Diagnostic performance of 18F-fluciclovine PET/CT for regional lymph node metastases in patients with primary prostate cancer: a multicenter phase II clinical trial

Objective: This multicenter, phase II clinical trial evaluated the diagnostic performance of 18F-fluciclovine, a novel amino acid for positron-emission tomography (PET), for detection of small lymph node metastases with short-axis diameters of 5-10 mm in patients with prostate cancer.

Methods: Patients with prostate cancer were eligible after screening of laboratory tests and pelvic contrast-enhanced computed tomography (CT). Pelvic region 18F-fluciclovine PET/CT was then acquired within 28 days and dissection of regional lymph nodes was performed within 60 days of pelvic contrast-enhanced CT. Diagnostic performance of 18F-fluciclovine-PET/CT was evaluated by comparison with standard histopathology of lymph nodes.

Results: In a total of 28 patients, 40 regional lymph nodes with short-axis diameters of 5-10 mm were eligible for efficacy evaluation; seven of these showed metastases confirmed by histopathology. The sensitivity of 18F-fluciclovine PET/CT was 57.1% (4/7). All four true positive lymph nodes detected by 18F-fluciclovine PET/CT had a metastatic lesion with a long-axis diameter of ≥7 mm and a high proportion of cancer volume (60-100%) according to pathology evaluation. The specificity, diagnostic accuracy, positive predictive value, and negative predictive value of 18F-fluciclovine PET/CT in lymph node-based analysis were 84.8% (28/33), 80.0% (32/40), 44.4% (4/9), and 90.3% (28/31), respectively. No clinically significant adverse events occurred.

Conclusions: 18F-fluciclovine PET/CT detected small lymph node metastases; however it also showed positive findings in benign lymph nodes. Refinement of the image assessment criteria may improve the diagnostic performance of 18F-fluciclovine PET/CT for small lymph node metastases in patients with prostate cancer.