Application technique: placement of a prostate–rectum spacer in men undergoing prostate radiation therapy

Abstract

E 6 4 7What ' s known on the subject? and What does the study add? Different spacing agents have been tested to reduce incidential radiation exposure of the rectum during radiotherapy to the prostate. These agents all had certain drawbacks; either the created space was too small or the agents used did not stay in place during radiotherapy treatment.The study describes the transperineal injection technique of a spacing agent in detail. Furthermore it shows the safety and effi cacy of the spacing hydrogel used and shows that it overcomes some of the drawbacks of the previously examined spacing agents. OBJECTIVE• To describe the technique used to apply a hydrogel spacer between the prostate and rectum so as to decrease the radiation dose to the rectum in patients with prostate cancer who are undergoing radiotherapy. METHODS• A prospective study evaluating the safety and effi cacy of prostate -rectum spacer injection was conducted in 29 male patients with prostate cancer scheduled for radiotherapy.• Spacing hydrogel was injected into the perirectal space using a transperineal approach under real-time transrectal ultrasonography guidance.• With the needle tip positioned beyond the rectourethralis muscle, saline injection opened the space between Denonvilliers ' fascia and the anterior rectal wall, allowing needle advancement to the mid-prostate without rectal wall injury. Injection of hydrogel precursors further opened this space, which was then maintained as a result of hydrogel polymerization.• Procedure duration and adverse events were monitored. Computed tomography and/or magnetic resonance imaging simulation scans were performed before and after injection. The hydrogel-created space was measured and the reduction in percent volume of the rectum receiving at least 70 Gy (rectal V70) was determined. RESULTS• Hydrogel injection resulted in mean ( SD ) additional prostate -rectum space relative to baseline of 9.87 (5.92) mm.• The mean ( SD ) procedure time, as measured by needle insertion and removal, was 6.3 (3.2) min.• The relative reduction in rectal V70 was 60.6%.• There were no unanticipated adverse events associated with the hydrogel procedure or the hydrogel. CONCLUSIONS• Hydrogel spacer injection using hydrodissection is a fast and effective procedure to separate the rectal wall from the prostate in order to avoid rectal toxicity.• Hydrogel spacer injection resulted in the addition of ∼ 1 cm of space • Computed incidental radiation exposure, the rectal V70, was substantially reduced.

Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

“…It should be noted that whilst a number of clinical studies have reported hydrogel spacers to be safe [3,6], one published case report linked a rectal ulcer to a hydrogel insertion [28] and their use was halted in a recent trial, where two rectal fistulas were presumed due to the gradual accumulation of gel within the confines of the anterior rectal wall, as seen on magnetic resonance imaging during the course of the treatment [29]. However, the latter publication reported that in addition to gel migration, variations in individual patient radiosensitivity could have played a role, on-treatment image guidance was limited to orthogonal x-rays (it did not state whether alignment based on bony anatomy or prostate fiducials), and the in vivo dose to the anterior rectal wall was not known precisely [29].…”

“…Injected hydrogel spacers (SpaceOAR, Augmenix Inc.) typically result in a separation of approximately 1 cm between the rectum and prostate [3]. This separation remains stable over 10-12 weeks [4] enabling substantial rectal dose reductions in the 60-70 Gy region [5].…”

Validation of rectal sparing throughout the course of proton therapy treatment in prostate cancer patients treated with SpaceOAR®

“…All hydrogel and fiducial marker placement were performed during the same outpatient procedure under local perineum skin numbing, following general application technique guidelines previously published 20. Specifically, at our facility, all patients had a fleet enema 2–3 h prior to the procedure.…”

Internal Immobilization: From Rectal Balloon to Hyaluronic Acid

“…The mean rectal IMRT doses per fraction were reduced from 1.05 to 0.74 Gy with hyalform (Wilder et al 2011). Hatiboglu et al (2012) analyzed 27 patients receiving hydrogel injection with regard to space creation, stability of spacer, duration of procedure, and reduction of rectal dose for prostate cancer patients receiving IMRT up to 78 Gy. Before hydrogel insertion the mean space between prostate and rectum was about 5 mm compared to about 15 mm after insertion, resulting in a space creation of 10 mm.…”