Fischer-Valuck Benjamin W, Chundury Anupama, Gay Hiram, Bosch Walter, Michalski Jeff
Washington University School of Medicine, Department of Radiation Oncology, St. Louis, Missouri.
Washington University School of Medicine, Department of Radiation Oncology, St. Louis, Missouri; Washington University Advanced Technology QA Center, St. Louis, Missouri.
Pract Radiat Oncol. 2017 May-Jun;7(3):195-202. doi: 10.1016/j.prro.2016.10.004. Epub 2016 Oct 17.
Hydrogel prostate-rectum spacers, biomaterials placed between the prostate and rectum, continue to gain interest as a method to reduce or limit rectal dose during dose escalated prostate cancer radiation therapy. Because the spacer is initially injected into the perirectal space as a liquid, the final distribution can vary. The purpose of this study was to evaluate hydrogel spacer (SpaceOAR system) implantation and distribution from a recent prospective randomized control trial and correlate spacer symmetry with rectal dose reduction as well as rectal wall infiltration (RWI) to acute and late toxicity.
T2-weighted magnetic resonance imaging sets of 149 patients enrolled in a prospective clinical trial who received transperineal spacer injection were assessed for hydrogel spacer midline symmetry and RWI using a semiqualitative scoring system. Symmetry was then correlated to rectal dose reduction using a Student t test (1-tailed, paired), whereas a Fisher exact test was used to correlate RWI with acute and late rectal toxicity. All patients had control treatment plans created before spacer injection.
Hydrogel spacer was symmetrically placed at midline for 71 (47.7%) patients at the prostate midgland as well as 1 cm superior and inferior to midgland. The remaining 78 (50.9%) patients had some level of asymmetry, with only 2 (1.3%) having far lateral distribution (ie, >2 cm) of hydrogel spacer. As the hydrogel spacer became more asymmetric, the level of rectal dose reduction relative to their control plans decreased. However, all but the most asymmetrical 1.3% had significant rectal dose reduction (P < .05). Rectal wall hydrogel spacer infiltration was seen in 9 (6.0%) patients. There was no correlation between RWI and procedure-related adverse events or acute/late rectal toxicity.
Significant reduction of rectal dose can still be achieved even in the setting of asymmetric hydrogel spacer placement. RWI does not correlate with patient complications.
水凝胶前列腺 - 直肠间隔物作为一种在前列腺癌剂量递增放疗期间减少或限制直肠剂量的方法，作为置于前列腺和直肠之间的生物材料，持续受到关注。由于间隔物最初是以液体形式注入直肠周围间隙，其最终分布可能会有所不同。本研究的目的是评估水凝胶间隔物（SpaceOAR系统）在最近一项前瞻性随机对照试验中的植入和分布情况，并将间隔物的对称性与直肠剂量减少以及直肠壁浸润（RWI）与急性和晚期毒性相关联。
对149名参加前瞻性临床试验并接受经会阴间隔物注射的患者的T2加权磁共振成像进行评估，使用半定性评分系统评估水凝胶间隔物的中线对称性和RWI。然后使用学生t检验（单尾，配对）将对称性与直肠剂量减少相关联，而使用Fisher精确检验将RWI与急性和晚期直肠毒性相关联。所有患者在间隔物注射前都制定了对照治疗计划。
71名（47.7%）患者的水凝胶间隔物在前列腺中叶以及中叶上下1 cm处对称放置。其余78名（50.9%）患者存在一定程度的不对称，只有2名（1.3%）患者的水凝胶间隔物分布在远外侧（即>2 cm）。随着水凝胶间隔物变得更加不对称，相对于对照计划的直肠剂量减少水平降低。然而，除了最不对称的1.3%患者外，所有患者的直肠剂量均有显著减少（P <.05）。9名（6.0%）患者出现直肠壁水凝胶间隔物浸润。RWI与手术相关不良事件或急性/晚期直肠毒性之间无相关性。
即使在水凝胶间隔物放置不对称的情况下，仍可显著降低直肠剂量。RWI与患者并发症无关。
