Influence Of Bladder Distension Control On Postoperative IMRT In Rectal Cancer Patients Using Belly Board

ObjectiveThis present study was to investigate the correlation between factors with diarrheadegree, and compared the effects of the combination of belly board with or without bladderirrigation, to evaluate the influence on the dose-volume histograms (DVHs) of organs atrisk (OARs), especially small bowel and bladder, to find an optimal technique forpostoperative radiotherapy of rectal cancer patients and guide the development ofindividualized treatment.Materials and methodsOur study design was a prospective study. This study was approved by ShandongCancer Hospital and all patients signed an informed consent. A total of78patients withhistologically documented rectal cancer who treated with postoperative concurrentradiochemotherapy between October2010and September2011at Shandong TumorHospital were included. All patients received a total radiation dose of50.4Gy given in28fractions (1.8Gy per fraction) using intensity modulated radiotherapy, andsimultaneous received5-FU-based (FolFox scheme) chemotherapy during the period ofradiotherapy. As to60patients, correlation between factors and diarrhea was accessed.Differences were evaluated in a univariate manner. Potential prognostic factors found tobe significant in the univariate analysis were evaluated in a multivariate analysis, whichwas carried out with logistic regression analysis. Another18patients were asked toempty their bladders, and drink oral contrast solution (meglumine diatrizoate) before theCT scan. Then the patient was asked to maintain an upright position allowing time tovisualize the small bowel and distend the bladder. Patients completed self-assessmentusing a scale of1–4for bladder comfort. A score of1indicated the patient’s bladder wascomfortably full and a score of4was an indicator that the bladder was uncomfortablyfull. Patients were asked to lay prone on the belly board and start to scan when the score was3(GroupⅠ). The first set of CT was taken. Then the patient underwent urethralcatheterization and the urine volume (VU1) was recorded within10minutes. The patientwas instructed in bladder distension techniques and were told to have a full bladder fordaily treatment. The second set of CT scans (Group Ⅱ) was taken4weeks later using asame method and underwent urethral catheterization. Then VU1ml normal salinesolution was injected into urinary bladder via urethral catheter to distend the bladder.Then the patient was scanned (Group Ⅲ). All target volumes were contoured andreviewed for each slice. The identified organ volumes and the targets in3plans wereensured to more or less equal. IMRT planning was performed, the prescribed radiationdose (50.4Gy) was normalized to the isodose surface. Radiation dose of PTV and criticalorgans were all within limits. Dose-volume histograms (DVHs) were computed for allplans. All data were analyzed for different groups using Wilcoxon sign rank test and/orFriedman test. All tests were two-sided and analyzed using SPSS17.0programs. A pvalue of <0.05was considered to indicate a significant difference.Results1The univariate analysis indicated that gender, BMI index, surgery method andirradiated small bowel volume were associated significantly with diarrhea degree. Themultivariate logistic regression analysis showed that surgery method and irradiated smallbowel volume was independent factors associated significantly with diarrhea degree.2Compare the volume of regions of interest: The volumes of PTV and CTV wereequal for all three groups. In group Ⅱ, the volume of bladder significantly reduced, themean reduction of bladder volume compared with groupⅠwas142.22cm3; the smallbowel volumes increased significantly, the mean increment of small bowel in group Ⅱcompared with groupⅠwas159.01cm3. There was no significant difference betweengroupⅠand Ⅲ. Statistical analyze showed there’s a correlation between the reduction ofbladder and the increment of small bowel, r=0.683, P<0.05.3Compare the bladder and small bowel volume within every isodose level: In group Ⅱ, the small bowel volume within every isodose level and the mean relative bladdervolume within30Gy,40Gy and50Gy isodose level was increased significantly, P<0.05.There was no significant difference between the bladder and small bowel volume withinevery isodose level in groupⅠand Ⅲ.4There is no statistical significance between the maximum radiation dose of smallbowel and bladder in all groups. While the mean radiation dose of small bowel andbladder is increased in group Ⅱ compared to group Ⅰand group Ⅲ, P<0.05.Conclusions1Surgery method and irradiated small bowel volume was independent factorsassociated significantly with diarrhea degree.2The bladder volume declined significantly during the course of radiotherapy.Hence an increment of irradiated small bowel volume. The mean radiation dose of smallbowel and bladder is increased in group Ⅱ compared. There was no significantdifference between groupⅠand Ⅲ for every parameters.3Bladder irrigation is a feasible method to guarantee a consistent bladder volumeand reduce the irradiated small bowel volume.