We conducted a multicentre feasibility study to assess the ability to randomise patients between image-guided radiotherapy (IGRT) and IGRT + high dose rate (HDR) brachytherapy boost and to adhere to appropriate radiation quality assurance standards.

The primary end point was to determine the ability to randomise 60 patients over an 18 month period. Arm 1 (IGRT) patients received 78 Gy in 39 fractions or 60 Gy in 20 fractions (physician's preference), whereas arm 2 (IGRT + HDR) received 37.5 Gy in 15 fractions with HDR boost of 15 Gy. The secondary end points included >grade 3 acute genitourinary and gastrointestinal toxicity, using Common Terminology Criteria for Adverse Events version 4.0 at 3 months, validation of a prospectively defined radiation oncology quality assurance to assess treatment compliance. All analyses were descriptive; no formal comparisons between treatment arms were carried out.

Between April 2014 and September 2015, 57 National Comprehensive Cancer Network (NCCN)-defined intermediate-risk prostate cancer patients were randomised between IGRT alone (arm 1; n = 29) and IGRT plus HDR brachytherapy boost (arm 2; n = 28). Overall, 93% received the treatment as randomised. There were four patients (one on IGRT arm 1 and three patients on the IGRT + HDR arm 2) who were treated differently from randomisation assignment. For the 29 patients receiving IGRT (arm 1), there were 14 cases reported with minor deviations and three with major deviations. For patients on IGRT + HDR (arm 2), there were 18 cases reported with minor deviations and two with major deviations. At 3 months in the IGRT group (arm 1), one patient reported grade 3 diarrhoea, whereas in the IGRT + HDR group (arm 2), two patients reported grade 3 haematuria. No other gastrointestinal and genitourinary toxicities were reported.

The pilot study showed the feasibility of randomisation between treatment with IGRT alone versus IGRT + HDR boost. Treatment compliance was good, including adherence to quality assurance standards.