Influence of Organ at Risk Definition on Rectal Dose-Volume Histograms in Patients with Prostate Cancer Undergoing External-Beam Radiotherapy

Abstract

Data from the literature on normal-tissue complication probability (rectal bleeding) refer to different rectal contours. When applying dose restrictions to the rectum, contouring becomes a significant factor that determines the risk of rectal toxicity. The results of this study show that different ways of rectal contouring significantly influence doses to the rectum. The influence of organ at risk contouring should be considered thoroughly in conformal radiotherapy of prostate cancer patients, especially in dose escalation studies. It is recommended to calculate the doses for absolute rectal volumes and correlate these data with toxicity in order to be able to achieve comparable results among different institutions.

Influence of Rectum Delineation (Rectal Volume vs. Rectal Wall) on IMRT Treatment Planning of the Prostate

“…However, both DVH parameters of the entire RV, wall including the rectal lumen [1,5,8,11,26], and the RW [2,12,13,25] have been reported to be correlated to late rectal toxicity. The current literature does not allow a judgment whether DVH parameters of the RW or the RV should be used to estimate the risk of late rectal toxicity.…”

Comparison of different contouring definitions of the rectum as organ at risk (OAR) and dose–volume parameters predicting rectal inflammation in radiotherapy of prostate cancer: which definition to use?

“…[1][2][3][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Distinctive anatomical features characterized the first nine definitions of the rectum as an OAR, whereas the last four were functional definitions, in which the rectum was exclusively considered with regard to the PTV. All the contouring throughout the entire study was performed by one experienced consultant (RMH) to exclude interobserver variability.…”

“…So far, there are limited data on the correlation between differences in the definition of the rectum as an OAR and the clinical occurrence of side effects. [10][11][12] The present study evaluated the influence of different rectal OAR definitions on the prediction of acute and subacute rectal toxicity. The aim is the identification of an intuitive and robust rectum definition leading to DHV parameters that are correlated with rectal toxicity.…”

Organ Movements and Dose Exposures in Teletherapy of Prostate Cancer using a Rectal Balloon

“…PTV 2 included the prostate gland with a defined safe- To keep influence of the kind of contouring upon the measured organ exposure as small as possible, and to measure correctly [5,16], the complete rectum, including the lumen, the rectal mucosa without the lumen with a safety margin of 3 mm and a division of this rectal mucosa in the rectal middle to anterior rectal wall and posterior rectal wall were contoured as organs at risk. The urinary bladder was also declared as organ at risk.…”