BERKELEY, CA (UroToday.com) - Positive surgical margin (PSM) in radical prostatectomy (RP) specimens is also one of the most important predictive factors for biochemical recurrence (BCR), local recurrence, and the development of distant metastases. In the past 2 decades, with an increase in prostate-specific antigen (PSA) testing and improvement of surgical techniques, the rate of PSM has been reduced considerably. Several studies have evaluated preoperative factors in association with margin status after robot-assisted RP (RARP). To the best of our knowledge, no studies have addressed clinical preoperative predictive factors for PSM after RARP in Japanese patients.
The present study was undertaken to identify preoperative factors for predicting PSM in Japanese patients who underwent RARP performed by a single surgeon.
Between August 2006 and September 2011, a cohort of 244 men underwent RARP, performed by a single surgeon with considerable expertise in open RP (about 500 surgeries performed), but limited laparoscopic skills. We assessed the preoperative factors in these patients for predicting PSMs after RARP. The preoperative variables included age, body mass index, PSA level, PSA density, clinical T stage, prostate volume, surgeon volume, number of positive cores, and percentage of positive cores.
Surgical Technique and Pathological Analyses
All procedures were performed using a transperitoneal, 6-port technique, based on a previously established method. In general, a nerve-sparing procedure was recommended to patients with cT1c-cT2a and biopsy Gleason score of 7 or less. The inter-facial nerve sparing procedure was performed athermally, with an early retrograde release of the neurovascular bundles before ligation of the prostatic pedicles. Although many patients were referred from other hospitals, all biopsy specimens taken in other hospitals were examined at our institution. PSM was defined as the tumor extension into the inked surface of the resected specimen.
Statistical Analyses
Univariate and multivariate logistic regression analyses were performed to identify clinical covariates significantly associated with an increased PSM. Independence of fit of categorical data was analyzed by the chi-square test. Independent factors for the prediction of PSM were identified by a stepwise logistic regression analysis. In this analysis, we included both continuous variables and categorical variables. The predicted probability of PSM was estimated with the formula p = 1 / (1 + exp (-k)). Logistic regression produces a score of k, where k = a + b1 X 1 + b2 X 2, which is a linear combination of the predictors (X 1, X 2) in the model.
In the univariate analyses, serum PSA level, PSA density, and surgeon volume were significantly associated with PSM. In the multivariate analysis, PSA density (hazard ratio (HR), 3.13; 95% confidence interval (CI), 1.57–6.24; p = 0.001) and surgeon volume (HR, 2.15; 95% CI, 1.06–4.35; p = 0.034) were independent predictive factors for PSM. By using these 2 independent factors obtained from multivariate analysis, the predicted probability of PSM was estimated with the formula, p = 1 / (1+exp (-k)).The k of this model was calculated as follows: k = 1.401 + 0.765 × (surgeon volume) - 1.140 × (PSA density). In this equation, surgeon volume was equal to 1 when the surgeon volume was ≤ 50 and was equal to 0 when the surgeon volume was ≥ 51. PSA density was equal to 1 when PSA density was ≥ 0.2 and equal to 0 when PSA density was < 0.2. We divided the patients into 4 groups and calculated the predictive probability of PSM. The predictive probability for PSM in each group was well correlated with the observed rates at 10.8% and 10.2%, 19.8% and 20.0%, 26.4% and 26.4%, 43.5% and 43.3%, respectively(regression coefficient = 0.9995, p < 0.0001).
To the best of our knowledge, this is the first report evaluating the incidence of PSM and preoperative predictive factors of PSM in Japanese patients treated with RARP. PSA density and surgeon volume were independent factors for predicting PSM after RARP in Japanese patients, and a combination of these 2 factors may be useful for predicting PSM in patients with prostate cancer undergoing RARP.
Written by:
Takeshi Hashimoto, Kunihiko Yoshioka, Jun Nakashima, and Masaaki Tachibana as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Urology, Tokyo Medical University, Tokyo, Japan
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