Salvage brachytherapy for locally recurrent prostate cancer after external beam radiotherapy

External beam radiotherapy (EBRT) is a standard treatment for prostate cancer. Despite the development of novel radiotherapy techniques such as intensity-modulated conformal radiotherapy, the risk of local recurrence after EBRT has not been obviated. Various local treatment options (including salvage prostatectomy, brachytherapy, cryotherapy, and high-intensity focused ultrasound [HIFU]) have been employed in cases of local recurrence after primary EBRT. Brachytherapy is the first-line treatment for low-risk and selected intermediate-risk prostate tumors. However, few studies have examined the use of brachytherapy to treat post-EBRT recurrent prostate cancer. The purpose of this paper is to analyze the current state of our knowledge about the effects of salvage brachytherapy in patients who develop locally recurrent prostate cancer after primary EBRT. This article also introduces our novel permanent brachytherapy salvage method.There are various treatment options for patients who develop locally recurrent prostate cancer after primary EBRT. Agarwal et al. reported that androgen-deprivation therapy (ADT) was the most common salvage treatment (93.5%) for post-EBRT recurrent prostate cancer and that salvage brachytherapy was only performed in 0.2% of cases.1 The benefits of ADT are well-known; however, it is also associated with various adverse effects including a loss of libido, impotence, anemia, an increased incidence of skeletal fractures, and a higher cardiovascular mortality rate. Various local salvage treatment options including brachytherapy, radical prostatectomy, cryotherapy, and HIFU have been used to treat post-EBRT locally recurrent prostate cancer. Whole-gland salvage brachytherapy has demonstrated acceptable oncological outcomes; however, it can have significant side effects including incontinence, genitourinary toxicities, and gastrointestinal toxicities.2,3 Recently, focal salvage brachytherapy has been used to treat post-EBRT locally recurrent prostate cancer in order to reduce the frequency of adverse events while maintaining appropriate cancer control rates.4,5 However, only a few reports about focal salvage brachytherapy for post-EBRT locally recurrent prostate cancer have been published. In this article, we analyze the use of whole-gland and focal brachytherapy for post-EBRT locally recurrent prostate cancer, focusing on their clinical outcomes and toxicity. Recently, we started performing focal salvage brachytherapy based on three-dimensional cancer mapping data obtained using magnetic resonance imaging (MRI)-transrectal ultrasound (TRUS) fusion biopsy examinations. Herein, we introduce our novel permanent brachytherapy salvage method.