12:46 CET
108 - Clinical Oncology - Rapid Fire Session: Prostate - BCR and More
Clinical Oncology
Sunday, October 13, 08:00 - 09:30
Type of session: Clinical Oncology Track
Topic: Clinical Oncology
Sub topic: 709 Urogenital
Chairpersons: M. Eiber (GERMANY/DE), C. Nanni (Bologna/IT)

12 presentations in this session:
Impact of application of furosemide combined with hydration on the halo artefact and intensity of tracer accumulation in the urinary bladder in 68Ga PSMA-11 PET/CT
C. Uprimny1, A. Kroiss2, B. Nilica2, H. Svirydenka2, E. Elmisgheri2, C. Decristoforo2, E. Guggenberg2, G. di Santo2, I. Virgolini2;
1Medical University of Innsbruck, Gaimberg, AUSTRIA, 2Medical University of Innsbruck, Innsbruck, AUSTRIA.

Aim/Introduction: Comparative study to assess systematically the influence of hydration and application of furosemide on the occurence of the halo artefact, a photopenic artefact surrounding the urinary bladder, that might be present on 68Ga-PSMA-11 PET/CT images. Materials and Methods: 200 consecutive prostate cancer patients referred for 68Ga-PSMA-11 PET/CT were included. Four groups receiving different preparation prior to imaging, comprising 50 patients each, were compared. Group one: no intervention. Group two: intravenous hydration with 500 ml sodium chloride after tracer application. Group three: intravenous hydration with 500 ml sodium chloride and 20 mg furosemide injected after tracer application. Group four: intravenous hydration with 500 ml sodium chloride and 40 mg furosemide injected after tracer application. Images were analysed visually to judge whether halo artefact was present. In addition intensity of tracer uptake in the urinary bladder was measured semiquantitatively with calculation of maximum standardised uptake value (SUVmax). Results: In group one (no preparation) ten patients (20 %) demonstrated a halo artefact surrounding the urinary bladder with a median SUVmax of 66.9 (range: 9.3 - 349.9) of the urinary bladder. In group two (intravenous hydration only) in seven patients (14 %) the halo artefact was present with a median SUVmax of 21.8 (range: 9.0 - 170.6) in the urinary bladder. In group three (20 mg furosemide) and group four (40 mg furosemide) no halo artefact could be found. Median SUVmax of the urinary bladder in group three and four was 8.9 (range: 2.3 - 32.1) and 9.7 (range: 2.3 - 26.8), respectively. The difference in number of halo artefact and median SUVmax of urinary bladder between group one and group three and four was statistically significant (p <0.001). Although median SUVmax was significantly reduced between group one and two, number of halo artefact in these two groups did not differ significantly. No significant difference of results could be observed in patients receiving 20 mg furosemide and those injected with 40 mg furosemide. Conclusion: Intravenous injection of 20 mg furosemide combined with 500 ml sodium chloride significantly reduces the halo artefact and median SUVmax of the urinary bladder in 68Ga-PSMA-11 PET/CT in comparison to patients receiving no preparation and patients receiving only hydration with 500 ml sodium chloride. References: none

Next-generation PET is a sensitive and reproducible biomarker of early CRPC
M. M. Weber1, C. E. Kurek2, F. Barbato1, C. Rischpler1, M. Eiber3, T. Maurer4, B. Hadaschik5, K. G. Herrmann1, A. Wetter6, F. P. Wolfgang1;
1University Clinic Essen, Department of Nuclear medicine, Essen, GERMANY, 2University Clinic Essen, Deparment of Nuclear medicine, Essen, GERMANY, 3Department of Nuclear Medicine, Klinikum Rechts der Isar, Technische Universität München, Munich, GERMANY, 4Martini-Clinic and Department of Urology, University Clinic Hamburg-Eppendorf (UKE), Hamburg, GERMANY, 5Department of Urology; University Hospital Essen, Essen, GERMANY, 6Institute of Diagnostic and Interventional Radiology and Neuroradiology; University Hospital Essen, Essen, GERMANY.

Aim/Introduction: At early diagnosis of castration-resistant prostate cancer (CRPC), PSA measurement is limited by fluctuations and conventional imaging by low detection probability. We thus aim to assess the value of PSMA-PET/CT as biomarker at early CRPC. Materials and Methods: We screened our local database (n=1369) for patients with histopathologically proven prostate cancer, rising PSA despite effective androgen-deprivation therapy and PSA ≤ 3. CT and PSMA-PET/CT scans of eligible patients (n=46) were anonymized and interpreted independently by three blinded readers. Patients were stratified by PSA (<1.0; 1-0-2.0; 2.0-3.0); primary endpoint was the per-patient detection rate. Secondary endpoints were the per-region detection rate, interobserver agreement and risk factors for PET positivity or M1-disease.
Results: PSMA-PET/CT was positive in 74% of patients. 28% patients had local disease only, 46% patients had M1-disease (26% bone, 4% visceral). Interobserver agreement was substantial/almost perfect (Fleiss’ kappa 0.80, 95% confidence interval 0.63-0.97) for PET. Factors typically associated with adverse outcome (e.g. Gleason Score ≥8, PSA doubling time≤6 months) were not associated with PET positivity or M1-disease. Conclusion: PSMA-PET/CT localizes prostate cancer in more than two thirds of patients with pre/early CRPC, even before PSA exceeds the 2 ng/mL threshold. PSMA-PET/CT is a sensitive and reproducible biomarker of disease that may allow earlier diagnosis and guided treatment of CRPC. References: none

Benefit of CT urography in 68Ga-PSMA-11 PET with low dose CT
F. Rosar1, M. Hügle1, M. Ries1, S. Maus1, M. Bartholomä1, T. Stemler1, H. Bohnenberger1, P. Fries2, F. Khreish1, S. Ezziddin1;
1Department of Nuclear Medicine, Saarland University Medical Center, Homburg, GERMANY, 2Department of Radiology, Saarland University Medical Center, Homburg, GERMANY.

Aim/Introduction: Accuracy of 68Ga-PSMA-11 PET/CT may be hampered by ureter accumulation. Depending on localization and configuration it may mimic lymph node metastases. We evaluated the benefit of intravenous CT contrast agent for urography in 68Ga-PSMA-11 PET with low dose CT to help to differentiate between lymph node metastasis and urinary tract activity.
Materials and Methods: Retrospective analysis of n=247 PET/CT scans (Biograph 40 mCT, 124±17 MBq 68Ga-PSMA-11, 60 min p.i. image-acquisition, iterative 3D OSEM algorithm (3 iterations, 24 subsets), low dose CT (120 keV, max. 30 mAs)) for primary staging, biochemical recurrence or local therapy planning. For urography, a reduced amount of 30 ml contrast agent (370-400 mg iodine/ml) was applied 10 minutes prior to image acquisition. All foci of potential pathologic radiotracer accumulation were reviewed and analysed. The success of achieving a contrasted ureter was verified by measuring Hounsfield units in the ureter. All foci were rated and scored by at least three experienced physicians to assess the provided benefit of urography. In addition, the imaging outcome for further decision making was evaluated.
Results: By CT urography, it was possible to identify each ureter on low dose CT, with its major part contrasted. In 120/247 PET/CT scans (48.6 %) with 189 sites of (peri)ureteral accumulation urography increased the diagnostic confidence. In 60 (24.3 %) scans, urography was rated important for decision making. In 36 of 189 sites, the tracer accumulation would not have been attributable to lymph node metastases or ureter excretion without urography. In 42 (17.0 %) scans, urography-enhanced PET-CT reading was clinically relevant (up-/downstaging) with potential impact on subsequent patient care. In 30 of these 42 cases (12.1 % of all), change in treatment would have resulted from misdiagnosed focus without urography.
Conclusion: Additional administered contrast agent for CT-urography benefits the interpretation of 68Ga-PSMA-11 PET with low dose CT by increasing diagnostic confidence in the differentiation of lymph node metastases and urinary tract activity. A subsequent change in patient management will result in a small but significant subset (12% in our cohort). Reduced contrast amount of 30 ml (370-400 mg iodine/ml) applied 10 minutes prior to image acquisition is adequate to identify the ureter on low dose CT. References: none

Prospective intra-patient comparison of 18F-Fluciclovine and 68Ga-PSMA-11 PET/CT in biochemical recurrence of prostate cancer after definitive therapy
B. Pernthaler, H. Kvaternik, R. Kulnik, C. Gstettner, R. M. Aigner;
Medical University Graz, Department of Radiology, Division of Nuclear Medicine, Graz, AUSTRIA.

Aim/Introduction: To compare 18F-Fluciclovine to 68Ga-PSMA-11 PET/CT in patients with biochemical recurrence of prostate cancer. To evaluate the advantages, disadvantages and comparability of these PET tracers. Materials and Methods: Prospective study of 58 patients with biochemical recurrence of prostate cancer after definitive primary therapy (radical prostatectomy, radiation therapy). 18F-Fluciclovine and 68Ga-PSMA-11 PET/CT were performed within a time window of median 9,4 days with standardized image acquisition protocols and interpretation criteria. The performance of both tracers were evaluated on a patient- and region-based analysis. Results: The patient-level detection rate for prostate cancer recurrence was 79.3% in 18F-Fluciclovine and 82.8% in 68Ga-PSMA-11 (p=0.64). Local recurrence was detected in 22/58 (37.9%) patients on 18F-Fluciclovine PET/CT and only in 16/58 patients (27.6%) on 68Ga-PSMA-11 PET/CT (p=0.03). In 6/58 patients (10.4%) local recurrence could only be detected in 18F-Fluciclovine scans. Local pelvic lymph node recurrence was detected in 27/58 patients (46.6%) on 18F-Fluciclovine PET/CT and in 29/58 patients (50.0%) on 68Ga-PSMA-11 PET/CT (p=0.71). Local pelvic lymph node recurrence was only detected on 68Ga-PSMA-11 scan in 3/58 patients (5.2%), and on 18F-Fluciclovine scan in 1/58 patients (1.7%). Extrapelvic lymph node metastases were detected in 24/58 patients (41.4%) on 18F-Fluciclovine PET/CT and in 30/58 patients (51.7%) on 68Ga-PSMA-11 PET/CT (p=0.26). In 6/58 patients (10.4%), distant lymph node metastases were only detected on 68Ga-PSMA-11. Bone metastases were detected in 15/58 patients (25.9%) on 18F-Fluciclovine PET/CT and in 21/58 patients (36.2%) on 68Ga-PSMA-11 PET/CT (p=0.23). In 8/58 patients (13.8%), bone metastases were only detected on 68Ga-PSMA-11 scan, and on 18F-Fluciclovine scan in 2/58 patients (3.5%). Conclusion: The strength of 18F-Fluciclovine in comparison to 68Ga-PSMA-11 lies in detecting local recurrence of prostate cancer especially when located in close anatomic relation to the urinary bladder. In the detection of distant metastases 18F-Fluciclovine is almost comparable to 68Ga-PSMA-11 PET/CT, with heterogeneity of tracer-avid disease across both scans. References: none

Impact of late pelvic acquisition on 68Ga-PSMA-11 PET/CT positivity rate and inter-rater reliability analysis
D. Nicolotti, F. Ceci, E. Pilati, B. Dionisi, I. Cerio, M. Finessi, V. Liberini, R. Passera, G. Bisi, D. Deandreis;
Nuclear Medicine Unit, Department of Medical Sciences, University of Turin, AOU Città della Salute e della Scienza di Torino, Turin, ITALY.

Aim/Introduction: The primary aim of this study was to evaluate the impact of late-pelvic scan on 68Ga-PSMA-11-PET/CT accuracy in localizing recurrent prostate cancer (PCa). Secondary objective was the comparison of inter-rater reliability between standard images and late acquisition, both in a per-patient and per-region analysis. Materials and Methods: 68Ga-PSMA-11-PET/CT is performed in our institution through a prospective, single-centre, study (protocol P-5315) in hormone-naïve recurrent PCa. Data of the first 65 consecutive patients who performed late-pelvic acquisition were retrospectively analysed. Administered activity was 2.5 (±0.5) MBq/Kg. Vertex to mid-thigh images were acquired at 60 (±10) minutes post-injection, 2.5 minutes per bed-position. Late-pelvic images were acquired at 120 (±15) minutes post-injection, 6 minutes per bed-position, 2 beds centered on pelvis. All images were acquired by the same scanner (Philips Gemini Dual-Slice EXP PET/CT) and interpreted by three independent experienced readers (R1=EP, R2=DN, R3=FC) using the same workstation (GE Advantage). Both acquisitions were interpreted in a per-patient and per-region (prostate bed; pelvic lymph-nodes; pre-sacral lymph-nodes; pelvic bones) analysis, using a 3-point scale (not suspected for PCa[0], undetermined[1] and suspected for PCa[2]). The impact of late-pelvic acquisition was evaluated as reader's confidence (decreasing of undetermined findings rate) and number of lesions detected. The degrees of agreement were assessed using intraclass correlation coefficients (ICC) and their CI95%, using a 2-way mixed, single measure, consistency model. ICC was interpreted as follow: 0.0, poor; 0.0-0.20, slight; 0.21-0.40, fair; 0.41-0.60, moderate; 0.61-0.80, substantial; 0.81-1.00, almost-perfect reproducibility. Results: Overall 68Ga-PSMA-11-PET/CT positivity rate increased from standard to late-pelvic acquisition: R1=43.07% to 60%, R2=49.23% to 64.62%, R3=40% to 55.38%, respectively. The reduction ratio of undetermined scans was: R1=18.46% (21.54% to 3.08%), R2=15.39% (21.54% to 6.15%), R3=15.38% (18.46% to 3.08%). All readers detected additional findings in late-scan compared to standard: R1=66 to 68; R2=64 to 72; R3=61 to 68. In the per-patient analysis the inter-observer agreement resulted substantial in standard scan (ICC=0.802, CI95%=0.733-0.834) and improved to almost-perfect in late-pelvic acquisition (ICC=0.851, CI95%=0.785-0.900). In the per-region analysis the inter-observer agreement improved especially in the prostate bed (ICC-standard=0.531, CI95%=0.390-0.661; ICC-late=0.606, CI95%=0.476-0.721), which remains however the more difficult district to evaluate, with moderate agreement. Despite high incidence of undetermined findings, pelvic lymph-nodes reached almost-perfect agreement both in standard (ICC=0.839, CI95%=0.770-0.892) and late-pelvic acquisition (ICC=0.878, CI95%=0.824-0.920). Conclusion: Our results show that the late-pelvic scan increases the overall 68Ga-PSMA-11-PET/CT positivity rate and the number of detected lesions, improves reader’s confidence and allows better inter-observer reproducibility. References: none.

Interobserver and intraobserver agreement of PSMA PET/CT according to miTNM and PSMA-RADS criteria
E. Demirci1, R. Akyel2, B. Caner1, N. Alan-Selçuk1, S. Güven Mese3, L. Kabasakal4;
1Yeditepe University, Department of Nuclear Medicine, Istanbul, TURKEY, 2Sisli Etfal Training and Research Hospital, Istanbul, TURKEY, 3Yeditepe University, Department of Medical Oncology, Istanbul, TURKEY, 4Istanbul University-Cerrahpasa, Department of Nuclear Medicine, Istanbul, TURKEY.

Aim/Introduction: Limited data is available about the interobserver variability of PSMA PET/CT and intraobserver variability has not been published. We aimed to investigate intra- and interobserver agreement for 68Ga-PSMA PET/CT interpretations according to miTNM and PSMA-RADS reporting templates and identify PET/CT findings with high variability and investigate diagnostic confidence levels of readers at specific PSMA PET/CT findings. We also investigated clinical outcome of interobserver variability. Materials and Methods: Patients (n=136) were selected with simple randomization. Anonymized images were evaluated by four experienced readers independently according to miTNM and PSMA-RADS templates. Diagnostic confidence levels of all findings also reported. Results evaluated with Feiss kappa test or intraclass correlation coefficients test(ICC) using 2-way mixed model for absolute agreement. Results: Readers agreed substantially for N and almost-perfectly for M categories (k=0.71 95%CI:0.67-0.79 and 0.78 95%CI:0.74-0.82). Moderate agreement was observed for initial T staging (k=0.63 95%CI:0.59-0.66). According to six-quadrant prostate reporting template, moderate or substantial agreement were observed for intraprostatic lesion localization (k=0.48 - 0.62). However, almost perfect interobserver agreement was observed for number of intraprostatic sites (ICC: 0.90 - %95CI:0.86-0.93). In Gleason Group 1 (GS 3+3) moderate reproducibility was observed (κ=0.531 %95CI:0.34 - 0.722). In Gleason Group ≥2 substantial reproducibility was observed (κ= 0.655 %95CI 0.55-0.761). Substantial agreement was observed for vesicula seminalis invasion (k=0.622 - 95%CI:0.533-0.71). All readers reported lower diagnostic confidence levels for «T3a» compared to other T stages (p<0.01). Three readers reported lower diagnostic levels for «T0» compared to other T stages (p<0.001). Two readers reported lower diagnostic confidence levels in patients with N1 compared to N0&2. In 12% (n=16) of the patients, only one reviewer reported clinically significant discordance (amendable errors with peer-review). In 9% (n=12) of the patient, the disagreement influences clinical management 3.8%(n=5). Almost-perfect intraobserver agreement was observed for 5-scale PSMA-RADS criteria (ICC=0.90 95%CI: 0.865-0.934). If lesions are grouped as benign (Score 1-2), suspicious (3) and malignant (4-5) moderate agreement was observed (k=0.5- 95%CI:0.434-0.564). Conclusion: PSMA PET has a substantial interobserver agreement and an almost perfect intra-observer agreement levels. Interobserver variance has a limited effect on clinical decisions. PSMA PET/CT has the highest interobserver agreement levels among the modalities used for imaging of prostate cancer. Lower (still moderate) interobserver agreement calculated for intraprostatic lesion localization due to limitation of 6-quadrant template. Peer-review significantly increases reproducibility and reliability of PSMA PET/CT. miTNM template is better for standardization of PSMA-PET reporting, compared to PSMA-RADS template. References: none

Evaluation of [68Ga]Ga-PSMA-PET/CT in therapy response assessment of PSMA-targeted radionuclide therapy in patients with castration resistant prostate cancer
J. Kurth1, J. Kretzschmar1, M. Heuschkel1, G. Kundt2, O. W. Hakenberg3, B. J. Krause1, S. M. Schwarzenboeck1;
1Department of Nuclear Medicine, Rostock University Medical Center, Rostock, GERMANY, 2Institute for Biostatistics and Informatics in Medicine and Ageing Research, Rostock University Medical Center, Rostock, GERMANY, 3Department of Urology, Rostock University Medical Center, Rostock, GERMANY.

Aim/Introduction: Aim of this study was to retrospectively evaluate the value of [68Ga]Ga-PSMA-PET/CT in monitoring early and late response to PSMA-targeted radionuclide therapy (Lu-177/Y-90) in castration resistant prostate cancer patients. Materials and Methods: 38 patients were referred for [68Ga]Ga-PSMA-PET/CT before the first cycle (PET 1), after one/two cycles (PET 2) and after a mean of 3 cycles (range 3 to 5 cycles) (PET 3) of PSMA radioligand therapy (Lu-177/Y-90) for patient-based therapy response assessment. PET-based therapy response was assessed according to EORTC and PERCIST criteria, for PET 2 vs. 1 (early response assessment, ERA) as well as for PET 3 vs. 1 (late response assessment, LRA). PET-classified response was compared to the results of ERA and LRA based on clinical criteria (best clinical response) and percentual change in PSA. Additionally, relationship between change of SUVmax/SUVmean and PSA (early and late, respectively) was evaluated. Prognostic value of initial SUVmax and SUVmean was assessed. Results: About 76% of the patients were classified as SD or PR (SD: 65.2%; PR: 10.9%) by clinical criteria and 77% by change in PSA as response criterion (SD: 46.7%; PR: 31.1%). However, by PET-based response assessment approx. 95% were classified as SD or PR (PERCIST: SD 23.9%; PR: 71.7%; EORTC: SD 23.9%; PR: 69.6%). Cohens kappa analysis showed no statistically significant concordance between EORTC/PERCIST based and clinical criteria/PSA-based ERA and LRA; kappa < 0.2. No statistically significant correlation was found between change in SUV and PSA in ERA and LRA; r < 0.1, for both ERA and LRA. No statistically significant prognostic value of initial SUVmax and SUVmean could be shown. Conclusion: Pretherapeutic [68Ga]Ga-PSMA-PET/CT is an essential prerequisite to detect sufficient expression of the molecular target. However, a significant correlation between [68Ga]Ga-PSMA-PET/CT based and clinical criteria/PSA-based therapy response assessment during the early and late course of PSMA targeted therapy could not be shown. The role of [68Ga]Ga-PSMA-PET/CT in this setting has to be evaluated in further studies. References: none

Preliminary results on response assessment using PSMA molecular imaging in patients with metastatic prostate cancer undergoing abiraterone
C. Liu, S. Hu, X. Xu, S. Song, Y. Zhang;
Fudan university cancer center, Shanghai, CHINA.

Aim/Introduction: A well-recognized barrier to therapy response assessment in castration-resistant prostate cancer (CRPC) is the lack of reliable surrogate markers of response to treatment coupled with a potentially exaggerated reliance on changes in serum prostate-specific antigen (PSA) as an indicator of treatment efficacy. Functional imaging modalities have been advocated as important markers of disease response and progression to different tumor entities.The aim of this study was to investigate the role of 99mTc-HYNIC-PSMA SPECT/CT in the early treatment evaluation and outcome prediction in patients with CRPC treated with long-term abiraterone. Materials and Methods: 99mTc-HYNIC-PSMA SPECT/CT was performed in 68 CRPC patients before and after 3-6 months treatment with abiraterone. Treatment response was assessed according to RECIST 1.1 and PERCIST 1.0 criteria, respectively. A decrease in serum PSA level of ≥50% was defined as biochemical response (BR). Univariate and multivariate Cox regression models addressed potential predictors of progression-free survival (PFS) and overall survival (OS). Results: Declines in PSA level of ≥50% were seen in 21 of 68 (31%) patients. The concordance rate between SPECT and BR was 81% (Cohen κ = 0.60; 95% CI, 0.33-0.90;P ≤ 0.01), higher than for that between SPECT and CT with 55% (κ = 0.40; 95% CI, 0.23-0.68; P ≤ 0.01), as well as that between CT and BR with 40% (κ = 0.43; 95% CI,0.26-0.67, P ≤ 0.05). In univariate analysis, PSA decline and PSMA SPECT/CT response predicted PFS and OS. In multivariate analysis, only PSMA SPECT/CT (progression vs nonprogression) remained significant for PFS and OS (p = 0.013 and p = 0.022, respectively). Conclusion: Early PSMA SPECT/CT can predict clinical outcome in CRPC beyond PSA response and conventional CT approach. Our data support further studies on PSMA SPECT/CT for abiraterone monitoring and outcome prediction in patients with CRPC. References: NO

Monocentric Intraindividual Comparison of 68Ga-RM2 and 68Ga-PSMA PET/CT in mCRPC
M. Heuschkel, J. Kurth, O. W. Hakenberg, S. Nitsch, S. M. Schwarzenböck, B. J. Krause;
Rostock University Medical Center, Rostock, GERMANY.

Aim/Introduction: 68Ga-PSMA PET/CT is the standard imaging procedure in recurrent Prostate Cancer. Beyond PSMA, different agents addressing other targets in Prostate Cancer have been developed, such as the GRPr-antagonist RM2. As well as PSMA it can equally be labeled with 68Ga and 177Lu in a theranostic approach. First evaluations in early stage recurrent Prostate Cancer showed a high detection rate of 68Ga-RM2 PET/CT and overlap with PSMA in this population (Minamimoto et al. JNM 2016).
The aim of this retrospective study was an intraindividual comparison of 68Ga-RM2 and 68Ga-PSMA PET/CT for lesion detection in patients with advanced metastatic castration resistant Prostate Cancer (mCRPC).
Materials and Methods: At the University Medical Center of Rostock we scanned 38 mCRPC patients with 68Ga-PSMA as well as 68Ga-RM2 to identify PSMA or RM2 positivity as prerequisite for radionuclide treatment with either 177Lu-PSMA or 177Lu-RM2. Visual uptake and semiquantitative parameters (SUVmax and SUVpeak) were compared in 277 metastatic reference lesions (5 local, 96 lymph nodes, 146 bone, 18 liver, 5 lung, 7 others). Results: In the visual assessment 3/38 patients showed neither PSMA- nor RM2-positive lesions. The remaining 35 patients showed a PSMA uptake of any grade, of whom only 3 showed a higher, 17 a much lower and 13 no RM2 uptake. 2/38 patients showed complementary RM2-positive / PSMA-negative and RM2-negative / PSMA-positive lesions.
SUVmax and SUVpeak were significantly higher for PSMA than for RM2 subsuming all reference lesions (p < 0.001) as well as in separate analysis of local recurrence (p = 0.043), lymph node (p < 0.001), bone (p < 0.001) and liver metastases (p = 0.022).
Conclusion: Most of the included advanced mCRPC patients showed a higher number of PSMA- than RM2-positive lesions and a higher uptake in 68Ga-PSMA compared to 68Ga-RM2 PET/CT. Nearly no tumor lesion showed a high PSMA and RM2 uptake at the same time, so there seems to be a different biological behavior of tumor cells. The small amount of patients with missing or only faint PSMA but high RM2 uptake maybe could benefit from the use of 68Ga-RM2 in restaging or in a theranostic approach including 177Lu-RM2-therapy. References: Minamimoto R et al., Pilot Comparison of ⁶⁸Ga-RM2 PET and ⁶⁸Ga-PSMA-11 PET in Patients with Biochemically Recurrent Prostate Cancer. J Nucl Med. 2016 Apr;57(4):557-62.

Localizing biochemical recurrence of prostate cancer using 68Ga-PSMA-11 PET/CT and 11C-acetate PET/CT
N. Regula, V. Kostaras, S. Johansson, C. Pulido, E. Lindström, M. Lubberink, I. Velikyan, J. Sörensen;
Uppsala University Hospital, Uppsala, SWEDEN.

Aim/Introduction: 68Ga-PSMA-11 PET/CT is increasingly used for staging of prostate cancer (PCa), but no comparative studies with 11C-acetate are available. This study aims to compare the performance of 68Ga-PSMA-11 PET/CT and 11C-acetate to locate the PCa recurrence in patients with biochemical relapse. Materials and Methods: Twenty-nine PCa patients, with PSA relapse after primary curative therapy, recruited from 2017-2018 were prospectively evaluated. PET/CT examination using 11C-acetate and 68Ga-PSMA-11 was performed on a Discovery MI scanner (GE Healthcare, Waukesha, WI). All available clinical data was recorded and evaluated. All highly suspicious lesions of local recurrence, regional or distal lymph node metastases and bone metastases were counted and evaluated regarding uptake intensity (SUVmean, SUVmax) and tumor volume (TV) for both tracers. Total TV and total lesion activity (TLAmean: summed SUVmean*TV; TLAmax: summed SUVmax*TV) were calculated. PSA at time of scan, the instrumental clinical finding at time of relapse, was correlated with findings of both scans. Results: Patients with median PSA of 5 ng/mL at time of PET scan (range 0.36-240 ng/mL) were included in this study. Median Gleason sum at time of diagnosis was 7. All pathological lesions showed higher uptake on 68Ga-PSMA-11 PET/CT (SUVmax 23.4±24.1) compared to 11C-acetate PET/CT (6.7±3.9; p=0.001). 68Ga-PSMA-11 PET/CT identified more lesions in 11 patients, less lesions in eight patients, identical in seven patients, same number of lesions but at different regions in one patient. Significantly more lymph node (n=107 vs n=80, McNemar test p=0.002) and bone lesions (n=54 vs n=35, McNemar test p=0.0001) were detected on 68Ga-PSMA-11 PET/CT. Nine patients (31%) with median PSA of 6.9 at time of scan showed upgraded disease status on 68Ga-PSMA-11 PET/CT, whereas 17 patients (59%) showed no change and 3 patients (10%) had downgraded disease status, compared to 11C-acetate PET/CT. Both scans were negative in two patients. PSA at time of scan correlated better with 68Ga-PSMA-11 PET/CT (spearman ρ >0.69, p<0.001) than 11C-acetate PET/CT (ρ>0.40, p<0.03). TLAmax had the highest correlation (ρ =0.80, p<0.0001) among the two modalities. Conclusion: 68Ga-PSMA-11 PET/CT identified significantly more suspicious lymph node and bone metastases compared to 11C-acetate PET/CT. PSA at time of scan was well correlated with the findings on 68Ga-PSMA-11 PET/CT. References: None

Impact of 18F-PSMA-1007 Ligand PET/CT in Multimodal Imaging of Recurrent Prostate Cancer
L. Dronka1,2, M. Radziņa1,2, M. Tirāne1,2, L. Zemniece1, M. Kalniņa3,2, L. Roznere3,2, V. Lietuvietis4, A. Freimanis4, E. Vjaters5;
1Institute of Radiology, Pauls Stradins Clinical University Hospital, Riga, LATVIA, 2Riga Stradins University Radiology Research Laboratory, Riga, LATVIA, 3Riga Stradins University Nuclear Medicine Clinic, Riga, LATVIA, 4Center of Urology, Riga East University Hospital, Riga, LATVIA, 5Center of Urology, Pauls Stradins Clinical University Hospital, Riga, LATVIA.

Aim/Introduction: Prostate cancer is generally a significant medical problem worldwide. Accurate localization of recurrent prostate cancer at low PSA values is a major challenge. Radiopharmaceutical 18F-PSMA-1007 has some advantageous characteristics in recurrent prostate cancer diagnostics. The aim of this study was to evaluate the diagnostic performance of the 18F-PSMA-1007 in patients with recurrent PCa, correlating with PSA levels, Gleason score(GS) and MRI Imaging results.
Materials and Methods: This comparative prospective study included 20 PCa patients with biochemical relapse (mean age 64.15 ± 6.2 years) referred for 18F-PSMA PET/CT. Whole-body PET/CT imaging was performed in all patients 120 min. after injection of 376 ± 71,92 MBq 18F-PSMA-1007. Prostatectomy and radiation therapy has been performed in 90% (N=18) and 40% (N=8) of the patients, respectively. PET/CT scans results were compared with GS, PSA level, doubling time and MRI Imaging results. Results: PET/CT confirmed pathological findings in 16/20 patients, 80%, respectively. MRI data was available for 13/20 patients and 76,9 % (N=10) showed local recurrence findings also in MRI while regional lymph nodes were detected by PET/CT vs. MRI, 11 vs. 5 cases, respectively (p=0.001). The higher SUVmax values were measured in pathological lymph nodes (range 2.7-21.3), main reduced detection on MRI was seen when SUVmax did not exceed value 10. The overall mean PSA level in study group was 1.62 ng/ml (range 0.38-21.6 ng/ml). The mean PSA doubling time - 2,63 months with high correlation to Gleason score (rs=0.747; p=0.001). The mean PSA level in PET positive finding group was 4,39 ng/ml, in PET negative finding group - 0,74 ng/ml. The median GS was 7 (range 5-9), and 75% (N=12) had a score above 7 (with prevalence of 3+4), the rate of pathological scans in these patients was 94% (N=11). In all cases, when GS exceed value 7, local and nodal PET/CT finding was positive. Overall method sensitivity was for PET/CT and MRI for local recurrence 83% vs 100% and for regional lymph nodes Se 100% vs. 62% with 37 % of false negative MRI nodes and 13% of false negative local recurrence results PET/CT (p=0.001).
Conclusion: 18F-PSMA-1007 PET/CT is superior to MRI in detection of recurrent PCa in regional metastatic lymph nodes, with substantial false negative results for local recurrence where MRI should be applied as confirmative method. Results are highly dependent on PSA level increase and Gleason score, confirming result stability in the groups with GS>7 and PSA doubling time>2.6 months.
References: None

Detection of biochemical recurrance of prostate cancer following radical prostatectomy through 18F-rhPSMA-7 positron emission tomography
L. Ulbrich1, M. Groenke2, A. Wurzer3, L. Jooss2, T. Maurer4, S. Kropf5, T. Horn6, H. Wester3, W. Weber2, M. Eiber2;
1MRI/TUM, Munich, GERMANY, 2Department of nuclear medicine, Klinikum rechts der Isar, TUM, Munich, GERMANY, 3Chair of Pharmaceutical Radiopharmacy, TUM, Munich, GERMANY, 4Martini-Klinik, UKE, Hamburg, GERMANY, 5Scintomics GmbH, Fuerstenfeldbruck, GERMANY, 6Department of Urology, Klinikum rechts der Isar, TUM, Munich, GERMANY.

Aim/Introduction: The new theranostic PSMA-targeting agent 18F-rhPSMA-7 allows fast radiolabeling with 18F and radiometals and shows only minimal renal excretion. Aim of this retrospective study was to evaluate the effficancy of 18F-rhPSMA-7PET in patients with biochemical recurrance (BCR) of prostate cancer after radical prostatectomy.
Materials and Methods: The 18F-rhPSMA-7PET/CT or PET/MRI datasets of patients with non-castrate BCR after radical prastatectomy imaged between June 2017 and June 2018 were retrospectively reviewed. One experienced nuclear medicine physician recorded all lesions suspicious for recurrent prostate cancer. Correlations between the detection rates and the patients' PSA level, their primary Gleason score and previous therapy (androgen deprivation therapy [ADT] and external beam radiation therapy [EBRT]) were evaluated. Results: 532 patients were included. Their median PSA level was 0.97 ng/mL (range, 0.01-372 ng/mL). The median uptake time between injection and start of the PET-scan was 76 min (range, 50-220 min). The median injected activity of 18F-rhPSMA-7 was 332 MBq (range: 142-486 MBq).423 (79.5%) patients with pathological findings were identified by 18F-rhPSMA-7 PET. 38.5% (15/39) patients with a PSA < 0.2 ng/mL presented with suspicious lesions. The detection rates were 63.8% (81/127), 86.5% (90/104), 85.3% (87/102) and 93.8% (150/160) at PSA levels of 0.2-< 0.5, 0.5-< 1, 1-< 2 and ≥ 2 ng/mL, respectively. Local recurrence was present in 42.1% (224) patients. Loco-regional, retroperitoneal and supraphragmatic lymph node metastases were observed in 41.4% (220), in 16.6% (88) and in 6.8% (36) of the patients, respectively. Findings indicating bone and visceral metastases were presented in 21.1% (112) and 4.0% (21) of patients.Higher detection rates were present in patients with an initial Gleason score ≥ 8 compared with scores ≤ 7 (85.0 vs. 77.2%, p<0.0001). Previous EBRT or ADT within 6 months prior imaging did not influence the detection rate (82.2% vs. 77.5%, p=0.185; 84.6% vs. 78.0%, p=0.114), respectively.
Conclusion: 18F-rhPSMA-7 PET offer high detection rates in patients with BCR after radical prostatectomy appear. These data indicate superiority to previous published data for 68Ga-PSMA-11.
References: none

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