Background: PSMA PET is a promising method for primary lymph node staging in prostate cancer. However, recent systematic reviews have identified only a limited number of studies with histopathology as a reference test. Methods: A systematic search was performed in PubMed and the Cochrane Library. An expedited systematic review was performed where we identified diagnostic studies in prostate cancer where a preoperative PSMA PET for primary lymph node staging was compared to histopathology. The trials must have diagnostic data on a patient level. Results: Eighteen eligible clinical trials included 969 patients. The median patient number per study was 32 (range 10 to 208). Five trials were prospective, and nine trials had a consecutive enrolment of patients. Sixteen studies used Ga-68-PSMA-11; there was one study with Cu-64-PSMA and one study with F-18-DCDFPyL. Twelve studies used PET/CT, four trials used PET/MR. Most trials included patients with intermediate and high-risk. Diagnostic accuracy varied notably among the studies; sensitivity ranged from 23 to 100%, specificity 67–100%, positive predictive value 20–100%, and negative predictive value 41–100%. Weighted sensitivity was 59%, weighted specificity was 93%. Four studies compared PSMA PET with anatomical imaging (CT or MRI); in all cases, sensitivity and specificity were superior with PSMA PET. Three studies compared PSMA PET with multi-parametric or diffusion-weighted MRI with mixed results. Conclusions: PSMA PET showed promising diagnostic accuracy for primary lymph node staging with pathology as reference. Recommendation for PSMA PET for high-risk patients in clinical guidelines should be supported by confirmatory, prospective trials with patient-relevant outcomes.

Background: The diagnostic value of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) as the first imaging approach in the evaluation of rising carcinoembryonic antigen (CEA) is not clear. The objective of this study was to investigate the value of ¹⁸F-FDG PET/CT in patients with colorectal cancer (CRC) and suspected recurrence based on rising CEA. Methods: A total of 73 patients with CRC were referred to PET/CT after radical surgery. Generally, all patients were scheduled to follow a CT-based post-surgical follow-up regimen. In the case of rising CEA, ¹⁸F-FDG PET/CT was performed in most patients with contrast-enhanced CT. The PET/CT images were independently reviewed by two readers. The presence or absence of recurrence was based on histology and/or standardized clinical follow-up. Results: Among 35 patients who had confirmed recurrence of CRC, PET/CT demonstrated recurrence with a sensitivity of 85.7 %, a specificity of 94.7 %, a positive predictive value of 93.8 %, and a negative predictive value of 87.8 %. The SUV_max ranged from 1.3 to 19.9. The mean time since the last postoperative imaging and PET/CT was 8 months (median 4 months). CEA values at referral ranged from 1.5 to 164.0 μg/L (median 5.6 μg/L). The diagnostic properties of PET/CT were analyzed in subgroups of patients with a single rising CEA sample (30 patients, 41 %), 31 patients (43 %) with two or more consecutive increases, and 12 patients (16 %) with persistently elevated values. Conclusions: ¹⁸F-FDG PET/contrast-enhanced CT has high diagnostic accuracy in the diagnosis of recurrent CRC, even in patients in a conventional CT-based follow-up program.

Both ^99mTc-DTPA and ⁵¹Cr-EDTA are widely used to determine glomerular filtration rate (GFR), but few direct comparative studies exist. The shortage of ⁵¹Cr-EDTA makes a direct comparison highly relevant. The aim of the study was to investigate if there is any clinically relevant difference between plasma clearance of ^99mTc-DTPA and ⁵¹Cr-EDTA. Patients ≥18 years of age referred for routine GFR measurement by ⁵¹Cr-EDTA were prospectively enrolled. The two tracers (10 MBq ^99mTc-DTPA (CaNa₃-DTPA) and 2.5 MBq ⁵¹Cr-EDTA) were intravenously injected at time zero. A standard 4-sample technique was applied with samples collected at 180, 200, 220 and 240 min, if the estimated GFR (eGFR) was ≥30 mL/min. A comparison of single-sample GFR based on the 200 min sample was also conducted. Fifty-six patients were enrolled in the study. All patients had an estimated GFR >30 mL/min/1.73 m². No patients suffered from ascites or significant oedema. The mean ⁵¹Cr-EDTA plasma clearance was 82 mL/min (range 16–226). The plasma clearances determined by the two methods were highly correlated (r = 0.993). The plasma clearance was significantly higher when measured by ^99mTc-DTPA than by ⁵¹Cr-EDTA (p = 0.01), but the numerical difference was minimal (mean difference 1.4 mL/min; 95% limits of agreement (LOA) –6.6 to 9.4). The difference between the two methods was independent of the level of renal function. Similar results were found for one-sample GFR. No clinically relevant differences were found between the plasma clearance of ^99mTc-DTPA and that of ⁵¹Cr-EDTA. Therefore, ^99mTc-DTPA can replace ⁵¹Cr-EDTA when needed.