Use of rectal balloon spacer in patients with localized prostate cancer receiving external beam radiotherapy

Objective: To evaluate the efficacy of the balloon spacer when used to reduce the radiation dose delivered to the rectum in prostate cancer patients undergoing external beam radiotherapy. Method: A single center retrospective analysis including 75 PC patients with localized T1-T3a disease who received balloon spacer followed by EBRT. Pre- and post-implantation computed tomography (CT) scans were utilized for treatment planning for standard EBRT (78-81 Gy in 1.8-2 Gy fractions). Rectal dosimetry was assessed using DVHs, and toxicities were graded with CTCAE v.4. Results: A median (IQR) prostate-rectum separation resulted in 1.6 cm (1.4-2.0) post balloon spacer implantation. Overall, 90.6 % (68/75) of patients had a clinically significant 25 % relative reduction in the rectal with a median relative reduction of 91.8 % (71.2-98.6 %) at rV70. Three (4.0 %) patients reported mild procedural adverse events, anal discomfort and dysuria. Within 90 days post-implantation, five patients (6.67 %) and 1 patient (1.33 %) reported grade 1 and grade 2 rectal toxicities (anal pain, constipation, diarrhea and hemorrhoids). Genitourinary (GU) grade 1 toxicity was reported in 37 patients (49.33 %), with only one patient (1.33 %) experiencing grade 2 GU toxicity. No grade ≥ 3 toxicity was reported. Conclusion: Balloon spacer implantation effectively increased prostate-rectum separation and associated with dosimetric gains EBRT for PC stage T1-T3a. Further controlled studies are required to ascertain whether this spacer allows for radiotherapy dose escalation and minimizes gastrointestinal (GI) toxicity.