Chera Bhishamjit S, Vargas Carlos, Morris Christopher G, Louis Debbie, Flampouri Stella, Yeung Daniel, Duvvuri Srividya, Li Zuofeng, Mendenhall Nancy Price
University of Florida, Department of Radiation Oncology, Gainesville, FL 32206, USA.
Int J Radiat Oncol Biol Phys. 2009 Nov 15;75(4):994-1002. doi: 10.1016/j.ijrobp.2009.01.044. Epub 2009 Jul 18.
To compare dose distributions in targeted tissues (prostate, seminal vesicles, pelvic regional nodes) and nontargeted tissues in the pelvis with intensity-modulated radiotherapy (IMRT) and forward-planned, double-scattered, three-dimensional proton radiotherapy (3D-PRT).
IMRT, IMRT followed by a prostate 3D-PRT boost (IMRT/3D-PRT), and 3D-PRT plans were created for 5 high-risk prostate cancer patients (n = 15 plans). A 78-CGE/Gy dose was prescribed to the prostate and proximal seminal vesicles and a 46-CGE/Gy was prescribed to the pelvic nodes. Various dosimetric endpoints were compared.
Target coverage of the prostate and nodal planning target volumes was adequate for all three plans. Compared with the IMRT and IMRT/3D-PRT plans, the 3D-PRT plans reduced the mean dose to the rectum, rectal wall, bladder, bladder wall, small bowel, and pelvis. The relative benefit of 3D-PRT (vs IMRT) at reducing the rectum and rectal wall V5-V40 was 53% to 71% (p < 0.05). For the bladder and bladder wall, the relative benefit for V5 to V40 CGE/Gy was 40% to 63% (p < 0.05). The relative benefit for reducing the volume of small bowel irradiated from 5 to 30 CGE/Gy in the 3D-PRT ranged from 62% to 69% (p < 0.05). Use of 3D-PRT did not produce the typical low-dose "bath" of radiation to the pelvis seen with IMRT. Femoral head doses were higher for the 3D-PRT.
Use of 3D-PRT significantly reduced the dose to normal tissues in the pelvis while maintaining adequate target coverage compared with IMRT or IMRT/3D-PRT. When treating the prostate, seminal vesicles, and pelvic lymph nodes in prostate cancer, proton therapy may improve the therapeutic ratio beyond what is possible with IMRT.
比较调强放射治疗（IMRT）与正向计划、双散射三维质子放疗（3D-PRT）在靶向组织（前列腺、精囊、盆腔区域淋巴结）及盆腔非靶向组织中的剂量分布。
为5例高危前列腺癌患者制定IMRT、IMRT序贯前列腺3D-PRT推量（IMRT/3D-PRT）及3D-PRT计划（共15个计划）。前列腺和近端精囊的处方剂量为78 CGE/Gy，盆腔淋巴结的处方剂量为46 CGE/Gy。比较了各种剂量学终点。
三种计划对前列腺和淋巴结计划靶区的靶区覆盖均足够。与IMRT和IMRT/3D-PRT计划相比，3D-PRT计划降低了直肠、直肠壁、膀胱、膀胱壁、小肠和盆腔的平均剂量。3D-PRT（与IMRT相比）在降低直肠和直肠壁V5-V40方面的相对获益为53%至71%（p<0.05）。对于膀胱和膀胱壁，V5至V40 CGE/Gy的相对获益为40%至63%（p<0.05）。3D-PRT在减少5至30 CGE/Gy照射的小肠体积方面的相对获益为62%至69%（p<0.05）。3D-PRT的使用未产生IMRT常见的盆腔低剂量“浴盆”样辐射。3D-PRT的股骨头剂量更高。
与IMRT或IMRT/3D-PRT相比，3D-PRT的使用在维持足够靶区覆盖的同时，显著降低了盆腔正常组织的剂量。在治疗前列腺癌的前列腺、精囊和盆腔淋巴结时，质子治疗可能会提高治疗比，超出IMRT所能达到的水平。
