Room: Exhibit Hall | Forum 7
Purpose: Endorectal balloons are increasingly used in prostate cancer radiotherapy to restrict both inter and intra fractional prostate motion and for reducing rectal radiation toxicity. This retrospective study was conducted to determine the accuracy in daily positional reproducibility of two types of commercially available endorectal balloons from RadiaDyne used for the treatment of prostate cancer patients in proton therapy.
Methods: A total of 12 prostate patients were included in this study who received daily proton radiation therapy with endorectal balloons (6 treated with the old ImmobiLoc 60cc balloon and the other 6 treated using the new IsoLoc 60cc balloon). SmartAdapt (Varian/Eclipse) tool was utilized to evaluate positional deviation of both types of endorectal balloons with respect to the centroid of fiducialâ€™s placed in prostate. The endorectal balloon and fiducial markers were drawn on weekly cone-beam CT (CBCT) and the distance from centroid of the fiducials to the centroid of the balloon was noted for each of these patients in all the three translational directions.
Results: 84 CBCT study sets (7 CBCT for each patient) were assessed to predict the positional reproducibilityâ€™s of both type of balloons. The average three dimensional distance between centroid of the fiducials to that of the balloon for ImmobiLoc patients was 3.86 Â± 0.37 cm and for IsoLoc patients was found to be 3.69 Â± 0.20 cm. Figure: 1 shows the daily deviation in centroid distances for both type of endorectal balloons. Figure: 2 and 3 also illustrates difference in daily positions from the mean of each of their respective translational distances between the centroid of the fiducials and both type of balloons.
Conclusion: Both average variation in their centroid distances and daily balloon positional differences from the mean-translational distances between the centroids shows IsoLoc balloons are more reproducible in the daily setup of prostate treatments.