Treatment of low-risk prostate cancer: a retrospective study with 477 patients comparing external beam radiotherapy and I-125 seeds brachytherapy in terms of biochemical control and late side effects.

Purpose: The goal of our study was comparison of external beam radiotherapy (EBRT) and I‑125 seeds brachytherapy in terms of biochemical control and development of late gastrointestinal and genitourinary side effects.
Patients and Methods: 477 low-risk prostate cancer patients treated between 2000 and 2019 at our department using either I‑125 seeds brachytherapy or EBRT with a dose of 74 or 78 Gy were reviewed for our analysis. 213 patients were treated with EBRT and 264 with seeds.
Results: Patients were followed up yearly with a median follow-up of 70 (3-192) months. The biochemical no evidence of disease (bNED) rates after 5 years were 95% for both EBRT and seeds, and after 10 years 87% for EBRT and 94% for seeds using the Phoenix criteria, although no significant difference was observed. Concerning gastrointestinal side effects, EBRT showed significantly higher rates of RTOG grade ≥2 toxicity compared to seeds, but at no point in follow-up more than 15% of all patients. On the other hand, genitourinary side effects were significantly more prevalent in patients treated with seeds, with 40% RTOG grade ≥2 toxicity 12 months after treatment. Nevertheless, both types of side effects decreased over time.
Conclusion: Both EBRT and seeds provide excellent biochemical control with bNED rates after 10 years of about 90%. In terms of side effects, patients treated with seeds show higher grades of genitourinary side effects, while patients treated with EBRT show higher grades of gastrointestinal side effects.