Preoperative staging in high-risk prostate cancer patients using [¹⁸F] fluciclovine PET/CT

Objectives: To assess the diagnostic ability of [¹⁸F]fluciclovine PET/CT for preoperative nodal staging in patients with high risk prostate cancer and presumed localized disease.

Methods: 45 patients with high risk prostate cancer, negative bone scan and clinically localized disease on conventional imaging scheduled for robotic radical prostatectomy with extended pelvic lymph node dissection underwent [¹⁸F]fluciclovine PET/CT. Histologic confirmation of metastasis was considered primary standard of truth in those eligible for surgery, while serial imaging and clinical response was the reference for those ineligible for surgery (secondary standard of truth). Measures of diagnostic performance of fluciclovine PET/CT for metastatic disease were determined on a per patient level, region level (right pelvic, left pelvic, presacral and extraregional groups of lymph nodes) and surgical template level (right and left common, internal and external iliac, right and left obturator, and right and left presciatic, presacral, and extraregional lymph nodes).

Results: 42/45 patients underwent surgery, 3/45 had androgen deprivation therapy ± radiotherapy after PET/CT. Mean PSA was 27.5±31.4 ng/ml, and median Gleason score (Grade group) was 9 (5). All patients had fluciclovine uptake in the prostate. Truth was confirmed by histology, primary reference standard, in 43/45 (95.6%) patients (42 surgery, 1 nodal biopsy), while serial imaging and clinical response was reference for truth, secondary reference standard, in 2/45 patients. PET-CT detected metastatic disease (N₁±M₁) in 18/45 (40%) patients. Metastatic disease was confirmed in 26/45 (57.8%) patients (24/45 patients confirmed by primary reference standard, 2/45 confirmed by secondary reference standard). Fluciclovine PET/CT correctly detected metastatic disease in 16/26 patients. 11/26 patients with metastatis had extraregional (M₁) metastasis (paraaortic, paracaval, mesenteric, perirectal, perivesical lymph nodes ± bone metastasis), 8 of the 11 patients were correctly detected by fluciclovine PET/CT. Patient based (n=45) sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for metastatic prostatic disease were 61.5%, 89.5%, 88.9% and 63.0% respectively. For patients who had surgery (n=42), sensitivity at the region level (n=42x4 regions) was 56.3%, specificity 98.3%, PPV 93.1% and NPV 84.9%. On the surgical template level (n=42x12 templates), the sensitivity, specificity, PPV and NPV were 45.2%, 99.5%, 94.3% and 91.5% respectively.

Conclusions: Fluciclovine PET-CT appears to be a valuable tool for pre-operative staging of patients with high-risk prostate cancer with a high specificity for detection of metastatic disease. Fluciclovine PET-CT may help in decision-making for treatment options and help guide lymph node dissection during surgery. $$graphic_AC9A0724-0341-4787-879E-B778011EFFAB$$

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