Prediction of rectum and bladder morbidity following radiotherapy of prostate cancer based on motion-inclusive dose distributions

Radiother Oncol. 2013 May;107(2):147-52. doi: 10.1016/j.radonc.2013.03.029. Epub 2013 May 14.


Background and purpose: In radiotherapy (RT) of prostate cancer the key organs at risk (ORs) - the rectum and the bladder - display considerable motion, which may influence the dose/volume parameters predicting for morbidity. In this study we compare motion-inclusive doses to planned doses for the rectum and bladder and explore their associations with prospectively recorded morbidity.

Materials and methods: The study included 38 prostate cancer patients treated with hypo-fractionated image-guided intensity-modulated RT that had an average of nine repeat CT scans acquired during treatment. These scans were registered to the respective treatment planning CT (pCT) followed by a new dose calculation from which motion-inclusive dose distributions were derived. The pCT volumes, the treatment course averaged volumes as well as the planned and motion-inclusive doses were associated with acute and late morbidity (morbidity cut-off: ≥ Grade 2).

Results: Acute rectal morbidity (observed in 29% of cases) was significantly associated with both smaller treatment course averaged rectal volumes (population median: 75 vs. 94 cm(3)) and the motion-inclusive volume receiving doses close to the prescription dose (2 Gy-equivalent dose of 76 Gy).

Conclusion: Variation in rectum and bladder volumes leads to deviations between planned and delivered dose/volume parameters that should be accounted for to improve the ability to predict morbidity following RT.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Humans
  • Male
  • Middle Aged
  • Motion
  • Prostatic Neoplasms / radiotherapy*
  • Radiotherapy Dosage
  • Radiotherapy Planning, Computer-Assisted
  • Rectum / radiation effects*
  • Urinary Bladder / radiation effects*