Is IMRT needed to spare the rectum when pelvic lymph nodes are part of the initial treatment volume for prostate cancer?
Is IMRT needed to spare the rectum when pelvic lymph nodes are part of the initial treatment volume for prostate cancer?
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DOI：
10.1016/j.ijrobp.2005.06.026
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发表时间：
2006-01-01
影响因子：
7
通讯作者：
Bayouth, JE
中科院分区：
文献类型：
--
作者：
Sanguineti, G;Cavey, ML;Bayouth, JE
目的：评估4野箱式技术（4-field box technique，4 FBT）及其沿着技术改进是否是一种适当的方法，可用于局部前列腺癌患者行全盆腔放疗后前列腺增强放疗的直肠保留和靶区覆盖，以及是否需要调强放疗（intensitymodulated radiation，IMRT）。方法和材料：对于8例患者，生成了31个计划，每个计划在一个或多个特征上不同，包括处方（剂量/体积）和/或技术因素。对于后者，提出了几种试图减少直肠照射量的“解决方案”，包括修改4FBT和使用序贯IMRT。我们构建了一个包含248个计划的数据库，这些计划在V50、V60、V65、V70、V75和V75.6时进行了测试，以确定其满足一系列直肠剂量体积限制的能力。采用多因素logistic回归分析确定与终点独立相关的因素。结果：在多因素Logistic回归分析中，直肠阻断和调强放疗均是盆腔和增强期直肠剂量-体积约束的独立预测因素，且相关风险密切。然而，平均而言，在全盆腔放疗过程中，4FBT侧野的部分直肠阻断导致约3%的盆腔淋巴结PTV在等剂量95%之外; 8例患者中只有2例的盆腔淋巴结PTV覆盖与全盆腔IMRT相似。相反，在适形增强的最后3个部分期间阻断直肠显示了与IMRT增强所实现的类似的前列腺PTV的剂量测定覆盖。有趣的是，患者的解剖结构是直肠保留的最强预测因素。最后，前列腺边缘的大小，以产生PTV也独立相关的概率，以满足直肠剂量体积constrains.Conclusion：在剂量范围为70-76戈伊的前列腺，调强放疗和标准技术是同样有效的，在满足直肠剂量体积的限制。然而，全骨盆调强放射治疗可能是更可取的标准技术，其略优于上级PTV覆盖。(c)2006年爱思唯尔公司
Purpose: To assess whether a 4-field box technique (4FBT), along with its technical refinements, is an adequate approach in terms of rectal sparing and target coverage for patients with localized prostate cancer undergoing whole-pelvic radiotherapy followed by a prostate boost and whether or not intensity-modulated radiotherapy (IMRT) is needed.Methods and Materials: For 8 patients, 31 plans were generated, each of them differing in one or more features, including prescription (dose/volume) and/or technical factors. For the latter, several "solutions" to try to reduce the amount of irradiated rectal volume were addressed, including modifications of the 4FBT and the use of sequential IMRT. We constructed a database with 248 plans that were tested for their ability to meet a series of rectal dose-volume constraints at V50, V60, V65, V70, V75, and V75.6. Multivariate logistic regression was used to identify factors independently associated with the end point. Successful solutions were also compared in terms of coverage of both pelvic node and prostate planning target volume (PTV) by isodose 95%.Results: At multivariate logistic regression, both rectal blocking and IMRT were independent predictors of the probability of meeting rectal dose-volume constraints during the pelvic and boost phases of treatment with close relative risks. However, on average, partial rectal blocking on lateral fields of 4FBT during whole-pelvic radiotherapy resulted in about 3% of pelvic node PTV being outside isodose 95%; only 2 of 8 patients had the pelvic nodal PTV covered similarly to what was achieved by whole-pelvis IMRT. Conversely, blocking the rectum during the last 3 fractions of the conformal boost showed a dosimetric coverage of prostate PTV similar to that achieved by IMRT boost. Interestingly, patient anatomic configuration was the strongest predictor of rectal sparing. Finally, the size of prostate margins to generate PTV was also independently associated with the probability of meeting rectal dose-volume constraints.Conclusion: In the dose range of 70-76 Gy to the prostate, IMRT and standard techniques are equally effective in meeting rectal dose-volume constraints. However, whole-pelvis IMRT might be preferable to standard techniques for its slightly superior PTV coverage. (c) 2006 Elsevier Inc.