Optimized application of 68Ga-prostate-specific membrane antigen-617 whole-body PET/CT and pelvic PET/MR in prostate cancer initial diagnosis and staging

Abstract

Purpose To analyze 68Ga-PSMA-617 PET/CT or PET/MR and delayed PET/MR images in patients diagnosed with or suspected of prostate cancer, and to explore the optimal use of PET/CT and PET/MR for initial diagnosis and staging in prostate diseases.Methods Images from conventional scan by 68Ga-PSMA whole-body PET/CT or PET/MR followed by delayed pelvic PET/MR were retrospectively analyzed. Prostatic 68Ga-PSMA uptake was measured as SUVmax1 (conventional scan 1 h post injection) and SUVmax2 (delayed scan 3 h post injection). Age, PSA levels, and SUVmax were compared between benign and malignant cases. The correlation of SUVmax1 and SUVmax 2 was analyzed. Diagnostic performance was evaluated by ROC analysis.Results We enrolled 56 patients with 41 malignant and 15 benign prostate lesions. Fifty-three patients had paired conventional and delayed scans. Age, PSA levels, and SUVmax were significantly different between benign and malignant cases. A good correlation was found between SUVmax1 and SUVmax2. There was significant difference between SUVmax1 and SUVmax2 in the malignant group (p = 0.001). SUVmax1 had superior diagnostic performance than SUVmax2, SUVmax difference and PSA levels, with a sensitivity of 85.4%, a specificity of 100% and an AUC of 0.956. A combination of SUVmax1 with nodal and/or distant metastases and MR PIRADS V2 score had a sensitivity and specificity of 100%. Delayed pelvic PET/MR imaging in 33 patients were found to be redundant because these patients had nodal and/or distant metastases which can be easily detected by PET/CT.Conclusion Combined 68Ga-PSMA whole-body PET/CT and pelvic PET/MR can accurately differentiate benign prostate diseases from prostate cancer and accurately stage prostate cancer. Whole-body PET/CT is sufficient for advanced prostate cancer, and more economic and time-saving than PET/MR. Pelvic PET/MR contributes to diagnosis and accurate staging in early prostate cancer. Imaging at about 1 hour after injection is sufficient in most patients.Trial registration: NCT03756077. Registered 27 November 2018 - Retrospectively registered, https://clinicaltrials.gov/show/NCT03756077