The use of a hydrogel spacer to reduce safety risks in postoperative salvage radiotherapy for prostate cancer, "Beyond the Abstract," by Michael Pinkawa, MD

BERKELEY, CA ( - In recent years, technical advances in intensity-modulated radiotherapy (IMRT) and image-guided radiotherapy (IGRT) have led to improved dose conformity. Consequently it is possible to reduce safety margins around the CTV (clinical target volume), thus reducing toxicity risks associated with higher doses. Total doses of 60-64Gy have been used in prospective adjuvant post-prostatectomy radiotherapy studies in the past. Retrospective studies suggest a benefit of dose escalation, particularly for salvage radiotherapy. Minimum doses of 64-66Gy are recommended in the ASTRO (American Society for Radiation Oncology) / AUA (American Urological Association) guidelines for salvage radiotherapy.

A dose-escalated treatment concept for a patient with a macroscopic local recurrence many years after radical prostatectomy is presented in this report. The feasibility of applying a hydrogel spacer to protect the anterior rectal wall has been evaluated in this case.

A 77-year-old patient presented 20 years after radical prostatectomy with a digitally palpable local recurrence at the urethrovesical anastomosis (PSA 5.5ng/ml). A local recurrence with a maximum diameter of 2.5cm was diagnosed in 18F-choline-PET/CT and MRI. Local lymph node or distant metastases were not diagnosed in these imaging studies.

The hydrogel spacer (10ml, SpaceOAR™) was injected between the local recurrence and rectal wall under transrectal ultrasound guidance. Treatment planning was performed with an intensity-modulated technique up to a total dose of 76Gy in 2Gy fractions. The same planning was performed based on a computed tomography, before spacer injection, for comparison.

The local recurrence, initially directly at the rectal wall, could be displaced > 1cm from the rectal wall after hydrogel injection. With a mean total dose of 76Gy to the planning target volume, rectal wall volumes included in the 76Gy, 70Gy, 60Gy, 50Gy isodoses were 0cm3, 0cm3, 0cm3, and 0.4cm3 with a spacer and 1.5cm3, 2.9cm3, 4.5cm3, and 6.2cm3 without a spacer, respectively. The corresponding rectum (including filling) volumes within the 76Gy, 70Gy, 60Gy, 50Gy isodoses were 0cm3, 0cm3, 0cm3, and 0.4cm3 with a spacer and 2.7cm3, 7.2cm3, 12.4cm3, and 17.7cm3 without a spacer, respectively. The patient reported rectal urgency during radiotherapy, completely resolving after the end of treatment. A PSA measurement was performed one week before the end of treatment, indicating a PSA level of 5.4ng/ml – thus, no change in comparison to the baseline level of 5.5ng/ml before treatment. Two, 5, and 8 months after the end of radiotherapy, PSA level decreased considerably to 1.3ng/ml, 0.9ng/ml and 0.9ng/ml, respectively.

Hydrogel injection can be considered in specifically selected patients for postoperative salvage radiotherapy. The prerequisites for the applied strategy is the presence of a single, macroscopically visible tumour recurrence which is located in the vicinity of the rectal wall as well as a very high level of confidence that the lesion is the only site of recurrence.

Written by:
Michael Pinkawa, MD as part of Beyond the Abstract on 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, RWTH Aachen University, Pauwelsstrasse 30, 52057, Aachen, Germany

Application of a hydrogel spacer for postoperative salvage radiotherapy of prostate cancer - Abstract

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