Learning curve in the application of a hydrogel spacer to protect the rectal wall during radiotherapy of localized prostate cancer

Urology. 2013 Oct;82(4):963-8. doi: 10.1016/j.urology.2013.07.014.


Objective: To evaluate the effect of increasing experience on hydrogel dimensions, rectal dose, and acute toxicity, and to discuss important technical issues gained from this experience.

Methods: Sixty-four consecutive patients with prostate cancer were included in this analysis (G1/G2 corresponding to first/second 32 patients) after injection of 10 mL spacer gel. All patients were treated with a 5-field intensity-modulated radiotherapy technique to 76-78 Gy. Treatment toxicity was evaluated with a validated quality of life questionnaire (expanded prostate cancer index composite) before and after radiotherapy.

Results: Rectum volume could be entirely excluded from the planning target volume in 31% in G1 vs 56% in G2 (P = .04). Increasing symmetry was detected comparing the first 15 patients to the subsequent rest, with mean differences between right and left of 0.6 cm vs 0.3 cm at the midgland (P = .03). Mean distance between prostate and anterior rectal wall increased from 0.8 cm/1.1 cm/0.8 cm (G1) at the base/middle/apex to 1.3 cm/1.5 cm/1.2 cm (G2), respectively, so that the dose to the rectum decreased significantly (6% vs 2% of the volume inside the 70 Gy isodose; P <.01). Bowel function and bother score changes were smaller comparing baseline with last day of radiotherapy levels (mean 16/18 in G1 vs 9/12 in G2).

Conclusion: A learning curve could be demonstrated in our patient population, respecting improved and more symmetrical spacer placement, improved treatment planning, and less treatment-related acute toxicity. Several important technical aspects need to be considered.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Hydrogel, Polyethylene Glycol Dimethacrylate / administration & dosage*
  • Learning Curve*
  • Male
  • Prostatic Neoplasms / radiotherapy*
  • Radiation Injuries / prevention & control*
  • Radiation Oncology / education
  • Rectum*


  • Hydrogel, Polyethylene Glycol Dimethacrylate