coil implantation; however, in all patients, a late occlusion of the GDA was present after 6 to 29 days. No clinical or technical complications were reported. CONCLUSION: We demonstrated that occlusion of the GDA with a single HydroCoil is a safe procedure and successfully prevents extrahepatic embolization before radioembolization.