IP8-FLUORESCE: A Prospective Paired Cohort Study Evaluating the Diagnostic Accuracy of Fluorescence Confocal Microscopy for Real-time Assessment of Surgical Margins in Radical Prostatectomy

Abstract

Background and objective: Positive surgical margins (PSMs) following radical prostatectomy (RP) are linked to adverse oncological outcomes. Intraoperative margin assessment facilitates immediate secondary resection, enabling more men to undergo "nerve-sparing" RP and improving functional outcomes. Existing techniques, however, have not been adopted widely due to inherent limitations. Fluorescence confocal microscopy (FCM) is a more feasible alternative, offering rapid, high-resolution imaging of unprocessed tissue. This study evaluates the diagnostic performance of FCM for detecting PSMs during RP.

Methods: In this multicentre, prospective, blinded, paired cohort study, men undergoing RP for localised or locally advanced prostate cancer were enrolled across three UK uro-oncology centres between August 17, 2023, and September 23, 2024. FCM was performed on fresh prostatectomy specimens using the Histolog scanner. The whole specimen was examined en face with no tissue resection. Final histopathology served as the reference standard. The primary outcome was the diagnostic performance of FCM for PSM detection on a per-patient level, assessed by sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Multiple definitions of PSMs were evaluated. This study was prospectively registered on ISRCTN (21536411).

Key findings and limitations: A total of 156 patients were recruited. The prevalence of all PSMs was 30.8% (48/156). For all lengths of PSMs, including focally positive and <1 mm margins, sensitivity, specificity, PPV, and NPV were 48% (95% confidence interval 33-63%), 94% (88-98%), 79% (60-92%), and 80% (72-87%), respectively. For PSMs of ≥3 mm, FCM demonstrated sensitivity of 79% (54-94%), specificity of 94% (89-97%), PPV of 71% (48-89%), and NPV of 96% (91-99%). Of the false negative cases, 84% were ≤2 mm; 52% were at the apex.

Conclusions and clinical implications: FCM is a feasible, rapid technique for intraoperative margin assessment in RP. Its diagnostic accuracy is reasonable for clinically significant, longer PSMs, but limited for shorter margins, particularly at the apex. These findings support further evaluation in a clinical utility study to determine whether intraoperative FCM can guide surgical decision-making, optimise nerve sparing, and ultimately improve oncological and functional outcomes.

Keywords: Fluorescence confocal microscopy; Intraoperative margin assessment; Positive surgical margins; Prostate cancer; Radical prostatectomy; Robotic surgery.