Comparison of effect of rectal volume delineation methods on dose constraint endpoints in the treatment of prostate cancer with intensity-modulated radiation therapy

Identifying a reliable method of rectal volume delineation (RVD) for prostate cancer treatment planning using intensity-modulated radiation therapy (IMRT) is invaluable for clinical and investigational purposes. We analyzed rectal dose constraint outcomes utilizing commonly used RVD methods. Sixty-two prostate cancer patients treated with IMRT from August 2008 to March 2010 were reviewed. RVD either included the entire rectal volume (ERV) or limited the volume to a 3 mm rectal wall (3 MM). V50 ,the percentage of rectal volume receiving 50 Gy, V65, V70, and V75.6 were determined and analyzed for differences. We analyzed factors including definitive and postoperative treatment, rectal volume, and length. For definitive treatment, using ERV, the mean rectal V50, V65, V70, and V75.6 was 41.3, 21.6, 15.1, and 7.0 %, respectively. Using 3 MM, the mean V50, V65, V70, and V75.6 was 37.3, 23.4, 18.5, and 10.3 %, respectively. The V65, V70, and V75.6 were significantly lower in ERV than 3 MM (p