PET/CT with prostate-specific membrane antigen (PSMA)-targeted tracers has been used in the diagnosis and staging of patients with clear cell renal cell carcinoma (ccRCC). For ccRCC primary tumors, PET parameters were shown to predict histologic grade and features. The aim of this study was to correlate PSMA PET/CT with histopathological findings in patients with metastatic recurrence of ccRCC. Patients with ccRCC who underwent PSMA-targeted PET/CT and subsequent histopathological evaluation of suspicious lesions were included. Specimens underwent immunohistochemical marking. Lesion diameter, volume and tracer uptake were correlated with the extent and intensity of molecular PSMA expression and with clinical findings. Twelve PET-positive lesions of nine patients were evaluated. Eleven ccRCC metastases and one prostate carcinoma were detected histopathologically. Molecular PSMA expression was detected in all lesions, which intensity and distribution did not correlate with PET parameters. PSMA-targeted PET/CT is a feasible tool for the evaluation of patients with ccRCC but cannot reliably predict histologic features of metastases. PSMA may also be expressed in malignant lesions other than ccRCC, leading to incidental detection of these tumors.

The biochemical relapse of prostate cancer is diagnostically challenging but of high clinical impact for subsequent patient treatment. PET/CT with radiolabeled PSMA ligands outperforms conventional diagnostic methods in the detection of tumor recurrence. Several radiopharmaceuticals were and are available for use. The aim of this study was to investigate whether the routinely applied [⁶⁸Ga]Ga-PSMA ligands PSMA-617, -I&T and -11 (HBED-CC) differ in physiological and pathological distribution, or in tumor detection rate. A retrospective evaluation of 190 patients (39 patients received PSMA-617, 68 patients PSMA-I&T and 83 patients PSMA-11) showed significant differences in tracer accumulation within all organs examined. The low retention within the compartments blood pool, bone and muscle tissue is a theoretical advantage of PSMA-11. Evaluation of tumor lesion uptake and detection rate did not reveal superiority of one of the three radiopharmaceuticals, neither in the whole population, nor in particularly challenging subgroups like patients with very low PSA levels. We conclude that all three [⁶⁸Ga]Ga-PSMA ligands are equally feasible in this clinically important scenario, and may replace each other in case of unavailability or production restrictions.

Holmium-166 microspheres are used for the transarterial radioembolization (TARE) treatment of primary and secondary liver cancers. In this study, its efficacy regarding local tumor control and integration into the oncological treatment sequence of the first 20 patients treated in our institution were examined. A total of twenty-nine ¹⁶⁶Ho-TARE procedures were performed to treat hepatocellular carcinoma (HCC, fourteen patients), metastatic colorectal cancer (mCRC, four patients), intrahepatic cholangiocarcinoma (ICC, one patient), and hemangioendothelioma of the liver (HE, one patient). In eight patients, ¹⁶⁶Ho-TARE was the initial oncologic treatment. In patients with HCC, the median treated-liver progression-free survival (PFS), overall PFS, and overall survival after ¹⁶⁶Ho-TARE were 10.3, 7.3, and 22.1 months; in patients with mCRC, these were 2.6, 2.9, and 20.6 months, respectively. Survival after ¹⁶⁶Ho-TARE in the patients with ICC and HE were 5.2 and 0.8 months, respectively. Two patients with HCC were bridged to liver transplantation, and one patient with mCRC was downstaged to curative surgery. In patients with HCC, a median treatment-free interval of 7.3 months was achieved. In line with previous publications, ¹⁶⁶Ho-TARE was a feasible treatment option in patients with liver tumors, with favorable clinical outcomes in the majority of cases. It was able to achieve treatment-free intervals, served as bridging-to-transplant, and did not prevent subsequent therapies.

Conventional ultrasound (US) is time-consuming, and results are subjected to high interobserver variability. In this study, the reliability of a novel thyroid US cine loop standard operating procedure (SOP) applied by non-physicians (Medical Technical Assistant, MTA) is investigated. Thirty-three consecutive patients (22 females, 11 males) were enrolled. Patients underwent conventional thyroid US performed by a nuclear medicine physician and additional MTA US cine loop according to a local SOP that includes transversal and sagittal cine loops covering the entire thyroid. The video sequences were transferred to the Picture Archiving and Communication System (PACS) for second reading purposes. MTA US data were not considered for medical reports but for blinded second reading review of the PACS images. The results of conventional physician US reports and reviewed MTA US cine loops were compared regarding size determinations of the thyroid and its nodules, as well as Thyroid Imaging Reporting and Data Systems (TIRADS) classification of all identified lesions. The results revealed very high concordance between conventional physician US and MTA US cine loop review for both size measurements and TIRADS classifications (r_(s) = 0.84–0.99, p < 0.0001 each). Minor technical impairments were identified. The evaluated thyroid US cine loop SOP enables reliable second reading results and can be applied by non-physicians.

To evaluate the microsphere outflow dynamics and residual Ho-166 activity during and after transarterial radioembolization planning and treatment procedures, and to assess the distribution and predilection sites of residual activity in the proprietary delivery set and the microcatheter. Fifteen planning and 12 therapeutic radioembolization procedures were performed with poly-l-lactic acid microspheres loaded with Ho-166. The amount and distribution of residual activity was assessed by dose calibrator measurements and SPECT imaging. The activity flow profile from the microcatheter was assessed dynamically. For planning procedures, different injection methods were evaluated in order to attempt to decrease the residual activity. The median residual activities for planning and treatment procedures using standard injection methods were 31.2% (range 17.3%–44.1%) and 4.3% (range 3.5%–6.9%), respectively. Planning residual activities could be decreased significantly with 2 injection methods similar to treatment procedures, to 17.5% and 10.9%, respectively (P = 0.002). Main predilection sites of residual microspheres were the 3-way stopcock and the outflow needle connector. During treatment procedures, more than 80% of the injected activity is transferred during the first 3 injection cycles. After treatment procedures with holmium-loaded microspheres, mean residual activity in the delivery set is reproducibly low and between reported values for glass and resin microspheres. The majority of microspheres is transferred to the patient during the second and third injection cycle. An estimated residual waste of 3% to 4% may be included in the treatment activity calculation. For planning procedures, a modified injection technique should be used to avoid high residual activities.

Transarterial radioembolization (TARE) with ¹⁶⁶Ho-loaded microspheres is an established locoregional treatment for hepatocellular carcinoma (HCC), introduced in 2010. This study evaluates the clinical outcome of patients with HCC who underwent ¹⁶⁶Ho-TARE with personalized dosimetry. Twenty-seven patients with 36 TARE procedures were analyzed. Treatment planning, execution, and evaluation was possible without complications in all cases. At the 3-month follow-up, disease control in the treated liver was achieved in 81.8% of patients (complete remission, partial remission, and stable disease in 36.4%, 31.8%, and 13.6%, respectively). The median overall survival (OS) was 17.2 months, and progression-free survival (PFS) in the treated liver was 11 months. Statistically significant positive correlations were observed between the achieved radiation dose for the tumor and both PFS (r = 0.62, p < 0.05) and OS (r = 0.48, p < 0.05), suggesting a direct dose–response relationship. The calculated achieved dose was 8.25 Gy lower than the planned dose, with relevant variance between planned and achieved doses in individual cases. These results confirm the efficacy of the ¹⁶⁶Ho-TARE holmium platform and underscore the potential of voxel-based, personalized dosimetry to improve clinical outcomes.