McLaughlin P W, Wygoda A, Sahijdak W, Sandler H M, Marsh L, Roberson P, Ten Haken R K
Department of Radiation Oncology, The University of Michigan, Ann Arbor, USA.
Int J Radiat Oncol Biol Phys. 1999 Sep 1;45(2):407-13. doi: 10.1016/s0360-3016(99)00207-2.
The relative value of prone versus supine positioning and axial versus nonaxial beam arrangements in the treatment of prostate cancer remains controversial. Two critical issues in comparing techniques are: 1) dose to critical normal tissues, and 2) prostate stabilization.
Ten patients underwent pretreatment CT scans in one supine and two prone positions (flat and angled). To evaluate normal tissue exposure, prostate/seminal vesicle volumes or prostate volumes were expanded 8 mm and covered by the 95% isodose surface by both 6-field axial and 4-field nonaxial techniques. A total of 280 dose-volume histograms (DVHs) were analyzed to evaluate dose to rectal wall and bladder relative to patient position and beam arrangement. A CT scan was repeated in each patient after 5 weeks of treatment. Prostate motion was assessed by comparing early to late scans by three methods: 1) center of mass shift, 2) superior pubic symphysis to anterior prostate distance, and 3) deviation of the posterior surface of the prostate.
For prostate (P) or prostate/seminal vesicle (P/SV) treatments, prone flat was advantageous or equivalent to other positions with regard to rectal sparing. The mechanism of rectal sparing in the prone position may be related to a paradoxical retraction of the rectum against the sacrum, away from the P/SV. Although there was no clear overall preference for beam arrangement, substantial improvements in rectal sparing could be realized for individual patients. In this limited number of patients, there was no convincing evidence prostate position was stabilized by prone relative to supine position.
Prone flat positioning was advantageous over other positions and beam arrangements in rectal sparing. This study suggests that patient position is a more critical a factor in conformal therapy than beam arrangement, and may improve the safety of dose escalation.
在前列腺癌治疗中，俯卧位与仰卧位以及轴向与非轴向射束排列的相对价值仍存在争议。比较不同技术时的两个关键问题是：1）关键正常组织的剂量，以及2）前列腺的稳定性。
10名患者在一个仰卧位和两个俯卧位（平卧位和斜卧位）进行了治疗前CT扫描。为评估正常组织的受照情况，将前列腺/精囊体积或前列腺体积扩大8mm，并通过6野轴向和4野非轴向技术用95%等剂量面覆盖。共分析了280个剂量体积直方图（DVH），以评估相对于患者体位和射束排列的直肠壁和膀胱剂量。在治疗5周后，对每位患者重复进行CT扫描。通过三种方法比较早期和晚期扫描来评估前列腺运动：1）质心移位，2）耻骨联合上缘至前列腺前缘的距离，以及3）前列腺后表面的偏差。
对于前列腺（P）或前列腺/精囊（P/SV）治疗，俯卧平卧位在直肠保护方面优于或等同于其他体位。俯卧位直肠保护的机制可能与直肠向骶骨方向的反常回缩有关，远离P/SV。虽然在射束排列方面没有明确的总体偏好，但个别患者在直肠保护方面可实现显著改善。在这一有限数量的患者中，没有令人信服的证据表明俯卧位相对于仰卧位能稳定前列腺位置。
俯卧平卧位在直肠保护方面优于其他体位和射束排列。本研究表明，在适形治疗中，患者体位比射束排列更关键，可能会提高剂量递增的安全性。
