Brachytherapy can be used in high-risk prostate cancer, but not as monotherapy—it is typically part of a combined treatment approach with external beam radiation therapy (EBRT) and long-term androgen deprivation therapy (ADT). This strategy, known as trimodal therapy, is used to intensify local treatment in patients with aggressive disease.

In this setting, brachytherapy boosts the total radiation dose delivered to the prostate, improving cancer control compared to EBRT alone. It is most suitable for patients with good urinary function, smaller prostate size, and who can tolerate a more aggressive regimen. However, due to higher toxicity risks—particularly urinary side effects—it requires careful patient selection and experienced providers.