The Results of Adjuvant and Salvage Radiotherapy Following Radical Prostatectomy

Abstract

Objective:The aim of the study is to evaluate the contribution of postoperative adjuvant radiotherapy (ART) and salvage radiotherapy (SRT) to oncological outcomes and side effects related to treatment in prostate cancer patients with adverse prognostic factors.Method:Between January 2000 and January 2020, 105 patients who received the diagnosis of prostate cancer and underwent ART or SRT in our clinic after open or robotic-assisted radical prostatectomy were evaluated retrospectively and 93 patients whose follow-ups were still ongoing were included in the study. Fifty-two patients received ART and 41 patients received SRT. External beam radiotherapy (EBRT) was applied to prostate bed (PB) with a median EBRT of 70 Gy (66-72 Gy) and/or pelvic lymphatics with 50 Gy. Biochemical relapse-free survival (bRFS) and treatment-related acute and late gastrointestinal (GI) and genitourinary (GU) toxicities were evaluated. The Mann-Whitney U and chi-square tests were used for univariate analysis to analyze clinicopathological variables associated with biochemical relapse-free and overall survival and to evaluate side effects. Logistic regression model was used for multivariate analysis to investigate the risk factors associated with toxicities.Results:The median age of the patients included in the study was 64 (50-82) years. The median follow-up period of the entire patient population was 30 months (range, 3-234 months). Adjuvant RT was applied to 52 patients with adverse pathological features such as postoperative surgical margin positivity, extracapsular extension and seminal vesicle involvement, while SRT was applied to 41 patients with a prostate-specific antigen level ≥0.2 ng/mL detected during follow-up and considered to have biochemical relapse. bRFS rates at 3 years were detected as 100% in the ART and 97.4% in the SRT arm. Acute and late side effects were evaluated according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer system, and acute and late GI and GU side effects were found to be similar in patients who underwent ART or SRT. In the multivariate logistic regression analysis in which the factors predicting the development of acute toxicity were investigated, the risk of developing acute toxicity was found to be higher in patients with lymph node involvement (p=0.047) and those who underwent whole pelvic RT (WPRT) compared to those who received RT applied only to PB (p= 0.002). When the patients who received WPRT using volumetric arc therapy (VMAT) were compared with those who had radiotherapy delivered only to PB, grade ≥2 acute GI side effects were detected in 4.2% and 1.4% of the patients, respectively (p=0.002). On the other hand, grade ≥2 acute GU side effects were found in 12.5% and 5.7% of the patients, respectively. When WPRT vs only PB was compared, any statistically significant difference was not found in terms of late toxicity.Conclusion:Postoperative radiotherapy improves biochemical relapse-free survival in patients with adverse prognostic factors. Despite low incidence of side effects, postoperative pelvic radiotherapy results in significant increases in the acute gastrointestinal toxicity rates. Advanced treatment techniques such as VMAT should be considered in pelvic radiotherapy so as to reduce the incidence of these side effects. It should be noted that in order to improve the quality of life of the patients, timely administration of early SRT showed comparable cancer control rates while reducing potential overtreatment toxicity.

Keywords

• adjuvant radiotherapy
• adverse prognostic factors
• prostate cancer
• salvage radiotherapy