Optimizing prostate intensity-modulated radiation therapy (IMRT): Do stricter constraints produce better dosimetric results?

PURPOSE: Intensity Modulated Radiation Therapy (IMRT) is considered by many to be the standard of care in the delivery of external beam radiotherapy treatments to the prostate. The purpose of this study is to determine if using criteria stricter than that used in the current randomized trials will provide dosimetric improvement. MATERIALS AND METHODS: Treatment plans were produced for ten patients utilizing the dose constraints recommended by the large randomized RTOG 0415 protocol and more restrictive restraints similar to those employed by a large cancer center. RESULTS: The restrictive plans show consistently lower doses to the rectal and bladder volumes of interest. They also show a significant reduction in dose to the penile bulb. PTV coverage was more homogeneous for the protocol based plans. CONCLUSIONS: It is clear from our analysis that general constraints, while easily met, don't result in the maximal benefits of Intensity Modulated Radiation Therapy in sparing the rectum. The trade off is with more homogeneity in the target volume. Further research is needed to identify the ideal balance between reducing toxicity and sacrificing tumor coverage.