Ivan Santi

Influence of Trigger PSA and PSA Kinetics on 11C-Choline PET/CT Detection Rate in Patients with Biochemical Relapse After Radical Prostatectomy

The purpose of this study was to investigate the effect of total prostate-specific antigen (PSA) at the time of 11C-choline PET/CT (trigger PSA), PSA velocity (PSAvel), and PSA doubling time (PSAdt) on 11C-choline PET/CT detection rate in patients treated with radical prostatectomy for prostate cancer, who showed biochemical failure during follow-up. Methods: A total of 190 patients treated with radical prostatectomy for prostate cancer who showed an increase in PSA (mean, 4.2; median, 2.1; range, 0.2–25.4 ng/mL) were retrospectively enrolled. All patients were studied with 11C-choline PET/CT. Patients were grouped according to trigger PSA (PSA ≤ 1 ng/mL, 1 < PSA ≤ 2 ng/mL, 2 < PSA ≤ 5 ng/mL, and PSA > 5 ng/mL). In 106 patients, data were available for calculation of PSAvel and PSAdt. Logistic regression analysis was used to determine whether there was a relationship between PSA levels and PSA kinetics and the rate of detection of relapse using PET. Results: 11C-choline PET/CT detected disease relapse in 74 of 190 patients (38.9%). The detection rate of 11C-choline PET/CT was 19%, 25%, 41%, and 67% in the 4 subgroups—PSA ≤ 1 ng/mL (51 patients), 1 < PSA ≤ 2 ng/mL (39 patients), 2 < PSA ≤ 5 ng/mL (51 patients), and PSA > 5 ng/mL (49 patients)—respectively. Trigger PSA values were statistically different between PET-positive patients (median PSA, 4.0 ng/mL) and PET-negative patients (median PSA, 1.4 ng/mL) (P = 0.0001). Receiver-operating-characteristic analysis showed an optimal cutoff point for trigger PSA of 2.43 ng/mL (area under the curve, 0.76). In 106 patients, PSAdt and PSAvel values were statistically different between patients with PET-positive and -negative scan findings (P = 0.04 and P = 0.03). The 11C-choline PET/CT detection rate was 12%, 34%, 42%, and 70%, respectively, in patients with PSAvel < 1 ng/mL/y (33 patients), 1 < PSAvel ≤ 2 ng/mL/y (26 patients), 2 < PSAvel ≤ 5 ng/mL/y (19 patients), and PSAvel > 5 ng/mL/y (28 patients). The 11C-choline PET/CT detection rate was 20%, 40%, 48%, and 60%, respectively, in patients with PSAdt > 6 mo (45 patients), 4 < PSAdt ≤ 6 mo (20 patients), 2 < PSAdt ≤ 4 mo (31 patients), and PSAdt ≤ 2 mo (10 patients). There was no statistical difference between PET-positive and -negative scan detection rates according to the Gleason score, pT and N status, patient age, or duration between surgery and biochemical relapse. Trigger PSA and PSAvel were found to be independent predictive factors for a PET-positive result (P = 0.002; P = 0.04) and PSAdt was found to be an independent factor only in patients with trigger PSA less than 2 ng/mL (P = 0.05) using multivariate analysis. Conclusion: The 11C-choline PET/CT detection rate is influenced by trigger PSA, PSAdt, and PSAvel. This finding could be used to improve the selection of patients for scanning by reducing the number of false-negative scans and increasing the detection rate of disease in patients with early relapse and potentially curative disease.

Value of a Dixon-based MR/PET attenuation correction sequence for the localization and evaluation of PET-positive lesions

PurposeIn this study, the potential contribution of Dixon-based MR imaging with a rapid low-resolution breath-hold sequence, which is a technique used for MR-based attenuation correction (AC) for MR/positron emission tomography (PET), was evaluated for anatomical correlation of PET-positive lesions on a 3T clinical scanner compared to low-dose CT. This technique is also used in a recently installed fully integrated whole-body MR/PET system.MethodsThirty-five patients routinely scheduled for oncological staging underwent 18F-fluorodeoxyglucose (FDG) PET/CT and a 2-point Dixon 3-D volumetric interpolated breath-hold examination (VIBE) T1-weighted MR sequence on the same day. Two PET data sets reconstructed using attenuation maps from low-dose CT (PETAC_CT) or simulated MR-based segmentation (PETAC_MR) were evaluated for focal PET-positive lesions. The certainty for the correlation with anatomical structures was judged in the low-dose CT and Dixon-based MRI on a 4-point scale (0–3). In addition, the standardized uptake values (SUVs) for PETAC_CT and PETAC_MR were compared.ResultsStatistically, no significant difference could be found concerning anatomical localization for all 81 PET-positive lesions in low-dose CT compared to Dixon-based MR (mean 2.51 ± 0.85 and 2.37 ± 0.87, respectively; p = 0.1909). CT tended to be superior for small lymph nodes, bone metastases and pulmonary nodules, while Dixon-based MR proved advantageous for soft tissue pathologies like head/neck tumours and liver metastases. For the PETAC_CT- and PETAC_MR-based SUVs (mean 6.36 ± 4.47 and 6.31 ± 4.52, respectively) a nearly complete concordance with a highly significant correlation was found (r = 0.9975, p < 0.0001).ConclusionDixon-based MR imaging for MR AC allows for anatomical allocation of PET-positive lesions similar to low-dose CT in conventional PET/CT. Thus, this approach appears to be useful for future MR/PET for body regions not fully covered by diagnostic MRI due to potential time constraints.

FDG–PET in the assessment of patients with follicular lymphoma treated by ibritumomab tiuxetan Y 90: multicentric study

BACKGROUND The aim of this study is the 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) evaluation following radioimmunotherapy (RIT) with ibritumomab tiuxetan Y 90 in patients with non-Hodgkins follicular lymphoma (FL). MATERIALS AND METHODS We retrospectively analyzed data from 59 relapsed or refractory FL patients treated with ibritumomab tiuxetan Y 90 in four different PET centers who had a PET scan carried out before and after RIT. Possible predictive factors of progression-free survival (PFS) were studied through univariate and multivariate analysis. RESULTS The post-RIT PET documented 45.8% complete responders (CR), 25.4% partial responders (PR) and 28.8% nonresponders [stable disease + progressive disease], with an overall survival of 71.2% (range 59.5%-90.9%). With a median follow-up period of 23 months, the univariate analysis documented a statistically significant relation between disease extent before RIT and response to treatment with respect to PFS (P = 0.015), while all the other prognostic factors showed no significant correlation. When carrying out the multivariate analysis, post-RIT PET resulted as the lonely independent predictor of PFS (P < 0.00001). CONCLUSIONS RIT is an effective therapy in FL patients, as confirmed in our study too. Disease extension before treatment and response to RIT, as assessed by FDG-PET, result as main predictors of PFS, with the post-RIT PET result being the only independent predictive factor.

Automated Synthesis of 68Ga-DOTA-TOC with a Cationic Purification System: Evaluation of Methodological and Technical Aspects in Routine Preparations

BACKGROUND AND OBJECTIVE Gallium-68 is a PET isotope available in each nuclear medicine departments, even those not equipped with a cyclotron, since it is easily obtained by eluting compact and transportable generator system. The preparation of Ga-68 DOTA-labeled compounds is performed by remotely controlled automated systems developed in order to ensure production efficiency, reproducibility of the results, fast reaction time, to facilitate the synthesis and minimize the radiation exposure. Many automatic synthesis systems are available on the radiopharmaceutical market, however, they requires some technical adaptations for routine use. We reported the [68Ga]Ga-DOTA-TOC production by automated cassette-based theranostic synthesizer system used in combination with a disposable GMP grade cassette system for cationic purification. METHODS The synthesizer is integrated with the 68Ge/68Ga generator systems and it allows to perform elution, eluate purification and radiolabeling in about 38 minutes. We have performed in 2 year (January 2016 - January 2018) over 100 [68Ga]Ga-DOTA-TOC preparations. RESULTS The average synthesis yield of radiopharmaceutical production was 54.4 ± 2.3 % and the radiochemical purity average was found 96.94 ± 0.74 %. Only three [68Ga]Ga-DOTA-TOC preparations have failed. CONCLUSION The methodology and the adopted technical solutions allowed to obtain a high quality radiopharmaceutical product as required by the European Pharmacopoeia.

Parathyroid Imaging with SPECT-CT

Hyperparathyroidism (HPT) is a common endocrine disorder affecting approximately 1 in 500 women and 1 in 2,000 men. The clinical or chemical diagnosis is commonly seen in the 5th through 7th decades of life [1]. Primary hyperparathyroidism (pHPT) is caused by a solitary parathyroid adenoma in approximately 85% of cases, whereas the remaining cases are often secondary HPT due to glandular hyperplasia, multiple adenomas and, very rarely, also parathyroid carcinomas [2].