Focal versus whole gland salvage brachytherapy for recurrent prostate cancer in the prostate specific membrane antigen PET era: a narrative review

Background and Objective: Prostate cancer is the second most common cause of cancer in men worldwide. A significant proportion of patients will develop biochemical failure after definitive radiotherapy and an increasing number of local failures are now identifiable with prostate specific membrane antigen (PSMA) positron emission tomography and computerized tomography (PET/CT). Brachytherapy (BT) represents an excellent option for definitive local salvage treatment. Consensus guidelines for the delivery of salvage BT are heterogenous and limited. Herein, we report the results from a narrative review analyzing whole gland and partial gland BT salvage to help guide treatment recommendations. Methods: The PubMed and MEDLINE databases were searched in October 2022 to identify studies analyzing BT salvage in patients with recurrent prostate cancer after definitive external beam radiation therapy (EBRT). 503 initial studies met search criteria. After title and abstract screening, 25 studies met inclusion criteria and full-text review was performed. Twenty studies were included for analysis. Reports included whole gland (n=13) and partial gland or focal (n=7) salvage BT. Key Content and Findings: The median 5-year biochemical failure free survival (BFFS) for men receiving whole gland BT salvage was 52%, which is comparable to 5-year recurrence-free survival (RFS) rates for other salvage treatment modalities (radical prostatectomy (RP) 54%, high-intensity focused ultrasound (HIFU) 53%, cryotherapy 50%). However, the median rate of severe genitourinary (GU) toxicity was lower (12%) compared to published rates for other treatment modalities (RP 21%, HIFU 23%, and cryotherapy 15%). Furthermore, patients receiving partial gland salvage BT had even lower median rates of grade 3 or higher GU toxicity (4% vs. 12%) and gastrointestinal (GI) toxicity (0% vs. 3%), with 3-year BFFS of 58%. Only two studies directly comparing BT whole versus partial gland salvage were identified with comprehensive literature search and neither provided specific comparison regarding prescription dose or dose constraints. Conclusions: This narrative review identified only two studies that directly compared whole versus partial gland BT salvage treatment. Neither report provided a specific comparison of recommendations for dosimetric technique or normal structure dose constraints. Therefore, this review highlights a significant gap in the existing literature and provides an important framework to guide radiation treatment (RT) recommendations for both whole gland and partial gland salvage BT in patients with recurrent prostate cancer.