Staging 68 Ga-PSMA PET/CT in 963 consecutive patients with newly diagnosed prostate cancer: incidence and characterization of skeletal involvement

PURPOSE

The aim of the study was to elaborate the incidence and type of skeletal involvement in a large cohort of patients with newly diagnosed prostate cancer (PCa) referred for Ga-68 PSMA-11 PET/CT staging in a single center.

METHODS

Study cohort included 963 consecutive patients with newly diagnosed PCa referred for Ga-68 PSMA-11 PET/CT study for staging. The incidence of bone involvement, type of bone metastases, and extent of disease were determined and correlated with the ISUP Grade Group (GG) criteria and PSA levels.

RESULTS

Bone metastases were found in 188 (19.5%) of 963 patients. Bone metastases were found in 10.7% of patients with PSA < 10 ng/dL and in 27.4% of patients with PSA > 10 ng/dL and in 6.1% of patients with GG ≤ 2/3 and in 8.9% of patients with GG 4/5. In 7.6% of the patients, skeletal involvement was extensive, while 11.9% of patients had oligometastatic disease. Osteoblastic type metastases were the most common type of bone metastases presented in 133 of the patients with malignant bone involvement (70.7%). More than half of them had only osteoblastic lesions (72 patients (38.3%)), while the other (61 patients (32.5%)) had also intramedullary and/or osteolytic type lesions. Intramedullary metastases were found in 97 patients (51.6%), while 41 (21.8%) of them were only intramedullary lesions. Osteolytic metastases were detected in 36 patients (19.2%), of which 8 were only osteolytic lesions.

CONCLUSION

Although traditionally bone metastases of PCa are considered osteoblastic, osteolytic and intramedullary metastases are common, as identified on PET with labeled PSMA. Skeletal spread may be present also in patients with GG ≤ 2/3 and PSA < 10 ng/dL.

Ga-68 PSMA PET/CT in recurrent high-grade gliomas: evaluating PSMA expression in vivo

PURPOSE

We planned this prospective study to evaluate PSMA expression in recurrent high-grade gliomas (rHGG), including anaplastic astrocytoma and glioblastoma using Glu-NH-CO-NH-Lys-(Ahx)-[Ga-68 (HBED-CC)]- (Ga-68 PSMA) positron emission tomography (PET), with its theranostic potential in mind.

METHODS

This was a prospective study enrolling patients with clinical and MRI evidence of rHGG on follow-up. Three treated cases of HGG with RN on MRI were also included as negative controls. Abnormal tracer accumulation in the brain parenchyma, more than the contralateral hemisphere was interpreted as positive study. For semiquantitative analysis, a 3D spherical region of interest (ROI) was drawn around the site of the abnormal Ga-68 PSMA uptake, and the ratio of SUVmax of tumor (T) to SUVmax of the contralateral corresponding area (TBR) was calculated. Each patients' PSMA brain PET was fused to the corresponding MRI and reviewed for concordance.

RESULTS

Thirty patients were included in the study, a total of 49 lesions were detected on MRI, and fused PET/MR images showed increased Ga-68 PSMA uptake in all these lesions. Multifocal lesions were better appreciated on fused PET-MR images, and concordance between MRI and PET was 100 % for patient and lesion-wise detection. Recurrent glioma lesions showed SUVmax and SUVmean values (median and IQR) 6.0 (4.4-8.2) and 3.3 (2.8-3.7), respectively. Lesions labeled as radiation necrosis on MRI did not show tracer accumulation.

CONCLUSION

Ga-68 PSMA has potential utility for evaluating recurrence in HGG and its potential for theranostics would encourage its use in the evaluation of these patients.

Positron emission tomography/computed tomography guided percutaneous biopsies of Ga-68 avid lesions using an automated robotic arm

PURPOSE

The purpose of this prospective study was to evaluate the feasibility of positron emission tomography/computed tomography (PET/CT)-guided biopsy of Ga-68 avid lesions using an automated robotic arm and determine the diagnostic yield of this technique.

MATERIAL AND METHODS

Patients who underwent Ga-68 labelled tracers imaging followed by PET/CT-guided biopsies of tracer-avid lesions were prospectively included. Biopsies were performed using a dedicated automated-robotic-arm assisted PET/CT-guided biopsy device on the same-day of diagnostic PET/CT-imaging. The tissue samples were retrieved after confirming the position of needle-tip in the target lesion. Procedure-related complications and radiation exposure of the interventionist were recorded. Histopathological reports were reviewed for diagnostic yield.

RESULTS

A total of 25 patients (19 men, six women) with a mean age of 50.8±17.3 (SD) years (range: 17-83 years) were included. The biopsies were performed after PET/CT using Ga-68 DOTANOC (n=16) or Ga-68 PSMA (n=8) and Ga-68 chemokine-analogue (n=1). The biopsy samples were obtained from the liver (n=9), bone (n=8), lymph-nodes (n=3), lung (n=1), pancreas (n=1), anterior mediastinal lesion (n=1), peritoneal-deposit (n=1) and thigh-lesion (n=1). No immediate or delayed procedure-related complications were documented in any patient. PET/CT-guided molecular sampling was technically successful in all the patients. Histopathology revealed malignancies in all the biopsied specimens without the need for repeat sampling or further invasive-diagnostic workup, with a diagnostic yield of 100%. The estimated absorbed-radiation dose was 566.7μSv/year for the interventionist.

CONCLUSION

PET/CT-guided molecular biopsy using Ga-68 labelled radiotracers is feasible and can be performed safely and accurately with a high-diagnostic yield. It is helpful in accurately staging the disease when tracer-avid isolated distant lesion evident on imaging and highly practical in patients with previous inconclusive sampling.

Performance evaluation of Cerenkov luminescence imaging: a comparison of 68Ga with 18F

BACKGROUND

Cerenkov Luminescence Imaging (CLI) is an emerging technology for intraoperative margin assessment. Previous research only evaluated radionuclide 18-Fluorine (¹⁸F); however, for future applications in prostate cancer, 68-Gallium (⁶⁸Ga) seems more suitable, given its higher positron energy. Theoretical calculations predict that ⁶⁸Ga should offer a higher signal-to-noise ratio than ¹⁸F; this is the first experimental confirmation. The aim of this study is to investigate the technical performance of CLI by comparing ⁶⁸Ga to ¹⁸F.

RESULTS

The linearity of the system, detection limit, spatial resolution, and uniformity were determined with the LightPath imaging system. All experiments were conducted with clinically relevant activity levels in vitro, using dedicated phantoms. For both radionuclides, a linear relationship between the activity concentration and detected light yield was observed (R² = 0.99). ⁶⁸Ga showed approximately 22 times more detectable Cerenkov signal compared to ¹⁸F. The detectable activity concentration after a 120 s exposure time and 2 × 2 binning of ¹⁸F was 23.7 kBq/mL and 1.2 kBq/mL for ⁶⁸Ga. The spatial resolution was 1.31 mm for ¹⁸F and 1.40 mm for ⁶⁸Ga. The coefficient of variance of the uniformity phantom was 0.07 for the central field of view.

CONCLUSION

⁶⁸Ga was superior over ¹⁸F in terms of light yield and minimal detection limit. However, as could be expected, the resolution was 0.1 mm less for ⁶⁸Ga. Given the clinical constraints of an acquisition time less than 120 s and a spatial resolution < 2 mm, CLI for intraoperative margin assessment using ⁶⁸Ga could be feasible.

Comparison of Ga-68 PSMA positron emission tomography/computerized tomography with Tc-99m MDP bone scan in prostate cancer patients

Background/aim

The aim of our study was to compare Tc-99m MDP bone scan and Ga-68 PSMA PET/CT in terms of detection of bone metastasis in prostate cancer patients.

Materials and methods

A total of 28 prostate cancer patients with bone scan and PSMA PET/CT performed within 90 days were retrospectively included in our analysis. All bone lesions were scored as negative (score-0), positive (score-1), or suspicious (score-2) for metastasis by two experienced nuclear medicine physicians. Both patient-based and region-based analyses were made for all osseous lesions.

Results

On per-patient analysis; sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 72.7%, 52.9%, 50%, 75%, and 60.7%, respectively, for bone scan and 90.9%, 100%, 100%, 94.4%, and 96.4%, respectively, for PSMA PET/CT. On per-region analysis; sensitivity, specificity, PPV, NPV, and accuracy were 76.2%, 80.9%, 57.1%, 91.1%, and 79.8%, respectively, for bone scan and 85.7%, 100%, 100%, 95.5%, and 95.4%, respectively, for PSMA PET/CT.

Conclusion

Ga-68 PSMA PET/CT has higher sensitivity, specificity, and accuracy compared to bone scan in terms of bone metastasis detection in prostate cancer patients. Therefore, it might be the modality of choice for patients with suspicion for metastatic disease, despite negative bone scan and conventional imaging results.