The perineural invasion paradox: Is perineural invasion an independent prognostic indicator of biochemical recurrence risk in patients with pT2N0 prostate cancer?

6 Background: Perineural invasion is a histologic feature present in approximately 19% of patients with prostate cancer. The prognostic significance of perineural invasion is controversial with recent studies yielding contradictory results. This study aims to assess whether perineural invasion on surgical pathology of patients with pT2N0 disease is an independent prognostic indicator of the risk of biochemical recurrence. Methods: We identified 201 patients with non-metastatic pT2N0 prostate cancer at our institution between 1/1/2008-12/31/2014. We reviewed the electronic medical record of these patients and identified whether the patient had biochemical recurrence (defined as PSA > 0.2 after surgery). A multivariable analysis was then performed using clinical and histological data for each patient to assess the association between perineural invasion and biochemical recurrence. Results: Of the 201 patients identified, 68.1% (137/201) had perineural invasion and 14% (28/201) had biochemical recurrence. Perineural invasion was associated with pT2c disease (p < 0.001), an increased number of positive cores on biopsy (p < 0.001), and a higher surgical Gleason score (p < 0.001). 19% of patients with perineural invasion had disease recurrence compared to 3.1% without perineural invasion (p = 0.001, Hazard ratio of 6.2). After performing a multivariable analysis and accounting for pathologic tumor staging and Gleason score, perineural invasion had a trend towards a significant association with recurrence (p = 0.085, Hazard ratio of 3.2). Conclusions: Perineural invasion may be an indicator of unfavorable histology such as a high Gleason score or more widespread disease rather than an independent prognostic indicator of the risk of biochemical recurrence.