Prostate motion during radiotherapy of prostate cancer patients with and without application of a hydrogel spacer: a comparative study

Radiat Oncol. 2015 Oct 24;10:215. doi: 10.1186/s13014-015-0526-1.


Background and purpose: The use of a tissue expander (hydrogel) for sparing of the rectum from increased irradiation during prostate radiotherapy is becoming popular. The goal of this study is to investigate the effect of a tissue expander (hydrogel) on the intrafraction prostate motion during radiotherapy.

Methods and material: Real time prostate motion was analysed for 26 patients and 742 fractions; 12 patients with and 14 patients without hydrogel (SpaceOAR™). The intra-fraction motion was quantified and compared between the two groups.

Results: The average (±standard deviation) of the mean motion during the treatment for patients with and without hydrogel was 1.5 (±0.8 mm) and 1.1 (±0.9 mm) respectively (p < 0.05). The average time of motion >3 mm for patients with and without hydrogel was 7.7 % (±1.1 %) and 4.5 % (±0.9 %) respectively (p > 0.05). The hydrogel age, fraction number and treatment time were found to have no effect (R (2) < 0.05) on the prostate motion.

Conclusions: Differences in intrafraction motion in patients with hydrogel and without hydrogel were within measurement uncertainty (<1 mm). This result confirms that the addition of a spacer does not negate the need for intrafraction motion management if clinically indicated.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Hydrogel, Polyethylene Glycol Dimethacrylate
  • Male
  • Motion
  • Prostatic Neoplasms / radiotherapy*
  • Radiographic Image Interpretation, Computer-Assisted / methods*
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Radiotherapy, Intensity-Modulated / methods
  • Tissue Expansion Devices*


  • Hydrogel, Polyethylene Glycol Dimethacrylate