High-dose-rate fractionated brachytherapy monotherapy for localized prostate cancer: a systematic review and meta-analysis

Introduction
High-dose-rate (HDR) brachytherapy as primary therapy (monotherapy) is a standard National Comprehensive Cancer Network (NCCN) endorsed treatment option for patients with localized prostate cancer. Thus far, most data are limited to single-institution experiences. Accordingly, we sought to systematically review rates of biochemical recurrence-free survival (bRFS) and toxicity associated with fractionated HDR monotherapy.

Material and methods
A systematic review was performed using PubMed and Embase databases for relevant articles published between January 1999 and December 2019, according to preferred reporting items for systematic review and meta-analyses (PRISMA) guidelines. Included studies were limited to fractionated HDR monotherapy publications in full manuscript form with at least 5-year median follow-up, at least 80 patients included, and adequate reporting of bRFS and toxicity data. Meta-analyses were performed with random-effect modeling. Extent of heterogeneity between studies was determined using I2 and Cochran’s Q tests.

Results
Seven unique studies were identified, including 2,123 patients. NCCN low-, intermediate-, and high-risk patients comprised 40%, 40%, and 20% of patients, respectively. Median follow-up at the study group level was 74 months (range, 60-131 months). The 5-year bRFS rate was 95% (95% confidence interval [CI]: 93-96%), and after adjusting to control for publication bias, it was 96% (95% CI: 94-99%). Estimated adjusted late grade ≥ 3 genitourinary and gastrointestinal toxicity rates were 2% (95% CI: 1-4%) and 0.3% (95% CI: 0-1.1%), respectively.

Conclusions
Fractionated HDR monotherapy is associated with high rates of disease control and low rates of toxicity. Future studies are needed to better define the value of this treatment modality relative to other options.