X. Ren, S. Qin, M. Ma, X. Qi, Y. Bai, J. Chen, F. Lyu, H. Li, and X. Gao; Department of Radiation Oncology, Peking University First Hospital, Beijing, China
Purpose/Objective(s): After Radical prostatectomy (RP) for patients with localized prostate cancer (PC), an estimated 15-25% of men will develop a prostate specific antigen (PSA) recurrence. Postoperative radiotherapy (RT) is recommended for patients with PSA recurrence as salvage RT and patients with high-risk pathologic features as adjuvant RT. To date, the dose of postoperative RT is recommended as a minimum level of 64-65 Gy with conventional fractionation. Due to the low a/ß ratio of PC, hypofractionated RT has the potential to realize the dose escalation without increasing treatment duration and toxicity. However, current data on postoperative hypofractionated RT is largely based on small sample size retrospective studies. The aim of the present study is to evaluate the clinical outcome, acute and late toxicity of a large retrospective cohort, and we also identify the factors affecting late GU in this real world setting. Materials/
Methods: We conducted a retrospective analysis of all PC patients who received post-operative hypofractionated RT from 2017 to 2019 at our institution. The inclusion criteria were as follows: (1) RP and histologically confirmed PC; (2) the dose of prostatic bed CTV was 62.75 Gy in 25 fractions; (3) no distant metastases before RT. Daily image-guided intensity modulated RT was performed in all patients. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity were graded using CTCAE, version 5.0. Endpoints of the analysis were outcome in terms of overall survival (OS), disease specific survival (DSS), biochemical progression free survival (bPFS) and event free survival (EFS). These endpoints were analyzed with the Kaplan-Meier method. Univariate analysis of freedom from =G2 incontinence worsening (FFG2I) was performed with the log-rank test. Results: A total of 239 patients were included in the analysis. The median age was 65 years (range: 48-84) and median follow-up was 54 months (range: 13-76). At baseline, patients with =pT3a, positive margin, Gleason score 8-10 and PSAmax =20 ng/mL took 73.2%, 60.7%, 52.7% and 39.7%, respectively. The 4-year OS, DSS, bPFS and EFS rate were 97.1%, 99.2%, 87.1% and 80.6%, respectively. 7.1% and 2.5% patients reported acute G2 GI and G2 GU toxicity. We did not observe acute G3 GU or GI toxicity. 2.1%, 22.2% and 8.8% patients reported late G2 GI, G2 GU and G3 GU toxicity. Most common late =G2 GU events were incontinence worsening. The 4-year FFG2I was 69.9% among men with a bladder V50 Gy =19.2% (median) vs 83.3% in men with a V50 Gy <19.2% (p=0.019). The 4-year FFG2I was 51.5% among men with cystoscopy vs 80.6% in men without cystoscopy (p<0.001). Conclusion: The clinical control in this hypofractionated series appears promising, and longer follow-up may be needed to collect more late toxicity data, especially GU toxicity. Limiting bladder V50 Gy may reduce RT-related incontinence worsening. The benefit and risk should be balanced when performing cystoscopy.
.jpg "Xue-Ying Ren, MD photo")