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Background
The insertion of the SpaceOAR hydrogel is an optional procedure offered to patients during prostate radiotherapy in an attempt to reduce risk of rectal toxicity. Owing to the proximity of the rectum to the prostate, curative radiotherapy for prostate cancer inevitably results in irradiation of the anterior rectal wall. 1 2 The SpaceOAR System (Augmenix Inc, Waltham, Massachusetts, USA) is a synthetic polyethylene glycol hydrogel injected between the prostate and the rectum, thereby distancing the rectum away from the prostate, reducing irradiation of the anterior rectal wall. 3-8
The SpaceOAR is inserted trans-perineally under trans-rectal ultrasound (TRUS) guidance. When the precursor and the accelerator solutions that make up the SpaceOAR System are injected simultaneously into the perirectal space, the mixing of the two solutions initiates a cross-linking reaction that results in the formation of a soft polyethylene-glycol-based gel within seconds. After 12 weeks, the hydrogel hydrolyses and liquefies, and is absorbed. 9
To the best of our knowledge, this is the first report of rectal ulceration following SpaceOAR hydrogel insertion with low-dose-rate (LDR) prostate brachytherapy. In this case report, we discuss possible mechanisms of rectal injury and technical manoeuvres that may help to reduce risk of rectal ulceration during SpaceOAR hydrogel insertion.
Case presentation
A 66-year-old man was diagnosed with favourable intermediate risk prostate cancer. Baseline parameters included a prostate-specific antigen of 2.2 ng/mL and subtle non-specific firmness of the prostate gland bilaterally. On TRUS, the prostate had an estimated volume of 28 mL and prostate biopsies found evidence of multifocal Gleason score 3+4 adenocarcinoma. The patient was otherwise in good health although his history was relevant for a surgically resected atrial myxoma and coronary artery disease stenting. He also has a history of diverticulosis/diverticulitis and chronic renal impairment. Following consideration of management options, he elected to have treatment with LDR prostate brachytherapy.
Treatment
One month prior to LDR brachytherapy implant, a routine volume planning study was performed and three gold non-radioactive fiducial markers were inserted into the prostate. At the subsequent LDR brachytherapy implant, a total of 83 radioactive iodine-125 seeds were placed under TRUS guidance. The total prescribed dose was 145 Gy.
At the completion of the implant, SpaceOAR prosthesis was injected into the space between the prostate and the anterior rectal...