Hydrogel spacer distribution within the perirectal space in patients undergoing radiotherapy for prostate cancer: Impact of spacer symmetry on rectal dose reduction and the clinical consequences of hydrogel infiltration into the rectal wall

Publication date: Available online 17 October 2016
Source:Practical Radiation Oncology
Author(s): Benjamin W. Fischer-Valuck, Anupama Chundury, Hiram Gay, Walter Bosch, Jeff Michalski
PurposeHydrogel prostate-rectum spacers, biomaterials placed between the prostate and rectum, continue to gain interest as a method to reduce or limit rectal dose during dose escalated prostate cancer radiation therapy. Since the spacer is initially injected into the perirectal space as a liquid, the final distribution can vary. The purpose of this study was to evaluate hydrogel spacer (SpaceOAR® system) implantation and distribution from a recent prospective randomized control trial and correlate spacer symmetry with rectal dose reduction as well as rectal wall infiltration (RWI) to acute and late toxicity.Methods and MaterialsT2-weighted magnetic resonance imaging images for 149 patients enrolled on a prospective clinical trial who received transperineal spacer injection were assessed for hydrogel spacer midline symmetry and RWI using a semi-qualitative scoring system. Symmetry was then correlated to rectal dose reduction using a student t-test (one tailed, paired) while a Fisher's Exact test was used to correlate RWI with acute and late rectal toxicity. All patients had control treatment plans created prior to spacer injection.ResultsHydrogel spacer was symmetrically placed at midline for 71 (47.7%) patients at the prostate mid-gland as well as one centimeter superior and inferior to mid-gland. The remaining 78 (50.9%) patients had some level of asymmetry with only 2 (1.3%) having far lateral-distribution (i.e>2cm) of hydrogel spacer. As the hydrogel spacer became more asymmetric, the level of rectal dose reduction relative to their control plans decreased. However, all but the most asymmetrical 1.3% had significant rectal dose reduction (p<0.05). Rectal wall hydrogel spacer infiltration was seen in 9 (6.0%) patients. There was no correlation between RWI and procedure-related adverse events or acute/late rectal toxicity.ConclusionsSignificant reduction of rectal dose can still be achieved even in the setting of asymmetric hydrogel spacer placement. RWI does not correlate with patient complications.



from Cancer via ola Kala on Inoreader http://ift.tt/2eHu6qY
via IFTTT