Single-fraction high-dose-rate brachytherapy: a scoping review on outcomes and toxicities for all disease sites

Purpose
Brachytherapy is well positioned to safely deliver highly conformal single-fraction doses of radiation, which can lower costs and improve efficiency. Traditionally, high-dose-rate brachytherapy (HDR-BT) has been delivered over multiple treatments. A scoping literature review was conducted to better understand the available literature on single-fraction HDR-BT for all disease sites.

Material and methods
According to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, PubMed database was queried from 1994-2021 using the following search terms: ‘brachytherapy’, ‘high-dose-rate’, and ‘single-fraction’. A total of 53 studies met our exclusion criteria.

Results
Liver had the highest number of studies, with a total of 618 patients treated with doses ranging from 8 to 25 Gy. Median follow-up ranged from 11-33 months. Local control (LC) rates ranged from 37% to 98%. G3 acute/late toxicities or higher were reported in 3 patients. Prostate cancer included a total of 1,474 patients treated with doses ranging from 19 to 21 Gy. Median follow-up ranged from 20 to 72 months. Prostate specific antigen (PSA) control outcomes after definitive treatment ranged from 65% to 94%, and salvage treatments from 5% to 84%. G3 acute/late toxicities or higher ranged from 0 to 6%. Breast cancer included a total of 268 patients treated with doses ranging from 16 to 20 Gy. Median follow-up ranged from 24 to 72 months. LC rates were 100%. G3 acute toxicities or higher ranged from 0 to 6%. Regarding other cancers, conclusions were limited given the small number of patients within each respective site.

Conclusions
Currently used regimens appear safe, but efficacy vary by different disease sites. Outcomes are more promising for breast and liver, while are less encouraging for prostate. Additional prospective evaluation of single-fraction HDR-BT regimens are warranted.