The efficacy of radioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) is currently being investigated for its application in patients with early-stage prostate cancer (PCa). However, little is known about PSMA expression in healthy organs in this cohort. Collectively, 202 [⁶⁸Ga]Ga-PSMA-11 positron emission tomography (PET) scans from 152 patients were studied. Of these, 102 PET scans were from patients with primary PCa and hormone-sensitive biochemically recurrent PCa and 50 PET scans were from patients with metastatic castration-resistant PCa (mCRPC) before and after three cycles of [¹⁷⁷Lu]Lu-PSMA-RLT. PSMA-standardized uptake values (SUV) were measured in multiple organs and PSMA-total tumor volume (PSMA-TTV) was determined in all cohorts. The measured PET parameters of the different cohorts were normalized to the bloodpool and compared using t- or Mann–Whitney U tests. Patients with early-stage PCa had lower PSMA-TTVs (10.39 mL vs. 462.42 mL, p < 0.001) and showed different SUVs in the thyroid, submandibular glands, heart, liver, kidneys, intestine, testes and bone marrow compared to patients with advanced CRPC, with all tests showing p < 0.05. Despite the differences in the PSMA-TTV of patients with mCRPC before and after [¹⁷⁷Lu]Lu-PSMA-RLT (462.42 mL vs. 276.29 mL, p = 0.023), no significant organ differences in PET parameters were detected. These suggest different degrees of PSMA-ligand binding among patients with different stages of PCa that could influence radiotoxicity during earlier stages of disease in different organs when PSMA-RLT is administered.

Background: The most important part of the follow-up of differentiated thyroid carcinoma (DTC) is the measurement of serum thyroglobulin (Tg). An increase of Tg levels indicates likely tumor recurrence. According to the guidelines of the European Society of Medical Oncology (ESMO) the follow-up should consist of serum Tg assays and a neck ultrasound, while the American Thyroid Association (ATA) recommends serum Tg assays, neck ultrasounds, and a diagnostic radioiodine Whole Body Scan (WBS) if non-stimulated Tg is greater than 10ng/mL or if Tg is rising. This study questions the necessity of a diagnostic WBS in patients with low stimulated Tg levels during the initial follow-up. Design: Retrospective data analysis. Methods: The data of 185 patients, who were in regular treatment and aftercare between 2015 and 2018 at the Department of Nuclear Medicine in Vienna, as well as the data of 185 patients, who were treated in Tbilisi between 2015 and 2019, were analysed. Results: There was a highly significant relationship between low stimulated Tg-levels (<0.5 ng/mL) and the outcome of the diagnostic WBS at the first follow-up (Χ² = 14.7, p < 0.001). A total of 31 of 370 patients (8.4%) had positive findings in the diagnostic WBS. 75 of 370 patients (19.74%) had stimulated Tg-levels >0.5 ng/ml. Conclusion: Our data suggest that the first follow-up, four to twelve months after the initial therapy of DTC, including the measurement of basal and stimulated Tg levels and Tg antibody levels, does not mandate a diagnostic WBS on all patients.

To investigate the use of kinetic parameters derived from direct Patlak reconstructions of [⁶⁸Ga]Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) to predict the histological grade of malignancy of the primary tumor of patients with prostate cancer (PCa). Thirteen patients (mean age 66 ± 10 years) with a primary, therapy-naïve PCa (median PSA 9.3 [range: 6.3–130 µg/L]) prior radical prostatectomy, were recruited in this exploratory prospective study. A dynamic whole-body [⁶⁸Ga]Ga-PSMA-11 PET/CT scan was performed for all patients. Measured quantification parameters included Patlak slope (Ki: absolute rate of tracer consumption) and Patlak intercept (Vb: degree of tracer perfusion in the tumor). Additionally, the mean and maximum standardized uptake values (SUVmean and SUVmax) of the tumor were determined from a static PET 60 min post tracer injection. In every patient, initial PSA (iPSA) values that were also the PSA level at the time of the examination and final histology results with Gleason score (GS) grading were correlated with the quantitative readouts. Collectively, 20 individual malignant prostate lesions were ascertained and histologically graded for GS with ISUP classification. Six lesions were classified as ISUP 5, two as ISUP 4, eight as ISUP 3, and four as ISUP 2. In both static and dynamic PET/CT imaging, the prostate lesions could be visually distinguished from the background. The average values of the SUVmean, slope, and intercept of the background were 2.4 (±0.4), 0.015 1/min (±0.006), and 52% (±12), respectively. These were significantly lower than the corresponding parameters extracted from the prostate lesions (all p < 0.01). No significant differences were found between these values and the various GS and ISUP (all p > 0.05). Spearman correlation coefficient analysis demonstrated a strong correlation between static and dynamic PET/CT parameters (all r ≥ 0.70, p < 0.01). Both GS and ISUP grading revealed only weak correlations with the mean and maximum SUV and tumor-to-background ratio derived from static images and dynamic Patlak slope. The iPSA demonstrated no significant correlation with GS and ISUP grading or with dynamic and static PET parameter values. In this cohort of mainly high-risk PCa, no significant correlation between [⁶⁸Ga]Ga-PSMA-11 perfusion and consumption and the aggressiveness of the primary tumor was observed. This suggests that the association between SUV values and GS may be more distinctive when distinguishing clinically relevant from clinically non-relevant PCa.

Background: This retrospective case–control study aimed to investigate the effects of thyroid-stimulating hormone (TSH) suppression on vascular wall inflammation, assessed by [ ¹⁸ F]-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT). Vascular [ ¹⁸ F]FDG-uptake is highly correlated with arterial inflammation, which represents a major risk factor for atherosclerotic plaques. Methods: Forty patients with differentiated thyroid cancer underwent [ ¹⁸ F]FDG-PET/CTs under TSH suppression therapy following surgical removal of the thyroid and subsequent radioiodine ablation. The [ ¹⁸ F]FDG-uptake was measured in the carotid arteries, aortic arch, and the ascending, descending, and abdominal aorta. All measurements in the PET scans were normalized to body weight and corrected for blood pool activity in the superior vena cava, creating target-to-background ratios (TBRs). Twenty-five patients with euthyroid hormone status were used as a control group. In addition, to evaluate long-term changes, the follow-up PET/CTs of 24 thyroid carcinoma patients under continued TSH suppression therapy were analyzed. Results: In patients with TSH suppression, significantly higher arterial [ ¹⁸ F]FDG-uptake ( p < 0.001) was observed in the ascending aorta, aortic arch, abdominal aorta, carotid artery, and for all arterial vessels combined (mean TBR _max ± standard deviation [SD]: 1.8 ± 0.4, 1.8 ± 0.3, 1.9 ± 0.4, 1.4 ± 0.3, 1.7 ± 0.2, respectively) compared with the euthyroid control group (TBR _max ± SD: 1.4 ± 0.2, 1.4 ± 0.2, 1.4 ± 0.2, 1.1 ± 0.2, 1.3 ± 0.1, respectively). In the subgroup of patients who received an additional follow-up scan after a mean duration of 1.9 ± 1.1 years of continued TSH suppression therapy, no significant changes in arterial [ ¹⁸ F]FDG-uptake were found in the five arterial sites when both scans were compared over time ( p > 0.05). Conclusions: Our study suggests that patients under TSH suppression may experience a significant increase in vascular [ ¹⁸ F]FDG-uptake, a marker of arterial inflammation, and, therefore, might be at higher risk for cardiovascular disease. Interestingly, the duration of TSH suppression was not significantly associated with vascular [ ¹⁸ F]FDG-uptake in our study, indicating that the observed increase in arterial inflammation may not be influenced by the duration of TSH suppression.

Background: While TSH suppression is essential in patients with differentiated thyroid cancer (DTC) to reduce the risk of recurrence, it has also been linked to side effects, particularly a reduction in bone mineral density that may contribute to osteoporosis. However, previous studies investigating this association have yielded inconsistent results. This study aimed to evaluate bone density using Hounsfield units from PET/CT scans in a longitudinal analysis including both sexes. Methods: Patients with DTC under continuous TSH suppression who underwent two PET/CT scans were included. Hounsfield units were measured for each lumbar vertebra (L1–L5) in the CT by placing an elliptical region of interest (ROI) in the center of the vertebra, avoiding hyperdense edges. Laboratory parameters were also collected. Results: A total of 50 patients were included in the study (25 male, 25 female), with a mean age of 57.2 (±15.3) years at the time of the first scan. The mean duration of TSH suppression before the first scan was 3.7 ± 3.9 years, and the mean interval between both scans was 4.4 ± 4.0 years. At the follow-up scan, bone density was significantly lower compared with baseline for all lumbar vertebrae (L1–L5 combined and individually) (all p < 0.05). Subgroup analysis revealed a significant decline in women at L1, L2, L4, and L5 and for overall lumbar bone density, while men showed nonsignificant trends. Conclusions: Our study suggests a sustained reduction in vertebral bone density during TSH suppression. The results support routine monitoring in both sexes, risk stratification by age and duration of suppression, and, when oncologically appropriate, consideration of lower suppression intensity or initiation of bone-protective therapy in high-risk patients.