Stereotactic body radiotherapy (SBRT) versus high dose rate (HDR) brachytherapy (BT) boost for high-risk (HR) prostate cancer.

Abstract

12 Background: Declining use of BT has prompted questions regarding the use of SBRT in HR patients. A systematic literature review was conducted to assess toxicity, and biochemical outcomes following SBRT or HDR BT boost in HR patients. Methods: A search was carried out on the PubMed and Embase databases, for studies published between 2007 and 2017, including HR patients treated with SBRT or HDR boost. Results: We identified 11250 articles, with 6 SBRT and 41 HDR boost studies eligible. The median follow-up was 3.5-5.5 and 2.6-10.3 years in SBRT and HDR boost studies, respectively. The five-year bDFS was 41%–96% in HDR and 69%–98% in SBRT boost studies. Toxicity was reported using the Radiation Therapy Oncology Group (RTOG) scale or the Common Terminology Criteria for Adverse Events (CTCAE) scale and/or validated patient reported Quality of Life (QoL) outcomes. Single SBRT and HDR studies reported 1 year IPSS scores < 7, with 2 SBRT reports of excellent outcomes by the EPIC scale. Acute grade 2 (G2) genitourinary (GU) toxicity ranged from 24-46% and 0.4-33% in SBRT and HDR boost studies, respectively. Late G2 GU toxicity occurred in 2.3-25% and 0-22% following SBRT and the HDR boost, respectively. Late grade 3 (G3) GU toxicity was reported in 0-2.3% and 0-10% with SBRT and HDR boost, respectively. Late G3 GU was reported in 0.8% (2/226) and 4% (114/2763) following SBRT and HDR boost, respectively. Acute G2 gastrointestinal (GI) was noted in 8-19% and 0-19% of SBRT and HDR boost studies, respectively. Late G3 GI was reported in 0-10% and 0-4.6% of SBRT and HDR boost studies, respectively. Late G3 GI was reported in 2% (5/226) and 0.6% (18/2829) of SBRT and HDR boost studies, respectively. Conclusions: SBRT boost may be associated with higher acute G2 but lower late G3 GU toxicity but was not shown by QoL reports, and could be due to selection bias, learning curves or other factors. Randomized trials and validated QoL instruments are needed to accurately compare SBRT to HDR boost.