Nonmetastatic castration‐resistant prostate cancer treated with salvage focal brachytherapy after external beam radiotherapy

INTRODUCTION: The efficacy of salvage local therapy after external beam radiotherapy has recently gained attention. However, a challenge with these therapies is the risk of significant genitourinary and gastrointestinal toxicity. Focal brachytherapy may be a treatment option because of its potential to reduce side effects. CASE PRESENTATION: A patient with castration‐resistant prostate cancer was found to be free of metastases on whole‐body magnetic resonance imaging following external beam radiotherapy, and prostate biopsy revealed a localized recurrence in the ventral prostate. The patient underwent salvage focal brachytherapy and had a prostate‐specific antigen progression‐free survival of 23 months. No adverse effects were observed following salvage brachytherapy. CONCLUSION: Our case suggests that salvage focal brachytherapy may be an effective local treatment option for nonmetastatic castration‐resistant prostate cancer that has relapsed after external beam radiotherapy, wherein the lesion is confined to a small area within the prostate.