External Beam Radiation Therapy (EBRT) is a key first-line treatment for high-risk prostate cancer, and is almost always combined with long-term androgen deprivation therapy (ADT)—typically for 18 to 36 months—to maximize effectiveness. EBRT uses high-energy beams to target the prostate and surrounding tissues, including the seminal vesicles and sometimes the pelvic lymph nodes, given the increased risk of microscopic spread.

This approach offers excellent cancer control, especially when combined with ADT, and is often chosen for patients who wish to avoid surgery or are not good surgical candidates. Side effects may include urinary frequency, bowel changes, and erectile dysfunction, but these are usually gradual and manageable. EBRT is supported by strong clinical evidence and major guidelines for high-risk disease.