Effects of short- and long-term TSH suppression on lumbar bone mineral density in both genders using PET/CT

Abstract Iatrogenic subclinical hyperthyroidism is induced intentionally in patients with differentiated thyroid cancer to reduce the risk of tumor recurrence. This retrospective study aimed to investigate the effect of thyroid-stimulating hormone (TSH) suppressive therapy on bone mineral density in men and women. Two cohorts of endocrine cancer patients were compared. In cohort A, 42 patients with long-lasting suppressed serum TSH were assessed. Cohort B consisted of 41 euthyroid patients. Bone density was measured in the L1-L4 lumbar vertebrae of all patients using PET/CT scans performed for cancer staging. In 17 patients of cohort A who received a second PET/CT scan, bone density was measured again to provide longitudinal analysis. A non-significant difference in age (p = .572) and equal distribution of sex (p = .916) was determined when comparing both cohorts. A significant difference (p = .011) with a moderate effect (η2 = .08; 20.4%) was observed regarding higher bone mineral density (BMD^HU) in cohort B with normal TSH levels (M 160.63 ± 54.7 HU) versus cohort A under TSH suppression therapy (M 127.9 ± 59.5 HU) for a mean duration of 4.45 ± 2.64 years. Furthermore, no significant change in BMD^HU (p = .786) was found in those patients who received a second PET/CT scan after a mean observation time of 2.3 ± 1.2 years. In conclusion, long-lasting TSH suppression therapy caused a statistically significant decrease in BMD^HU while short-lasting therapy didn't. Therefore, we can assume a higher likelihood of osteoporosis in those patients under prolonged TSH suppression

Direct Patlak Reconstruction of [⁶⁸Ga]Ga-PSMA PET for the Evaluation of Primary Prostate Cancer Prior Total Prostatectomy: Results of a Pilot Study

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 p > 0.05). Spearman correlation coefficient analysis demonstrated a strong correlation between static and dynamic PET/CT parameters (all r ≥ 0.70, p 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