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Semin intervent Radiol 2020; 37(03): 324-329
DOI: 10.1055/s-0040-1713449
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Protection of the Rectum during Prostate Radiation

Swar H. Shah
1   Department of Radiology, Rochester General Hospital, Rochester, New York, New York
,
Atul K. Gupta
1   Department of Radiology, Rochester General Hospital, Rochester, New York, New York
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Publication History

Publication Date:
31 July 2020 (online)

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Prostate cancer is the most common malignancy in men, with an estimated 191,900 new diagnoses and 33,330 deaths in 2019.[1] Treatment modalities range from radical prostatectomy to radiation therapy to close observation and are standardized by national guidelines.[2]

Radiation therapy for prostate cancer can take the form of placement of brachytherapy seeds into the prostate or external beam radiation therapy. Scatter radiation from these techniques, however, provides a significant risk to adjacent organs. As radiation therapy technology and administration techniques have improved, a significant limiting factor to dose administration is the risk of rectal toxicity from scatter radiation.[3] Depending on the dose delivered and sensitivity of the organ, in this case the rectum, there may be long-lasting radiation injury.

As radiation dose is reduced by the square of the distance, separating the prostate from the rectum is a very effective means of decreasing radiation exposure. The inverse holds true as well, as some studies have suggested dose modulation in patients with decreased prostate to rectum distances.[4] By definition, this makes the rectum an “organ at risk.”

Increasing the distance between the prostate and rectum serves as a protective mechanism for the rectum and may allow for increased and more effective dose to the prostate. Hydrodissection with saline to increase this space, while technically feasible, proves ineffective as saline quickly dissipates and is resorbed. However, placement of a hydrogel into the peri-rectal fat with ultrasound guidance can create up to 1.5 cm of separation between the prostate and rectum. This hydrogel remains in place for approximately 3 months. Use of rectal spacer material has been established to be safe and effective in limiting rectal toxicity.[5] [6] [7] Herein, we review the technique and considerations for placement of a hydrogel between the prostate and rectum in patients undergoing radiation therapy for prostate cancer.