title: Application of a hydrogel spacer for postoperative salvage radiotherapy of prostate cancer.
abstract: BACKGROUND
  In contrast to primary radiotherapy, no reports are available for a hydrogel spacer application in postoperative salvage radiotherapy for prostate cancer.
  
  
  METHODS
  A 77-year-old patient presented 20 years after radical prostatectomy with a digitally palpable local recurrence at the urethrovesical anastomosis (PSA 5.5 ng/ml). The hydrogel spacer (10 ml, 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 76 Gy in 2-Gy fractions. The same planning was performed based on computed tomography before spacer injection for comparison.
  
  
  RESULTS
  The local recurrence, initially directly on the rectal wall, could be displaced more than  1 cm from the rectal wall after hydrogel injection. With a mean total dose of 76 Gy to the planning target volume, rectal wall volumes included in the 70 Gy, 60 Gy, 50 Gy isodoses were 0 cm(3), 0 cm(3), and 0.4 cm(3) with a spacer and 2.9 cm(3), 4.5 cm(3), and 6.2 cm(3) without a spacer, respectively. The patient reported rectal urgency during radiotherapy, completely resolving after the end of treatment. The PSA level was 5.4 ng/ml a week before the end of radiotherapy and dropped to 0.9 ng/ml 5 months after radiotherapy.
  
  
  CONCLUSIONS
  A hydrogel spacer was successfully applied for dose-escalated radiotherapy in a patient with macroscopic local prostate cancer recurrence at the urethrovesical anastomosis to decrease the dose at the rectal wall. This option can be considered in specifically selected patients.
authors.affiliation: Department of Radiation Oncology, RWTH Aachen University, Pauwelsstrasse 30, 52057, Aachen, Germany, MPinkawa@ukaachen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Pinkawa
authors.forename: Carolin
authors.initials: C
authors.lastname: Schubert
authors.forename: Nuria
authors.initials: N
authors.lastname: Escobar-Corral
authors.forename: Richard
authors.initials: R
authors.lastname: Holy
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Eble
mesh_terms: D000368:Aged; D019583:Dose Fractionation, Radiation; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D008422:Materials Testing; D018365:Neoplasm, Residual; D011182:Postoperative Care / Q000295:instrumentation / Q000379:methods; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D019736:Prostheses and Implants; D011835:Radiation Protection / Q000295:instrumentation*; D018714:Radiotherapy, Adjuvant / Q000295:instrumentation / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D016879:Salvage Therapy / Q000295:instrumentation*; D016896:Treatment Outcome
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate