Use of Rectal Balloon Spacer in Patients with Localized Prostate Cancer Receiving External Beam Radiotherapy

•The use of the balloon rectal spacer improves rectal dosimetry resulted in a median relative rectal dose reduction of 91.8%.•The median separation between the prostate and rectum achieved 1.6 cm post-implant, consistent with the reproducibility and pre-formed volume of the balloon.•The balloon spacer was well-tolerated, with only mild procedural adverse events and low rates of acute and late gastrointestinal and genitourinary toxicities.•The balloon spacer insertion technique keeps the needle away from the rectal wall. It includes the use of a blunt-dissection tip which reduces the risk of rectal injuries.•The balloon spacer is well visualized on all imaging modalities, including TRUS, CT and MRI which facilitates accurate placement and monitoring of the spacer during radiation therapy.