Prostate radiotherapyEmptying the rectum before treatment delivery limits the variations of rectal dose–volume parameters during 3DCRT of prostate cancer
Section snippets
Patients and treatment protocol
Ten patients with localized carcinoma of the prostate were enrolled in the study on a voluntary basis after written informed consent. The first step was a planning CT scan (CT0), followed by two CT scans per week throughout the treatment period (treatment CT scans, CT1−n) performed immediately before (i.e. within 30 min) treatment delivery.
The number of treatment CT scans was lower than those planned in some patients (11–14), due to organizational problems. Therefore, a total of 126 treatment CT
Variations of rectum volumes and shapes
Both BEV and volume analysis showed a slight systematic variation of the rectal volume between planning and treatment.
Fig. 2(a and b) shows the variations of rectum/rectum wall volume at CT0 and the average rectum/rectum wall volume during planning. It was observed that the average rectal volume during therapy was larger than at the planning CT, in 8/10 patients (Pts.1–8), with an average rectal volume increase of around 8 cm3 (range: 2–20 cm3). The Wilcoxon test showed that this increase was
Rectal volume variation
A number of studies have dealt with the problem of assessing the impact of rectum motion due to variable filling during 3DCRT for prostate cancer. Emphasizing that this point is crucial so as to be able to define appropriate margins to generate the PTV accurately, thus minimizing the risk of geographical miss. Values of systematic and random shifts may be influenced by a number of parameters, such as the degree of filling of the bladder/rectum during simulation and therapy as well as the
Conclusions
These data obtained in this study confirm the impact rectum motion has on rectum DVH, including filling and that of the rectum wall (DVH and DWH, respectively) during 3D-conformal radiotherapy (3DCRT) for localized prostate cancer in a scenario where the rectum is carefully emptied during simulation and therapy. The authors are of the opinion that the adoption of the safe and simple practice of emptying the rectum during CT-simulation and therapy would reduce the impact of organ motion on
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