Strict bladder filling and rectal emptying during prostate SBRT: Does it make a dosimetric or clinical difference?
Open Access
- 16 October 2020
- journal article
- research article
- Published by Springer Science and Business Media LLC in Radiation Oncology
- Vol. 15 (1), 1-9
- https://doi.org/10.1186/s13014-020-01681-6
Abstract
To evaluate inter-fractional variations in bladder and rectum during prostate stereotactic body radiation therapy (SBRT) and determine dosimetric and clinical consequences. Eighty-five patients with 510 computed tomography (CT) images were analyzed. Median prescription dose was 40 Gy in 5 fractions. Patients were instructed to maintain a full bladder and empty rectum prior to simulation and each treatment. A single reviewer delineated organs at risk (OARs) on the simulation (Sim-CT) and Cone Beam CTs (CBCT) for analyses. Bladder and rectum volume reductions were observed throughout the course of SBRT, with largest mean reductions of 86.9 mL (19.0%) for bladder and 6.4 mL (8.7%) for rectum noted at fraction #5 compared to Sim-CT (P < 0.01). Higher initial Sim-CT bladder volumes were predictive for greater reduction in absolute bladder volume during treatment (ρ = − 0.69; P < 0.01). Over the course of SBRT, there was a small but significant increase in bladder mean dose (+ 4.5 ± 12.8%; P < 0.01) but no significant change in the D2cc (+ 0.8 ± 4.0%; P = 0.28). The mean bladder trigone displacement was in the anterior direction (+ 4.02 ± 6.59 mm) with a corresponding decrease in mean trigone dose (− 3.6 ± 9.6%; P < 0.01) and D2cc (− 6.2 ± 15.6%; P < 0.01). There was a small but significant increase in mean rectal dose (+ 7.0 ± 12.9%, P < 0.01) but a decrease in rectal D2cc (− 2.2 ± 10.1%; P = 0.04). No significant correlations were found between relative bladder volume changes, bladder trigone displacements, or rectum volume changes with rates of genitourinary or rectal toxicities. Despite smaller than expected bladder and rectal volumes at the time of treatment compared to the planning scans, dosimetric impact was minimal and not predictive of detrimental clinical outcomes. These results cast doubt on the need for excessively strict bladder filling and rectal emptying protocols in the context of image guided prostate SBRT and prospective studies are needed to determine its necessity.Keywords
Other Versions
This publication has 36 references indexed in Scilit:
- Stereotactic Body Radiation Therapy (SBRT) for clinically localized prostate cancer: the Georgetown University experienceRadiation Oncology, 2013
- Hypofractionated External-Beam Radiotherapy for Prostate CancerProstate Cancer, 2013
- Rectal Dose Constraints for Intensity Modulated Radiation Therapy of the ProstateAmerican Journal of Clinical Oncology, 2011
- Bladder extension variability during pelvic external beam radiotherapy with a full or empty bladderRadiotherapy and Oncology, 2007
- Stereotactic hypofractionated accurate radiotherapy of the prostate (SHARP), 33.5 Gy in five fractions for localized disease: First clinical trial resultsInternational Journal of Radiation Oncology*Biology*Physics, 2007
- Variability of bladder filling in patients receiving radical radiotherapy to the prostateRadiotherapy and Oncology, 2006
- Bladder filling variation during radiation treatment of prostate cancer: Can the use of a bladder ultrasound scanner and biofeedback optimize bladder filling?International Journal of Radiation Oncology*Biology*Physics, 2006
- Prostate position variability and dose–volume histograms in radiotherapy for prostate cancer with full and empty bladderInternational Journal of Radiation Oncology*Biology*Physics, 2006
- Variation in volumes, dose-volume histograms, and estimated normal tissue complication probabilities of rectum and bladder during conformal radiotherapy of T3 prostate cancerInternational Journal of Radiation Oncology*Biology*Physics, 1995
- Dosimetry guidelines to minimize urethral and rectal morbidity following transperineal I-125 prostate brachytherapyInternational Journal of Radiation Oncology*Biology*Physics, 1995