Abstract
PURPOSE: To correlate changes in urinary patient-reported outcomes including the International Prostate Symptom Score (IPSS), acute urinary retention and urethral stricture with urethral dose in those treated with low dose rate (LDR) prostate brachytherapy. MATERIALS AND METHODS: Patients treated with prostate LDR between 2012 and 2019 (n=117) completed IPSS urinary symptom assessments prior to treatment and at each follow-up. CT simulation was obtained with urinary catheter 1-month post-implant for dosimetric analysis. 113 patients with pre- and ≥1 post-LDR IPSS score available were analyzed. Urethral dosimetric parameters including U75, U100, U125, U150 and U200 were abstracted from post-implant dosimetry and assessed for association with urinary toxicity using bivariate logistic regression and Spearman correlation. Outcomes included clinically significant change (CSC, defined as 4 or more points or 25% rise above baseline) in IPSS score at 6 and 12 months, acute urinary retention (AUR), and urethral stricture (US). RESULTS: 89 (79%) patients were treated with LDR monotherapy (145 Gy) and 24 (21%) with LDR boost (110 Gy) with external beam radiation therapy. Twenty (18%) had baseline IPSS ≥15. Median IPSS scores were: baseline 6 (3-12; n=113), 1-month 17 (10-25; n=110), 6 months 12 (7-18; n=77), 1 year 8 (5-14; n=52). CSC-6 was observed in 59 (77%), CSC-12 in 26 (50%), AUR in 12 (11%), and US in 4 (4%). No association was identified between urethral dose parameters and CSC-6, CSC-12, AUR, or US. No correlation between urethral dose and IPSS at 6- and 12-months was identified. The IPSS ≥15 group exhibited lower rates of CSC-12 (13% v. 57%, p=0.05) but not CSC-6 (55% v. 80%, p=0.12). CONCLUSIONS: We did not find a relationship between urethral dose and IPSS elevation, AUR or US. We did identify a significantly lower change in IPSS at 12 months for those with baseline IPSS ≥15 compared to those with low baseline scores.