[18F]fluciclovine PET/CT versus multiparametric MRI assessment of seminal vesicle invasion and extracapsular extension in patients with primary prostate cancer.

Introduction: Accurate preoperative detection of seminal vesicle invasion (SVI) and extracapsular extension (ECE) in patients with prostate cancer is important for treatment planning. Conventional imaging, including MRI has limitations. Molecular imaging is being increasingly utilized for preoperative evaluation of patients with high-risk prostate cancer. We set out to compare the diagnostic performance of [18F]fluciclovine PET/CT and multiparameteric MRI (mpMRI) for the preoperative detection of SVI and ECE in patients with unfavorable intermediate to very high-risk prostate cancer. Materials and Methods: Thirty-five men diagnosed with unfavorable intermediate to very high-risk prostate cancer and no evidence of systemic metastasis on conventional imaging, deemed eligible for potential curative surgery underwent fluciclovine PET/CT and standard of care mpMRI followed by robotic radical prostatectomy with extended pelvic lymph nodes dissection. Interpretation of MRI was done per institutional standards and reports of SVI and ECE noted. Fluciclovine PET/CT interpretation was done by a board certified Nuclear Radiologist with over 20 years’ experience; abnormal uptake indicating the presence of SVI and ECE was recorded. Histologic confirmation of SVI and/or ECE was reference standard of truth. Measures of diagnostic performance (sensitivity, specificity, positive predictive value and negative predictive value, with the corresponding score 95% confidence interval (95%CI) were assessed for fluciclovine PET/CT and mpMRI and compared using McNemar's and generalized score tests. Statistical significance was set at p<0.05.

Results: Median PSA was 11.3 ng/ml (range: 2.49-97.37 ng/ml) and the median Gleason score (Grade group) was 9 (5). On fluciclovine PET-CT, 19/35 (54.3%) and 15/35 (42.9%) patients were interpreted as positive for SVI and ECE respectively, while on mpMRI, 9/35 (25.7%) and 13/35 (37.1%) patients were interpreted as positive for SVI and ECE respectively on. Histology confirmed SVI and ECE in 16/35 (45.7%) and 29/35 (82.9%) patients respectively. For SVI detection PET/CT versus mpMRI on per patient analysis had sensitivity, and specificity of 68.8% vs 37.5% (p = 0.125), and 57.9% vs 89.5% (p = 0.109), respectively. For PET/CT versus mpMRI in ECE detection, sensitivity, and specificity were 48.3% vs 44.8% (p =1.00), and 83.3% vs 100% (p = 1.00), respectively. (see table)

Conclusions: There is no significant difference between the ability of [18F]fluciclovine PET/CT and multiparametric MRI in the local staging of prostate cancer in patients with intermediate to very high-risk prostate cancer. Fluciclovine PET/CT has a higher sensitivity for detection of SVI compared to mpMRI, while MRI has higher specificity, in a non-significant trend. The ability of fluciclovine PET to detect ECE is comparable to multiparametric MRI. Larger prospective studies are required to further evaluate this trend.

• Download figure
• Open in new tab
• Download powerpoint