Risk factors and risk-stratification model of biochemical failure in patients with positive surgical margin after robot-assisted radical prostatectomy.

The purpose of this study was investigating the risk factors of biochemical failure in cases with positive surgical margins after robot-assisted radical prostatectomy (RARP). We identified 630 cases of RARP that had been performed in a single institution from November 2011 to December 2017. A total of 145 cases showed positive surgical margin after RARP. After excluding patients that had undergone adjuvant therapies (androgen deprivation or radiation), 114 cases were evaluated. Clinical and pathological parameters were investigated in this cohort and were analyzed to identify factors predicting biochemical failure. Subsequently, we developed a risk classification based on these risk factors. The median values of PSA, age, preoperative prostate volume, were 67 (internal quartile range [IQR]: 65-72) years, 9.3 (6.5-12.0) ng/mL, and 37 (25-45) cm³, respectively. There were 53 and 61 patients with pT2 and pT3, respectively. The International Society of Urological Pathology grade group at surgical margin (SM) ≥ 5 (hazard ratio [HR] 3.37, 95% confidence interval [CI] 1.48-7.68), and max length of cancer at SM ≥ 4 mm (HR 2.59, 95% CI 1.27-5.32), and nadir PSA ≥ 0.03 (HR 8.66, 95% CI 4.66-16.1) were identified as factors predicting biochemical failure. Subsequently, a risk-stratification model was developed using these factors. The model showed a C index of 0.801. This study identified risk factors predicting biochemical failure in patients with positive surgical margins after RARP.