PP12 Presentation Time: 11:20 AM: Prognostic Factors of Outcomes in Prostate Cancer Patients Treated with Permanent Implant: A High-Volume Center Experience

Abstract

<h3>Purpose</h3> This study aims to report prognostic factors of clinical outcomes of prostate cancer (PCa) patients treated with permanent implant prostate brachytherapy (PIPB) at our institution. <h3>Materials and Methods</h3> The study sample consists of 2364 PCa patients treated with PIPB with or without cytoreductive antiandrogen therapy (ADT) between 1994 and 2020. Kaplan-Meier analyses with log-rank tests were performed to assess and compare biochemical relapse (BCR) according to risk stratification factors, dosimetry parameters or physician performing the implant. Univariate and multivariate Cox regression models were used to identify significative prognostic factors for BCR. <h3>Results</h3> The mean age of the patients at treatment time was 63.7±6.9 years. The median follow-up time was 81 months. Most patients had low-risk clinical features with 73.9% having Gleason score under or equal to 6, 92.6% a pre-treatment PSA value under 10, and 93.4% a clinical stage of T2A or lesser. 30.4% of patients were prescribed ADT. The 5 and 10 years BCR-free survival were 95.4 and 90.1%, respectively. Four physicians (RO) with different clinical experience have performed more than 150 PIPB procedures at our institution: 171, 1099, 805 and 240 cases, respectively for RO1 to RO4. On Kaplan-Meier analysis, the four ROs obtained 80.3, 88.5, 93.5 and 87.0 % 10 years BCR-free survival, respectively. When stratifying patients by D'Amico risk groups, no significative difference was found between ROs on log-rank tests. On univariate Cox model, RO1 (HR=3.43, 95%CI: 1.98-5.92) and RO2 (HR=1.85, 95%CI: 1.23-2.79) had significantly higher hazard ratios than RO3. When correcting for different risk stratification factors in multivariate Cox models, only pre-treatment PSA level (HR=1.11, 95%CI: 1.073-1.148, p<0.001) and ADT use (HR=2.179, 95%CI: 1.524-3.116, p<0.001) were identified as prognostic factors for BCR, but the experience of the RO performing the procedure (p=0.258), clinical stage (p=0.135), age (p=0.166) and dosimetry parameters (D90, p=0.121; V100, p=0.312) were not. <h3>Conclusions</h3> The 26 years' experience of PIPB at our institution shows a five, ten years and all-time BCR-free survival of 95.4, 90.1 and 80.4%, respectively, with the latest failure occurring 18 years after treatment. The most important prognostic factor identified in our cohort of patients were pre-treatment PSA level and ADT usage. Whereas clinical tumor stage, patients' age, dosimetry parameters or RO experience were not found to be significant.