The Use of Hyaluronic Acid (BarrigelR) in Rectal Spacing for Prostate Cancer Radiotherapy.

Abstract

Introduction: To report the feasibility, post-operative complications and recto-prostatic separation achieved with hyaluronic acid (HA) [BarrigelR] inserted into the perirectal fat before definitive prostate radiotherapy (RT). Patients and Methods: Fifty-five patients with clinical stage T1-3 prostate cancer underwent transrectal ultrasound guided transperineal insertion of fiducial markers and HA into the perirectal space before volumetric arc RT (VMAT) between 7/2020 and 2/2021. Post insertion CT and MRI scans were obtained for treatment planning. HA feasibility, safety and recto-prostatic separation was assessed. The prescribed dose to the planning target volume (PTV) ranged from 78-80 Gy in 39-40 fractions to 60-62 Gy in 20 fractions. Result(s): HA insertion was completed with a 100% success rate. This was rated as 'easy' to 'very easy' 100% of the time. There were no device related complications, rectal perforation, serious bleeding, infections or allergic reactions. The mean prostate size was 43 cc (15-100 cc). Recto-prostatic separation at the base (measured 5 mm below the prostate base), mid gland and apex (measured 5 mm above the prostate apex) were 13 mm (8-16 mm), 11.5 mm (8-15 mm) and 9.5 mm (6-12 mm) respectively. The HA was also symmetrically placed in breadth at the midgland in all patients. The mean rectal volume receiving 70 Gy (rV70) was 3% (0.1-9.7%) for patients receiving 78-80 Gy. The mean rectal volume receiving 53 Gy (rV53) was 4.1% (0.8-11.3%) for patients receiving 60-62 Gy. The length of follow up does not permit assessment of late toxicity. Conclusion(s): BarrigelR was successfully inserted in all patients and was very well tolerated. Recto-prostatic separation was symmetrical in length from the base to the apex and in breadth at the midgland. The mean rV70 and rV53 recorded in these patients were significantly reduced compared to nonspacer cohorts.