Objective: To explore and identify the associated risk factors contributing to positive surgical margins after open radical
prostatectomy (ORP), laparoscopic radical prostatectomy (LRP), and robotic-assisted radical prostatectomy (RARP) in a highvolume tertiary center of Thailand.

Materials and Methods: From January 2013 to September 2019, the data of 1,070 prostate cancer patients treated with ORP, LRP, and RARP were retrospectively studied. After excluding cases with pathologically positive lymph nodes, the remaining 995 patients were categorized into 2 groups: one with PSMs and one without PSM. The data of both groups were evaluated using independent t-test, Mann–Whitney U-test, Pearson’s Chi-squared test, and univariate and multivariate analyses.

Results: Of the 995 patients, 575 patients (57.8%) had PSMs. Oncologic factors (prostate specific antigen [PSA], prostate weight, percentage of tumor volume, pathologic T stage [pT], and ISUP Gleason Grade Group) were significantly different between the two groups. Meanwhile, patient factors (age and body mass index) and surgical factors (ORP, LRP, RARP, surgeon experience, and nerve sparing) were not significantly different. By multivariate logistic regression analysis, the independent factors associated with the
occurrence of PSM were PSA >10 (odds ratio [OR]: 1.65; 95% confidence interval [CI]: 1.16 to 2.34; p = 0.005), prostate weight (OR: 0.99; 95% CI: 0.98 to 0.99; p = 0.003), tumor volume >50% (OR: 3.43; 95% CI: 1.48 to 7.95; p = 0.004), pT3 (OR: 2.34; 95% CI: 1.68 to 3.25; p<0.001), and ISUP Gleason Grade Group >1 (p<0.05).

Conclusion: The independent factors associated with PSM after radical prostatectomy were the oncologic factors, which were PSA, prostate weight (small prostate), percentage of tumor volume, pT, and ISUP Gleason Grade Group. On the contrary, patient factors (age and BMI) and surgical factors (surgical procedure, surgeon experience, and nerve sparing) were found to be unassociated with PSM.

Keywords: Prostate cancer, Radical prostatectomy, Positive surgical margins, Associated factors, Risk factors, Predictive factors