Hydrogel Spacer Rectal Wall Infiltration Associated With Severe Rectal Injury and Related Complications After Dose Intensified Prostate Cancer Stereotactic Ablative Radiation Therapy

Abstract

The risk of rectal toxicity during and after prostate cancer radiation therapy is common to all treatment regimens. Hydrogel rectal spacers are increasingly being used to mitigate this risk and to facilitate dose-escalation, but also may infiltrate the rectal wall, with unclear clinical implication. We present a case of significant infiltration associated with severe late rectal injury (grade 4) and further grade 3 to 4 sequelae (recto-urethral fistula and associated osteomyelitis requiring exenteration) after high-dose stereotactic body radiation therapy for localized prostate cancer. The injury's temporal pattern associated with the expected timing of gel dissolution and displacement of infiltrated rectal layers potentially toward high dose regions together suggest a contributing role of the infiltration to the injury. In light of the rapid increase of hydrogel rectal spacer utilization, we review the case's evolution, concerning imaging findings, and associated literature and make suggestions regarding treatment planning and endoscopic assessment in the setting of infiltration or expected injury.

Dose-Intensified Stereotactic Ablative Radiation for Localized Prostate Cancer

“…This trend of higher incidence of late grade II GU toxicity seen with higher doses provides some clarity for the high late grade II GU toxicity in this experience with 45 Gy in 5 fractions, along with reassurance for the gradual resolution of symptoms in the longer follow-up period. Late grade ≥ III GU toxicity in our cohort was 2.1%, which is consistent with 2.2% reported by Catton et al Of note, toxicity data collection in this study ended in January 2020, and one patient with grade III GU toxicity ended up developing grade IV GU toxicity in March 2020, which was published as a case report ( 25 ). Given our short toxicity follow-up, toxicity is probably underreported.…”

“…Pathology reports showed adenocarcinoma with marked radiation-induced changes at the urethra margin without extraprostatic disease or seminal vesicle invasion. This case was notable for marked rectal wall infiltration of hydrogel spacer; given the timeline of the symptom onset correlating to expected resolution time of spacer gel, there may have been an interaction between RT injury and spacer gel infiltration that is not fully understood, as described in more detail in the published case report for this event ( 25 ).…”

Case Report: Reversal of Hyaluronic Acid Rectal Wall Infiltration with Hyaluronidase

“…Some degree of rectal wall infiltration was found to occur in 6% of cases in the randomized hydrogel spacer trial ( 3 ), none of which required further intervention. However, the potential consequences of more severe gross rectal wall infiltration may include ischemia of the rectal mucosa leading to severe pain and ulceration, which can then lead to superinfection and pelvic abscess formation, and subsequently recto-prostatic fistulas requiring major surgical intervention such as a defunctioning ileostomy/colostomy or even pelvic exenteration ( 9 , 10 ). Notably, McLaughlin et al.…”

Rationale for Utilization of Hydrogel Rectal Spacers in Dose Escalated SBRT for the Treatment of Unfavorable Risk Prostate Cancer

“…Accurate placement is critical to maximize the benefits afforded by the hydrogel rectal spacer, and this is especially true when employing dose escalated regimens ( 51 ). Typically placement is performed at the same time as fiducial marker placement (or brachytherapy), adding minimal procedural time ( 52 ).…”

“…Nonetheless, RWI should be treated with a high degree of caution given the possibility of catastrophic toxicity if it is not identified prior to definitive treatment. In one case report of a patient undergoing dose-escalated SBRT (45 Gy in 5 fractions) with a rectal spacer, RWI was not identified during treatment planning, and the patient ultimately required abdomino-perineal resection (APR), cystoprostatectomy, and ileal conduit placement secondary to complications from a large recto-urethral fistula ( 51 ). In retrospect, hydrogel was identified within the submucosa of the rectum, secondary to delamination and discontinuity of the muscularis propria.…”