Audrey Li, Abstract Co-Author: Nothing to Disclose

Larry Pan, Presenter: Nothing to Disclose

For men undergoing definitive radiation treatment for prostate cancer it is known that the degree of bladder and rectal filling can significantly impact target movement and dose to normal structures. This has not been extensively studied for men undergoing post-operative radiation therapy for prostate cancer.Purpose/Objective: To determine the impact of a full or empty bladder on the dose volume histogram (DVH) for bladder and rectum for patients receiving post-operative radiation for prostate cancer. The specific objective was to determine which bladder state (full or empty) is optimal for these patients.

Forty consecutive eligible post-prostatectomy patients requiring adjuvant or salvage radiation therapy underwent CT simulation. Patients were scanned initially with a full bladder and then again after voiding (empty bladder). A plan was generated using a standard 4 field technique with standard shielding and 18 MV photons. In all cases, the dose was 64.8 Gy in 36 daily fractions. For each patient, the bladder and rectal volumes and DVHs were measured and differences were compared using the paired T-test statistical analysis.

Bladder volumes receiving high doses were significantly higher for the empty bladder. A statistically significant difference was found for the V61.5 and V32.4 of the bladder (p<0.0001) but not for the V64.8. The bladder D100 (p<0.0001), D50 (p<0.0001), D35 (p<0.001), D25 (p<0.008) and D15 (p<0.029) showed statistically significant differences favoring the full bladder state with lower overall doses for all volumes of bladder examined. For the rectum, no significant difference was seen for the V64.8, V61.5, V32.4, D25 or D15. However, a significant difference was found for the D100 (p<0.008), D50 (p<0.014) and D35 (p<0.022) showing lower overall doses for 100%, 50% and 35% of the rectal volume.

In this cohort of post-prostatectomy patients, analysis of the dose volume histograms for the organs at risk (bladder and rectum) favors the use of full bladder status for radiation therapy planning in order to minimize dose to these structures. Impact of bladder filling on prostate bed motion will be examined in future research.

Li, A, Pan, L, Full or Empty? Impact of Bladder Filling on Dose Volume Histograms for Post-Prostatectomy Radiation.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/7001631.html