[en] The aim of this prospective study was to compare the potential value of ¹⁸F fluorocholine (FCH) and ¹⁸F fluoride positron emission tomography (PET)-CT scanning for the detection of bony metastases from prostate cancer. Thirty-eight men (mean age, 69±8 years) with biopsy-proven prostate cancer underwent both imaging modalities within a maximum interval of 2 weeks. Seventeen patients were evaluated preoperatively, and 21 patients were referred for post-operative evaluation of suspected recurrence or progression based on clinical algorithms. The number, sites and morphological patterns of bone lesions on ¹⁸F FCH and ¹⁸F fluoride PET-CT were correlated: Concordant lesions between the two modalities with corresponding changes on CT were considered to be positive for malignancy; discordant lesions were verified by follow-up examinations. The mean follow-up interval was 9.1 months. Overall, 321 lesions were evaluated in this study. In a lesion-based analysis, a relatively close agreement was found between these two imaging modalities for detection of malignant bone lesions (kappa=0.57), as well as in a patient-based analysis (kappa=0.76). Sixteen malignant sclerotic lesions with a high density were negative in both ¹⁸F FCH and ¹⁸F fluoride PET-CT [ mean Hounsfield unit (HU), 1,148±364]. There was also a significant correlation between tracer intensity by SUV and density of sclerotic lesions by HU both in ¹⁸F FCH PET-CT (r=-0.28, p<0.006) and ¹⁸F fluoride PET-CT (r=-0.20, p<0.05). The sensitivity, specificity and accuracy of PET-CT in the detection of bone metastases in prostate cancer was 81%, 93% and 86% for ¹⁸F fluoride, and 74% (p=0.12), 99% (p=0.01) and 85% for FCH, respectively. ¹⁸F FCH PET-CT led to a change in the management in two out of 38 patients due to the early detection of bone marrow metastases. ¹⁸F fluoride PET-CT identified more lesions in some patients when compared with ¹⁸F FCH PET-CT but did not change patient management. FCH PET-CT may be superior for the early detection (i.e. bone marrow involvement) of metastatic bone disease. In patients with FCH-negative suspicious sclerotic lesions, a second bone-seeking agent (e.g. ¹⁸F fluoride) is recommended. ¹⁸F fluoride PET-CT demonstrated a higher sensitivity than ¹⁸F FCH PET-CT, but the difference was not statistically significant. Furthermore, ¹⁸F fluoride PET could be also negative in highly dense sclerotic lesions, which presumably reflects the effect of treatment. It will be important to clarify in future studies whether these lesions are clinically relevant when compared with metabolically active bone metastases. (orig.)

[en] In this prospective study, we evaluated the optimal time-point for ⁶⁸Ga-PSMA-11 PET/CT acquisition in the assessment of prostate cancer. We also examined, for the first time the feasibility of tracer production using a PSMA-11 sterile cold-kit in the clinical workflow of PET/CT centres. Fifty prostate cancer patients (25 staging, 25 biochemical recurrence) were enrolled in this study. All patients received an intravenous dose of 2.0 MBq/kg body weight ⁶⁸Ga-PSMA-11 prepared using a sterile cold kit (ANMI SA, Liege, Belgium), followed by an early (20 min after injection) semi-whole-body PET/CT scan and a standard-delay (100 min after injection) abdominopelvic PET/CT scan. The detection rates with ⁶⁸Ga-PSMA-11 were compared between the two acquisitions. The pattern of physiological background activity and tumour to background ratio were also analysed. The total preparation time was reduced to 5 min using the PSMA-11 sterile cold kit, which improved the final radionuclide activity by about 30% per single ⁶⁸Ge/⁶⁸Ga generator elution. Overall, 158 pathological lesions were analysed in 45 patients (90%) suggestive of malignancy on both (early and standard-delay) ⁶⁸Ga-PSMA PET/CT images. There was a significant (p < 0.001) increase in SUVmax on delayed images in suspicious prostates (11.6 ± 8.2 to 14.8 ± 1.0) and lymph nodes (LNs; 9.7 ± 5.9 to 12.3 ± 8.8), while bone lesions showed no significant increase (8.5 ± 5.6 to 9.2 ± 7.0, p = 0.188). However, the SUVmax of suspicious lesions on early images was adequate to support the criteria for correct interpretation (mean SUVmax 9.83 ± 6.7).In 26 of 157 lesions, but a decrease in SUV was seen, mostly in subcentimetre lesions in patients with multiple metastases. However, it did not affect the staging of the disease or patient management. The tumour to background ratio of primary prostate lesions and LNs showed a significant (p < 0.001) increase from the early to the standard-delay acquisition, but no significant increase was seen in bony lesions (p = 0.11). The PSMA-11 sterile cold kit seems to be feasible for use in routine clinical practice, and it has a shorter radionuclide preparation time and is less operator-dependent than the synthesizer-based production method. In addition, early ⁶⁸Ga-PSMA-11 PET/CT imaging seems to provide a detection rate comparable with that of standard-delay imaging. Furthermore, the shorter preparation time using the ⁶⁸Ga-PSMA-11 sterile cold kit and promising value of early PET/CT scanning could allow tailoring of imaging protocols which may reduce the costs and improve the time efficiency in PET/CT centres. (orig.)

[en] The bombesin derivative RM2 is a GRPr antagonist with strong binding affinity to prostate cancer (PCa). In this study, the impact of [${}^{68}$Ga]Ga-RM2 positron emission tomography-computed tomography (PET-CT) for the detection of primary PCa was compared with that of [${}^{18}$F]FCH PET-CT and multiparametric magnetic resonance imaging (mpMRI). This phase I/II study was conducted in 30 biopsy-positive PCa subjects. The patients were stratified into high (10 patients), intermediate (10 patients), and low risk (10 patients) for extraglandular metastases as defined by National Comprehensive Cancer Network (NCCN) criteria (NCCN Clinical Practice Guidelines in Oncology,). The prostate gland was classified in 12 anatomic segments for data analysis of the imaging modalities as well as histopathologic findings. The segment with the highest radiotracer uptake was defined as the "index lesion." All cases were scheduled to undergo prostatectomy with pelvic lymph node (LN) dissection in intermediate- and high-risk patients. Intraprostatic and pelvic nodal [${}^{68}$Ga]Ga-RM2 and [${}^{18}$F]FCH PET-CT findings were correlated with mpMRI and histopathologic results. Of the 312 analyzed regions, 120 regions (4 to 8 lesions per patient) showed abnormal findings in the prostate gland. In a region-based analysis, overall sensitivity and specificity of [${}^{68}$Ga]Ga-RM2 PET-CT in the detection of primary tumor were 74% and 90%, respectively, while it was 60% and 80% for [${}^{18}$F]FCH PET-CT and 72% and 89% for mpMRI. Although the overall sensitivity of [${}^{68}$Ga]Ga-RM2 PET-CT was higher compared to that of [${}^{18}$F]FCH PET-CT and mpMRI, the statistical analysis showed only significant difference between [${}^{68}$Ga]Ga-RM2 PET-CT and [${}^{18}$F]FCH PET-CT in the intermediate-risk group (p = 0.01) and [${}^{68}$Ga]Ga-RM2 PET-CT and mpMRT in the high-risk group (p = 0.03). In the lesion-based analysis, there was no significant difference between SUVmax of [${}^{68}$Ga]Ga-RM2 and [${}^{18}$F]FCH PET-CT in the intraprostatic malignant lesions ([${}^{68}$Ga]Ga-RM2: mean SUVmax: 5.98 ± 4.13, median: 4.75; [${}^{18}$F]FCH: mean SUVmax: 6.08 ± 2.74, median: 5.5; p = 0.13). [${}^{68}$Ga]Ga-RM2 showed promising PET tracer for the detection of intraprostatic PCa in a cohort of patients with different risk stratifications. However, significant differences were only found between [${}^{68}$Ga]Ga-RM2 PET-CT and [${}^{18}$F]FCH PET-CT in the intermediate-risk group and [${}^{68}$Ga]Ga-RM2 PET-CT and mpMRT in the high-risk group. In addition, GRP-R-based imaging seems to play a complementary role to choline-based imaging for full characterization of PCa extent and biopsy guidance in low- and intermediate-metastatic-risk PCa patients and has the potential to discriminate them from those at higher risks. [${}^{68}$Ga]Ga-RM2 is a promising PET tracer with a high detection rate for intraprostatic PCa especially in intermediate-risk prostate cancer patients. GRPr-based imaging seems to play a complementary role to choline-based or PSMA-based PET/CT imaging in selected low- and intermediate-risk PCa patients for better characterization and eventually biopsy guidance of prostate cancer disease.