68Ga Prostate-Specific Membrane Antigen Research Articles

Predictors of Metastasis in 68GA-Prostate Specific Membrane Antigen Pet-CT in the Primary Staging of Prostate Cancer.

Background: The objective of this study was to investigate factors influencing Gallium 68 Prostate Specific Membrane Antigen Positron Emission Tomography (Ga68 PSMA PET-CT) uptake for primary staging in prostate cancer. Methods: Retrospective analysis was conducted on 499 non-metastatic and 243 de novo metastatic prostate cancer cases undergoing Ga68 PSMA PET-CT. Demographic, clinical, and imaging data were collected and analyzed. Multivariate logistic regression determined independent risk factors for metastasis detection on Ga68 PSMA PET-CT. Results: Metastatic cases showed higher levels of total PSA, PSA density (dPSA) and biopsy ISUP grade group compared to non-metastatic cases. Multivariate analysis identified cT2 stage and dPSA as independent predictors of metastasis detection on Ga68 PSMA PET-CT. Conclusions: Ga68 PSMA PET-CT plays a crucial role in prostate cancer staging, with identified factors such as clinical T stage and dPSA significantly impacting its diagnostic accuracy. These findings underscore the importance of Ga68 PSMA PET-CT in refining clinical staging and guiding treatment decisions for prostate cancer patients.

Diagnostic Accuracy of a Combination of Preoperative 68-Ga Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography and Multiparametric Magnetic Resonance Imaging in Localized Prostate Cancer

Introduction: Prostate cancer (PCa) is a common and leading course of cancer-related death in men. Although there are studies on multiparametric magnetic resonance imaging (MpMRI) with good diagnostic results in detecting clinically significant PCa, new methods have been investigated due to the low positive predictive values. In this context, prostate-specific membrane antigen positron emission tomography (PSMA PET) emerges as an alternative imaging method to MpMRI. This study aimed to compare 68Ga PSMA I&T-PET/CT and MpMRI in determining tumor location. Methods: Preoperative MpMRI and 68Ga PSMA I&T-PET/CT scans and pathology specimens of patients who underwent radical prostatectomy for PCa at our clinic between 2018 and 2021 were retrospectively evaluated. PSMA I&T-PET/CT, MpMRI, combined imaging were compared for tumor localization according to histopathological data. Results: In terms of tumor localization, MpMRI demonstrated overall accuracy rates of 75.9% (p kappa [κ] 0.0001* [0.525]). 68Ga PSMA I&T-PET/CT showed 71.5% (p κ 0.0001* [0.438]). For the combined imaging approach, the overall accuracy rate was calculated as 79.2% (p κ 0.0001* [0.576]). Additionally, high diagnostic accuracy was achieved for the combined imaging approach, particularly in the intermediate ISUP group. Moreover, SUVmax was calculated as 6.37. Conclusion: The combined use of 68Ga PSMA I&T-PET/CT and MpMRI has high diagnostic rates. However, the high cost is a significant disadvantage that limits their routine combined use.

68Ga Prostate-specific Membrane Antigen Uptake in Metastatic Medullary Thyroid Carcinoma.

We present the case of a 58-year-old man with advanced medullary thyroid carcinoma who had a treatment history with different types of modalities. In the follow-up, the patient had rising calcitonin and CEA levels. Metastatic lymph nodes, liver, and bone metastases with varying degrees of uptake were detected on 18F-fluorodeoxyglucose (FDG) and 68Ga-DOTATATE positron emission tomography/computed tomography (PET/CT). 68Ga prostate-specific membrane antigen (PSMA) PET/CT was performed to explore whether the patient might have a chance for PSMA-targeted radionuclide therapy, and increased PSMA expression was noted in most of the metastatic lesions, even some of which have higher PSMA uptake than 18F-FDG and 68Ga-DOTATATE.

Oncological Outcomes in Men With Favorable Intermediate Risk Prostate Cancer Enrolled in Active Surveillance.

To evaluate the long-term oncological outcomes in men with intermediate risk prostate cancer (PCa) enrolled in active surveillance (AS). From April 2015 to December 2022, 30 men with Gleason score 3+4/ISUP Grade Group2 (GG2), greatest percentage of cancer (GPC) ≤50%, Gleason pattern 4 ≤10%, ≤3 positive biopsy cores were enrolled in AS. All patients underwent confirmatory transperineal saturation biopsy (SPBx: 20 cores) 12 months from diagnosis plus multiparametric magnetic resonance (mpMRI) evaluation. At the last follow-up, 68Ga prostate-specific membrane antigen (PSMA) positron-emission tomography (PET)/computed tomography (CT) was added: lesions with PIRADS score ≥3 and/or standardized uptake value (SUVmax) >5 were submitted to four targeted cores. Three out of 30 (10%) men with GG2 PCa were reclassified at confirmatory biopsy. At the last follow-up (median 5.2 years), only 2 of 27 (7.4%) men were reclassified and 23/30 (76.6%) continued AS. Men with favorable GG2 PCa enrolled in AS have good long-term oncological results. The use of selective criteria (i.e., SPBx, mpMRI, PSMA PET/CT) reduces the risk of reclassification.

68 Ga-PSMA Uptake in Solar Elastosis.

68 Ga-prostate specific membrane antigen (PSMA) PET/CT scan for staging revealed increased 68 Ga-PSMA uptake in solar elastosis in a patient with prostate cancer. Solar elastosis is a degenerative condition of elastic tissue in the dermis caused by prolonged sun exposure. A few studies have demonstrated 68 Ga-PSMA uptake in cutaneous lesions. This case illustrates another instance of a benign cutaneous lesion accompanied by increased 68 Ga-PSMA uptake.

Total-body PET/CT with half-dose [68Ga]Ga-PSMA-11 for biochemical recurrent prostate cancer: comparable diagnostic value to short axial field-of-view PET/CT with full-dose [68Ga]Ga-PSMA-11.

The objective of this study was to evaluate the diagnostic performance and image quality of total-body positron emission tomography/computed tomography (PET/CT) imaging using a half-dose of [68Ga]Ga-prostate specific membrane antigen ([68Ga]Ga-PSMA) radiotracer, compared to conventional short axial field-of-view PET/CT imaging using a full dose of [68Ga]Ga-PSMA. This retrospective study enrolled 52 patients with biochemical recurrent (BCR) prostate cancer after radical prostatectomy who underwent total-body PET/CT with a half-dose (0.9-1.1MBq/kg) of [68Ga]Ga-PSMA. These patients were matched by baseline characteristics to another 52 BCR patients after prostatectomy who underwent conventional PET/CT with a full dose (1.8-2.2MBq/kg) of [68Ga]Ga-PSMA. The half-dose group was further divided into 5-min (G5) and 2-min (G2) acquisition subgroups. Image quality was assessed through subjective analysis using a 5-point scale and objective measurements of standard uptake value maximum (SUVmax), standard uptake value mean (SUVmean), background variation (BV) of the liver, blood pool, and parotid glands. Additionally, SUVmax and tumor-to-background ratio (TBR) were calculated for lesions. No significant difference in subjective image quality was found between the G2 and full-dose groups (p > 0.05). PET/CT image quality was significantly higher for the G5 versus G2 (p < 0.001) and full-dose groups (p < 0.001). TBR did not differ between the G2 and full-dose groups (4.23 ± 5.21 vs 4.22 ± 3.97, p = 0.99). Liver BV was significantly lower for G2 versus full-dose groups (0.16 ± 0.03 vs 0.20 ± 0.05, p < 0.001). Total-body PET/CT with a half-dose [68Ga]Ga-PSMA yields image quality superior or comparable to that of conventional PET/CT. The utilization of total-body [68Ga]Ga-PSMA PET/CT meets the diagnostic demands of BCR patients, particularly those who exhibit reduced tolerance to prolonged horizontal positioning and scan durations, while simultaneously reducing radiation exposure for the subjects.

Isolated Castrate-resistant Prostate Cancer Metastasis to Both Adrenal Glands Detected on 68Ga PSMA PET/CT.

A 61-year-old male patient, who had undergone radical prostatectomy, underwent 68Ga labeled prostate-specific membrane antigen (PSMA) positron emission tomography/computerized tomography (PET/CT) for evaluation of suspected biochemical recurrence of prostate cancer (PCa). PET/CT scan showed increased 68Ga PSMA expressions in hypodense mass lesions in both adrenal gland localizations. An adrenal gland tru-cut biopsy was performed for the right side, which showed poor-differentiated carcinoma metastases associated with the patient's high-grade PCa. As far as we could determine based on an extensive literature search, this is the second case in which isolated adrenal metastasis was detected by 68Ga PSMA PET/CT study in a patient with PCa.

Differential privacy preserved federated transfer learning for multi-institutional 68Ga-PET image artefact detection and disentanglement

PurposeImage artefacts continue to pose challenges in clinical molecular imaging, resulting in misdiagnoses, additional radiation doses to patients and financial costs. Mismatch and halo artefacts occur frequently in gallium-68 (68Ga)-labelled compounds whole-body PET/CT imaging. Correcting for these artefacts is not straightforward and requires algorithmic developments, given that conventional techniques have failed to address them adequately. In the current study, we employed differential privacy-preserving federated transfer learning (FTL) to manage clinical data sharing and tackle privacy issues for building centre-specific models that detect and correct artefacts present in PET images.MethodsAltogether, 1413 patients with 68Ga prostate-specific membrane antigen (PSMA)/DOTA-TATE (TOC) PET/CT scans from 3 countries, including 8 different centres, were enrolled in this study. CT-based attenuation and scatter correction (CT-ASC) was used in all centres for quantitative PET reconstruction. Prior to model training, an experienced nuclear medicine physician reviewed all images to ensure the use of high-quality, artefact-free PET images (421 patients’ images). A deep neural network (modified U2Net) was trained on 80% of the artefact-free PET images to utilize centre-based (CeBa), centralized (CeZe) and the proposed differential privacy FTL frameworks. Quantitative analysis was performed in 20% of the clean data (with no artefacts) in each centre. A panel of two nuclear medicine physicians conducted qualitative assessment of image quality, diagnostic confidence and image artefacts in 128 patients with artefacts (256 images for CT-ASC and FTL-ASC).ResultsThe three approaches investigated in this study for 68Ga-PET imaging (CeBa, CeZe and FTL) resulted in a mean absolute error (MAE) of 0.42 ± 0.21 (CI 95%: 0.38 to 0.47), 0.32 ± 0.23 (CI 95%: 0.27 to 0.37) and 0.28 ± 0.15 (CI 95%: 0.25 to 0.31), respectively. Statistical analysis using the Wilcoxon test revealed significant differences between the three approaches, with FTL outperforming CeBa and CeZe (p-value < 0.05) in the clean test set. The qualitative assessment demonstrated that FTL-ASC significantly improved image quality and diagnostic confidence and decreased image artefacts, compared to CT-ASC in 68Ga-PET imaging. In addition, mismatch and halo artefacts were successfully detected and disentangled in the chest, abdomen and pelvic regions in 68Ga-PET imaging.ConclusionThe proposed approach benefits from using large datasets from multiple centres while preserving patient privacy. Qualitative assessment by nuclear medicine physicians showed that the proposed model correctly addressed two main challenging artefacts in 68Ga-PET imaging. This technique could be integrated in the clinic for 68Ga-PET imaging artefact detection and disentanglement using multicentric heterogeneous datasets.

Head-to-head comparisons of 68Ga-PSMA-11 and 18F-FDG PET/CT in evaluating patients with upper tract urothelial carcinoma: a prospective pilot study.

To prospectively compare the uptake of 68Ga-prostate specific membrane antigen (68Ga-PSMA)-11 and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in upper tract urothelial carcinoma (UTUC) and investigate the correlation between radiological parameters and pathological features of UTUC. Clinicopathologic and imaging data were collected from 10 UTUC patients who underwent preoperative 68Ga-PSMA-11 and 18F-FDG PET/CT scans. The diagnostic capabilities of both imaging techniques were analyzed and compared in UTUC. Angiogenesis in the malignancies was assessed using Chalkley counting and the expression of folate hydrolase 1 (FOLH1) and glucose transporter1 (GLUT1) in UTUC were evaluated in the surgical specimens. Double immunofluorescence staining of PSMA and CD34 was used to examine tumor neovascularization. Tracer uptake and expression were compared and explored. Additionally, 10 patients with clear cell renal cell carcinoma (ccRCC) were included for prospective, comparative research. Ten UTUC patients with 12 malignant lesions and another 10 ccRCC patients were included. 18F-FDG PET/CT demonstrated a more effective detection of UTUC foci compared to 68Ga-PSMA-11 PET/CT (the SUVmax of 18.48 ± 6.73 vs. 4.38 ± 1.45, P < 0.01). Immunohistochemical analysis revealed a statistically significant difference in the expression of PSMA and GLUT1 in UTUC (P = 0.048), with higher pathological grades showing more intense GLUT1 staining than PSMA (75% vs. 12.5%). The Chalkley counting of angiogenesis in ccRCC was significantly higher than that in UTUC (229.34 vs. 71.67), which was proportional to 68Ga-PSMA-11 PET/CT SUVmax (both P < 0.05). 18F-FDG PET/CT holds better clinical potential for evaluating UTUC and detecting lymph node metastasis compared to 68Ga-PSMA-11 PET/CT, likely due to the relatively scant expression of FOLH1 in tumor neovascular endothelium while the abundant expression of GLUT1 in malignancy. Furthermore, the lower neovascular density in UTUC should not be overlooked.

177Lu-PSMA radioligand therapy for patients with recurrent/metastatic (R/M) salivary gland cancer (SGC): A phase II pilot study.

6099 Background: New treatments are warranted due to limited systemic treatment options for SGC patients (pts). Gallium [68Ga]Ga prostate-specific membrane antigen (PSMA) PET imaging results in SGC pts have demonstrated PSMA expression of SGC and thus indicated that PSMA radionuclide therapy may be a useful option, especially in the case of adenoid cystic carcinoma (AdCC) and salivary duct carcinoma (SDC) subtypes. Therefore, this study (EudraCT number 2019-003857-27) evaluated the safety and efficacy of PSMA-targeted radionuclide therapy in AdCC and SDC pts. Methods: This was a single-center, single-arm, phase II pilot study. R/M AdCC (n = 10) and SDC (n = 5) pts with sufficient PSMA tracer uptake on [68Ga]Ga-PSMA PET imaging, i.e., ≥1 lesion ≥1.5cm with PSMA expression above mean liver level, were treated with 2-4 cycles of 7.4 GBq [177Lu]Lu-PSMA-I&amp;T, with an interval of 6±1 weeks. Baseline imaging was repeated for evaluation 4 weeks after cycle 2; in case of progressive disease (PD) per RECIST 1.1 the treatment was discontinued; otherwise, pts received the full treatment (4 cycles). All pts received whole body post-therapeutic imaging after 1, 24, 48, 72 h and 7d after each cycle. The primary endpoint was safety. Secondary endpoints include the objective response rate, progression-free survival (PFS), and overall survival (OS). Results: Between 6-2020 and 2-2023, 15 AdCC pts and 10 SDC pts were screened for eligibility. Five AdCC pts and 8 SDC pts were screen failures due to insufficient PSMA expression in 11 pts (AdCC n = 4; SDC n = 7) or due to brain metastases in 2 pts (AdCC n = 1; SDC n = 1). Ten AdCC and 2 SDC pts received at least one cycle of 7.4 GBq [177Lu]Lu-PSMA-I&amp;T. The most observed adverse events (grade 1-2) included: nausea (75%), dry mouth (75%), fatigue (67%), and anemia (58%). Two pts (17%) developed grade 3 toxicity; lymphocytopenia (n = 1) and hyponatremia (n = 1). No grade 4-5 toxicities were observed. Two pts (AdCC n = 1; SDC n = 1) received only 1 treatment cycle due to early PD. The interim-treatment evaluation resulted in the discontinuation of treatment after 2 cycles in an additional 3 AdCC and the second SDC pts due to PD. Six AdCC pts received the full treatment (4 cycles); no responses were observed; 3 pts (75%) showed stable disease of more than 3 months after treatment completion (5, 15 and 21 months); 3 pts showed PD at 3 months after treatment completion. Median PFS in 10 AdCC pts was 6.7 months (95%CI: 0.0-15.1); OS was not reached after a median follow-up of 11.9 months. Conclusions: [177Lu]Lu-PSMA-I&amp;T treatment in SGC pts is well-tolerated. The efficacy in AdCC was limited; only stable disease was achieved in 3 out of 10 pts. In most screened SDC pts, PSMA expression was insufficient to undergo [177Lu]Lu-PSMA-I&amp;T treatment; the 2 SDC pts included showed early PD. Dosimetry analyses will be performed to calculate the delivered radiation doses to organs at risk as well as tumor lesions. Clinical trial information: EUCTR2019-003857-27.

68Ga-PSMA PET/CT evaluation in men enrolled in prostate cancer Active Surveillance

To evaluate the accuracy of 68Ga-prostate specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) in the diagnosis of clinically significant prostate cancer (csPCa: Grade Group ≥ 2) in men enrolled in Active Surveillance (AS) protocol. From May 2013 to December 2021 200 men aged between 52 and 74 years (median age 63) with very low risk PCa were enrolled in an AS protocol study. During the follow up 48/200 (24%) men were upgraded and 10/200 (5%) decided to leave the AS protocol. After five years from confirmatory biopsy (range: 48-60 months) 40/142 (28.2%) consecutive patients were submitted to mpMRI and 68Ga-PSMA PET/CT imaging examinations before scheduled repeated biopsy. All the mpMRI (PI-RADS ≥ 3) and 68Ga-PET/TC standardized uptake value (SUVmax) ≥ 5 index lesions underwent targeted cores (mpMRI-TPBx and PSMA-TPBx) combined with transperineal saturation prostate biopsy (SPBx: median 20 cores). Multiparametric MRI and 68Ga-PSMA PET/CT showed 18/40 (45%) and 9/40 (22.5%) lesions suspicious for PCa. In 3/40 (7.5%) men a csPCa (GG2) was found; 68Ga-PSMA-TPBx vs. mpMRI-TPBx vs. SPBx diagnosed 2/3 (66.6%) vs. 2/3 (66.6%) vs. 3/3 (100%) csPCa, respectively. In detail, mpMRI and 68Ga-PSMA PET/TC demonstrated 16/40 (40%) vs. 7/40 (17.5%) false positive and 1 (33.3%) vs. 1 (33.3%) false negative results. Although 68PSMA PET/CT did not improve the detection for csPCa of SPBx (1 false negative result equal to 33.3% of the cases), at the same time, would have spared 31/40 (77.5%) scheduled biopsies showing a better diagnostic accuracy in comparison with mpMRI (83.3% vs. 70.2%).

Impact of 68Ga-PSMA PET/CT in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide.

48 Background: 68Ga prostate specific membrane antigen positron emission tomography/computed tomography (68Ga-PSMA PET/CT) is a highly sensitive diagnostic tool to detect prostate metastatic sites even at low levels of Prostate Specific Antigen (PSA). We evaluated the impact of 68Ga-PSMA PET/CT in patients treated with enzalutamide as first-line therapy for mCRPC. Methods: In an observational prospective study, 67 consecutive mCRPC patients were treated with enzalutamide 160 mg once daily in first-line for mCRPC. 68Ga-PSMA PET/CT was performed at baseline, after 3 months, during follow-up and at PSA/clinical progression. Patients were evaluated on a monthly basis for serological PSA response and safety. We measured at baseline the sum of metabolic total volume (SMTV), mean standardized uptake volume (SSUVmean), maximum standardized uptake volume (SSUVmax) and total lesion activity (STLA), which is the product of SMTV and SSUVmean, for a maximum of 20 lesions. These parameters together with baseline PSA level, Eastern Cooperative Oncology Group performance status (ECOG PS), Gleason Score (GS) and age were analyzed by univariate and multivariate Cox regression models as potential predictors of progression-free survival (PFS) and overall survival (OS). Results: At the moment of the present analysis, 58 mCRPC patients were considered fully evaluable. The median age was 75 years (range, 47-91), ECOG PS was 0 in 47 cases (81%), 1-2 in 11 (19%), GS was &lt;8 in 22 (38%), 8-10 in 36 (62%), the median baseline PSA was 2.66 µg/L (range 0.09-197). We observed a median SMTV of 5.73 cm3, median SSUVmax of 44.85, median SSUVmean of 25.80 and median STLA of 59.66. At the median follow-up of 52 months, median PFS was 28.9 months (95% CI 16.3-43.6), median OS was not reached (95% CI 36.8-not reached). In univariate analysis, SSUVmax and STLA were significant for PFS (p=0.015 and p=0.001, respectively) and OS (p=0.026 and p=0.019, respectively), while SSUVmean was significant only for OS (p=0.028). On multivariate analysis, STLA only remained significant for PFS (p&lt;0.001) and OS (p=0.026). Conclusions: The assessment of mCRPC by 68Ga-PSMA PET/CT before starting enzalutamide was associated with longer median PFS and OS compared to prior studies using standard imaging only. STLA, expression of both volume and intensity of 68Ga-PSMA uptake, appeared the strongest parameter able to predict PFS and OS.

Characteristics of Radiopharmaceutical Uptake in Primary Tumor and Metastatic Lesions of Prostate Carcinoma: Comparison of Oligometastatic with Multimetastatic Disease.

Oligometastases may generate secondary to indolent tumor biology. In this study, we investigated whether semiquantitative measures of 18F-fluorodeoxyglucose (FDG) and gallium-68 (68Ga) prostate-specific membrane antigen (PSMA) uptake of metastatic lesions and prostatic sites are different between oligometastatic (OM) and multimetastatic (MM) disease of prostate carcinoma (PC). Patients with PC, who underwent positron emission tomography/computed tomography (PET/CT) from October 2012 to February 2020 were retrospectively reviewed. Patients, whose reports were consistent with metastatic diseases were selected. Patients classified as with MM or OM disease. Maximum standardized uptake values (SUVmax) were calculated from metastatic lesions and the prostatic site. The median of the SUVmax results between patients with OM and MM disease were compared. A totally 145 patients with a mean age of 71.46±9.26, were evaluated. In 59 of 145 patients, 18F-FDG PET/CT was performed;86 patients had gone through 68Ga PSMA PET/CT. Thirty-seven of 145 patients were OM, whereas 108 patients were MM. The median of the SUVmax of metastatic lesions in patients with OM and MM disease in the 18F-FDG group were 5.60 and 9.51, respectively. The results of the calculated median SUVmax values in OM and MM disease in the Ga-68 PSMA group were 13.44 and 29.84, respectively. A significant difference was observed in the median SUVmax results of metastatic lesions between OM and MM disease (p<0.05). Median values of SUVmax calculated from the prostatic site in OM and MM disease were 7.83 and 12.29 respectively in 18F-FDG; 26.23 and 26.74 in the 68Ga PSMA group. No significant difference was found in the SUVmax results of the prostatic site between OM and MM disease (p>0.05). SUVmax results of metastatic lesions are significantly higher in patients with MM than in patients with OM disease in patients with PC, which may be secondary to their different biological contents in terms of aggressiveness.

Prostate-Specific Membrane Antigen PET Positivity in a Lung Mass: Diagnosis of Diffuse Large B-Cell Lymphoma.

An 84-year-old man with nonmetastatic castrate-sensitive prostate cancer was referred for a 68Ga-prostate-specific membrane antigen (PSMA) PET/CT scan with a prostate-specific antigen level of 3.6 ng/mL for restaging. He was 22 years post-radical prostatectomy and had salvage radiation being managed with intermittent hormonal therapy. Imaging revealed a right lower lobe mass with increased PSMA uptake (SUVmax 6.2). Biopsy and subsequent immunostaining determined the mass to be diffuse large B-cell lymphoma. We report a case of diffuse large B-cell lymphoma diagnosed in the setting of PSMA positivity, highlighting awareness for oncologists and radiologists to know this possibility.

Protocol of the integrated boost to the dominant intraprostatic nodule in stereotactic body radiation therapy for localized prostate cancer.

Aim: To explore the safety and efficacy of the integrated boost to the dominant intraprostatic nodule (DIN) based on 68Ga prostate-specific membrane antigen PET/MRI in stereotactic body radiation therapy (SBRT) for patients with localized prostate cancer. Methods: SBRT regimen is employed - namely, sequential integrated boost (SIB) to the DIN based on 68Gaprostate-specific membrane antigen PET/MRI. SIB prescription dose of 36.25 Gy in five fractions to fixed prophylactic tumoricidal region is delivered, followed by 7.25 Gy in one fraction added to the DIN every other day. The primary end point of the study will be toxicity assessed by the Common Terminology Criteria for Adverse Events 5.0 grading scale. Secondary end points include biochemical progression-free survival, local progression-free survival, distant metastasis-free survival and overall survival. Discussion: This trial is to prove the safety and efficacy of sequential integrated boost to the DIN in SBRT. Clinical Trial Registration: NCT04599699 (ClinicalTrials.gov).

Unexpected Metastatic Localizations of Prostate Cancer Determined by 68Ga PSMA PET/CT: Series of Four Cases.

Prostate-specific membrane antigen (PSMA) is a transmembrane protein with overexpression in most prostate cancer cells. Gallium-68-(68Ga) PSMA positron emission tomography/computed tomography (PET/CT) imaging is a game-changer in the management of prostate cancer. 68Ga PSMA PET/CT scan is advanced and a promising radioligand has high sensitivity in determining lesions of prostate cancer with a high tumor to background ratio. The most common areas of metastasis are the bone and pelvic lymph nodes. The prognosis of prostate cancer is mainly determined by the status of metastases. The presence and the localization of metastases affects treatment planning. In our cases, we presented some examples of uncommon sites of metastases such as the brain, adrenal glands, penis and orbit. Improvements in imaging techniques, such as 68Ga PSMA PET/CT have led to the possibility to make more determi nation of rare metastase sites in prostate cancer patients.

Mild 68Ga PSMA-11 Uptake in Incidental Pituitary Adenoma.

A 76-year-old man with metastatic prostate cancer was referred to 68Ga prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) for restaging. A consecutive 18F-fluorodeoxyglucose (FDG) PET/CT was performed due to the history of lung cancer in the left lung treated with stereotactic radiotherapy. Intense 18F-FDG uptake was detected in the pituitary gland despite the mild uptake of 68Ga PSMA. Contrast-enhanced magnetic resonance imaging confirmed pituitary adenoma.

Deriving local diagnostic reference levels for four common adult PET/CT procedures in a Saudi Arabian hospital

ObjectiveTo present the results of a local diagnostic reference level (LDRL) audit for 50th fluorodeoxyglucose (18F-FDG), Gallium-68 etraazacyclododecane tetraacetic acid–octreotide (68Ga-DOTATATE), and 68Ga prostate-specific membrane antigen (68Ga-PSMA) whole-body and 18F-FDG brain imaging positron emission tomography/computed tomography (PET/CT) scans. Materials and methodsPatients who underwent whole-body 18F-FDG (158 patients), brain 18F-FDG (50 patients), 68Ga-PSMA (20 patients) and 68Ga-DOTATATE (24 patients) PET/CT examinations at Prince Sultan Military Hospital in Riyadh, Saudi Arabia were selected for this study. For these patients, related data were collected that included demographic information, radiation dose quantities, PET/CT protocols and scanner specifications. The LDRL value of the radiation dose for each type of scan was determined based on the calculation of the 50th percentile. ResultsThe reported 50th percentile for 18F-FDG for whole-body (307.10 MBq) and brain (280.46 MBq) scans were in good agreement with reported national DRLs (NDRLs). The value of the 50th percentile related to 18F-FDG brain imaging was higher than the 50th percentile identified in the literature. The derived LDRLs for 68Ga-DOTATATE (172.05 MBq) and 68G-PSMA (183.89 MBq) were lower than those in the published Administration of Radioactive Substances Advisory Committee (ARSAC) United Kingdom report of 250 MBq and 200 MBq, respectively. The determined CT dose index volume (CTDIvol) and dose–length product (DLP) for diagnostic CT components associated with whole-body 18F-FDG PET/CT examinations were higher than the published Japanese NDRL and lower than the New Zealand NDRL. However, the derived 50th percentile of 68Ga PET/CT scans was higher than the CT radiation dose associated with a whole-body 18F-FDG PET/CT scan. ConclusionThis study derived the LDRL for four common PET/CT procedures. There is room for lowering the 18F-FDG administered activity with good image quality, despite good agreement with previously published data on NDRLs. It is preferable to optimize the diagnostic CT component associated with all whole-body scans without compromising diagnostic CT image quality.

Salvage Involved-Field and Extended-Field Radiation Therapy in Positron Emission Tomography–Positive Nodal Recurrent Prostate Cancer: Outcomes and Patterns of Failure

PurposeThe optimal salvage pelvic treatment for nodal recurrences in prostate cancer is not yet clearly defined. We aimed to compare outcomes of salvage involved-field radiation therapy (s-IFRT) and salvage extended-field radiation therapy (s-EFRT) for positron emission tomography/computed tomography–positive nodal-recurrent prostate cancer and to analyze patterns of progressions after salvage nodal radiation therapy. Methods and MaterialsPatients with 18F-fluorocholine or 68Ga prostate-specific membrane antigen ligand positron emission tomography/computed tomography–positive nodal-recurrent prostate cancer and treated with s-IFRT or s-EFRT were retrospectively selected. Time to biochemical failure, time to palliative androgen deprivation therapy (ADT), and distant metastasis–free survival were analyzed. ResultsBetween 2009 and 2019, 86 patients were treated with salvage nodal radiation therapy: 38 with s-IFRT and 48 with s-EFRT. After a median follow-up of 41.9 months (5.4-122.1 months), 47 patients presented a further relapse: 31 after s-IFRT and 16 after s-EFRT, with only 1 in-field relapse. The median time to palliative ADT was 24.8 months (95% confidence interval [CI], 13.3-93.5 months) in the s-IFRT group and not yet reached (95% CI, 40.3 months to not yet reached) in the s-EFRT group (P = .010). The 3-year biochemical failure–free rate was 70.2% (95% CI, 51.5%-82.9%) with s-IFRT and 73.9% (95% CI, 55.4%-85.7%) with s-EFRT (P = .657). The 3-year distant metastasis–free survival was 74.1% (95% CI, 56.0%-85.7%) with s-IFRT and 82.0% (95% CI, 63.0%-91.8%) with s-EFRT (P = .338). Conclusionss-EFRT and s-IFRT for positron emission tomography–positive nodal-recurrent prostate cancer provide excellent local control. Time to palliative ADT was longer following s-EFRT than following s-IFRT.

Super Early Scan of PSMA PET/CT in Evaluating Primary and Metastatic Lesions of Prostate Cancer.

68Ga-prostate specific membrane antigen (PSMA)-11 PET/CT has been widely used in the diagnosis of prostate cancer (PCa); however, the urine lead shielding resulting from the urinary metabolism of tracers may obstruct the detection of surrounding metastasis. In this research, the additive value of super early scanning in diagnosing primary lesions and metastasis in the pelvic cavity was evaluated. Firstly, the differentiation efficiency of 68Ga-PSMA-11 PET scanned at 3 min post-injection (min P.I.) was measured in PSMA-positive (22rv1 cells) and PSMA-negative (PC3 cells) model mice. Secondly, 106 patients were scanned at 3 min P.I. for the pelvic cavity and then scanned as a standard protocol at 45 min P.I. In the results, the differential diagnosis of PSMA expression was completely reflected as early as 3 min P.I. for mice models. For patients, when correlated with the Gleason score, the quantitative results of the super early scan displayed a comparable correlation coefficient with the routine scan. The target to bladder ratios increased from 1.44 ± 2.40 at 45 min to 10.10 ± 19.10 at 3 min (p < 0.001) for the primary lesions, and it increased from 0.99 ± 1.88 to 9.27 ± 23.03 for metastasis. Meanwhile, the target to background ratios increased from 2.21 ± 2.44 at 3 min to 19.13 ± 23.93 at 45 min (p < 0.001) for the primary lesions, and it increased from 1.68 ± 2.71 to 12.04 ± 18.73 (p < 0.001) for metastasis. In conclusion, super early scanning of 68Ga-PSMA-11 PET/CT added referable information for metastasis detection in order to avoid disturbing tracer activity in the urinary system.