18 F-Fluciclovine PET/MRI for preoperative lymph node staging in high-risk prostate cancer patients

Objective To investigate the diagnostic potential of simultaneous 18 F-fluciclovine PET/MRI for pelvic lymph node (LN) staging in patients with high-risk prostate cancer. Methods High-risk prostate cancer patients (n=28) underwent simultaneous 18 F-fluciclovine PET/MRI prior to surgery. LNs were removed according to a predefined template of eight regions. PET and MR images were evaluated for presence of LN metastases according to these regions. Sensitivity/specificity for detection of LN metastases were calculated on patient and region basis. Sizes of LN metastases in regions with positive and negative imaging findings were compared with linear mixed models. Clinical parameters of PET-positive and -negative stage N1 patients were compared with the Mann-Whitney U test. Results Patient- and region-based sensitivity/specificity for detection of pelvic LN metastases was 40 %/87.5 % and 35 %/95.7 %, respectively, for MRI and 40 %/100 % and 30 %/100 %, respectively, for PET. LN metastases in true-positive regions were significantly larger than metastases in false-negative regions. PET-positive stage N1 patients had higher metastatic burden than PET-negative N1 patients. Conclusion Simultaneous 18 F-fluciclovine PET/MRI provides high specificity but low sensitivity for detection of LN metastases in high-risk prostate cancer patients. 18 F-Fluciclovine PET/MRI scan positive for LN metastases indicates higher metastatic burden than negative scan. Key Points • 18 F-Fluciclovine PET/MRI has high specificity for detection of lymph node metastasis. • 18 F-Fluciclovine PET/MRI lacks sensitivity to replace ePLND. • 18 F-Fluciclovine PET/MRI may be used to aid surgery and select adjuvant therapy. • 18 F-Fluciclovine PET-positive patients have more extensive disease than PET-negative patients. • Size of metastatic lymph nodes is an important factor for detection.