BERKELEY, CA (UroToday.com) - Definitive radiotherapy is a well-recognized treatment option for localized prostate cancer. Many technical advances have been implemented in the clinical routine in the last decade, allowing a safer dose escalation to the prostate. Intensity-modulated radiotherapy improves dose conformity. Image-guided radiotherapy is used to visualize the prostate before or during (real-time tracking) treatment, allowing a reduction of safety margins and treatment volume.
Rectum toxicity is a dose-limiting toxicity. Dose-volume correlations have been reported in many studies. Grade 2 or higher late gastrointestinal toxicity has been often reported in the range of 20-30%. Lower volumes within high isodose levels are associated with lower toxicity rates.
The application of a spacer to increase the distance between the prostate and anterior rectal wall is an innovative technique, considerably reducing the dose to the rectum. Requirements for an ideal spacer are a quick and well-tolerated procedure under local aneasthesia as well as stability during several weeks of radiotherapy treatment. An optimal spacer should be biodegradable and not toxic or allergenic. Hyaluronic acid, human collagen, an inflatable balloon, or hydrogel are potential materials to create the desired effect. The number of clinical studies is rapidly increasing.
The spacer is usually injected or implanted using a transrectal ultrasound after prior hydrodissection to clearly create and visualize a space between the rectal fascia and Denonvilliers’ fascia. Well-tolerated injection or implantation techniques and low rectal treatment-related toxicity have been demonstrated in prospective studies.
To achieve the optimum advantage, specific criteria must be applied for radiotherapy treatment planning, including spacer volume in rectum volume. All spacer applications have shown significant dose reductions to the rectum. With a resulting distance of about 1cm between the prostate and rectal wall, rectum volume can be excluded from the planning treatment volume and the 95% isodose.
Long-term clinical results and the results of randomized studies are needed to better define the beneficial effect for the patient. The greatest benefit can be expected for patients with specific risk factors for increased rectal toxicity, hypofractionated concepts, or re-irradiation.
Written by:
Michael Pinkawa, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Radiation Oncology, Rheinisch-Westfaelische Technische Hochschule Aachen University, Pauwelsstrasse 30, 52057 Aachen, Germany
Spacer application for prostate cancer radiation therapy - Abstract
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