We thank Dr. Yiu-Tai Li and Wen-Hsun Chang1 for the valuable comments and questions on our study named “Effects of nerve-sparing procedures on surgical margins after robot-assisted radical prostatectomy: a single center cohort study in Taiwan” published in the Journal of the Chinese Medical Association.2 The author comments are discussed below.
There are totally 419 prostate cancer patients underwent robot-assisted radical prostatectomy (RARP) and 2 of them are pathologically T4 stage reported in radical prostatectomy (RP) specimens, so these 2 patients are not included in pT2/T3 stage. Hence, there is a small discrepancy of the number between RP patients and pT2/T3 stage in RP specimens.
According to Table 2, a total of 309 cases received bilateral nerve-sparing (NS) RARP and 90 cases underwent unilateral NS RARP while 20 cases were performed non-NS RARP.2 The sum of percentage not equal to 100% is based on their each group, and that is to say that the patients are categorized into positive and negative margins groups in longitudinal columns based on the types of NS procedures.2 A sum of positive and negative margins is equal to 100% in terms of unilateral, bilateral, and non-NS groups, respectively.2
Indeed, we had compared the difference of the positive surgical margins (PSM) ratio between NS groups (including unilateral and bilateral NS procedures) and non-NS groups, the PSM rate were reported higher in NS groups than in non-NS groups in univariable analysis (29.1% vs 50%; p = 0.047). However, when comparing the NS impact on the PSM rate in multivariable analysis, the p values was 0.742 without reaching a significant difference (odds ratio: 0.825; 95% CI: 0.261–2.602). One reason is a small case number of non-NS groups and the other reason is a high ratio of T3 stage selection in non-NS groups which is a strongly predominant impact factor for PSM after surgery.
The unilateral NS group seems to have a little higher PSM rate than the bilateral NS group, but the percentage of PSM is actually 30.3% and 28.8% separately without reaching a significant difference between these 2 groups. How to explain this tricky phenomenon? The possible explanation is the location of PSM (including posterolateral, bladder neck, apical and multifocal regions), which may not be concordant to the sites of unilateral NS or bilateral NS procedures. Therefore, in our study, we particularly compare the effect of NS procedure which focus on the same laterality of PSM and calculate only the posterolateral region of PSM based on 838 prostate lobes. Thus, this statistical result specifically examines the true effects of NS procedures on surgical margins where the NS techniques were performed.
We hope these explanations will suffice the readers’ and the authors’ expectations. Thanks you for your interest again.
1. Li YT, Chang WH. The impact of nerve sparing robotic-assisted radical prostatectomy on positive surgical margins: Uncertainty. J Chin Med Assoc 2023;86:254.
2. Yang CW, Wang HH, Hassouna MF, Chand M, Huang WJ, Chung HJ. Effects of nerve-sparing procedures on surgical margins after robot-assisted radical prostatectomy. J Chin Med Assoc 2022;85:1131–5.