Image-guided radiotherapy of the prostate using daily CBCT: the feasibility and likely benefit of implementing a margin reduction
Image-guided radiotherapy of the prostate using daily CBCT: the feasibility and likely benefit of implementing a margin reduction
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DOI：
10.1259/bjr.20140459
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发表时间：
2014-12-01
影响因子：
2.6
通讯作者：
Poynter, A.
中科院分区：
文献类型：
--
作者：
Maund, I. F.;Benson, R. J.;Poynter, A.
目的：探讨每日在线管锥束CT （online tube potential-cone beam CT， CBCT）图像引导在局部前列腺癌放疗中是否可以安全减小靶体积（PTV）边界，以及预测直肠毒性的预期收益。方法：随机选择18例患者，每周1次治疗前CBCT上对患者的前列腺靶体积（CTV2）和直肠进行划定。通过将这些轮廓转置到原始计划中，计算并组合每个患者的CTV2和直肠的剂量-体积直方图（DVH），以产生代表整个治疗过程中剂量的单个平均DVH。利用缩小的CTV2到PTV2切缘以及随后的直肠肿瘤控制概率（TCP）和正常组织并发症概率（NTCP）模拟的放射生物学影响来重新优化计划。结果：所有的CBCT图像都被认为具有足够的质量来识别CTV和直肠。当使用标准的5毫米CTV2到PTV2中心边缘的计划重新优化为4或3毫米边缘时，没有观察到TCP的损失。切缘缩小与直肠NTCP显著降低相关（5-4 mm, p < 0.05和5-3 mm， p < 0.01）。结论：使用CBCT每日在线图像引导，在不影响肿瘤控制的情况下，可以将CTV2至PTV2边缘缩小至3mm。因此，保留周围正常组织与减少预期的直肠毒性有关。知识的进步：减少保证金是可行的，而且可能是有益的。具有影像引导放射治疗能力的中心应考虑评估是否有可能在其研究所内缩小切缘。
Objective: To investigate whether planning target volume (PTV) margins may be safely reduced in radiotherapy of localized prostate cancer incorporating daily online tube potential-cone beam CT (CBCT) image guidance and the anticipated benefit in predicted rectal toxicity.Methods: The prostate-only clinical target volume (CTV2) and rectum were delineated on 1 pre-treatment CBCT each week in 18 randomly selected patients. By transposing these contours onto the original plan, dose-volume histograms (DVHs) for CTV2 and the rectum were each calculated and combined, for each patient, to produce a single mean DVH representative of the dose delivered over the treatment course. Plans were reoptimized using reduced CTV2 to PTV2 margins and the consequent radiobiological impact modelled by the tumour control probability (TCP) and normal tissue complication probability (NTCP) of the rectum.Results: All CBCT images were deemed of sufficient quality to identify the CTV and rectum. No loss of TCP was observed when plans using the standard 5-mm CTV2 to PTV2 margin of the centre were reoptimized with a 4- or 3-mm margin. Margin reduction was associated with a significant decrease in rectal NTCP (5-4 mm; p < 0.05 and 5-3 mm; p < 0.01).Conclusion: Using daily online image guidance with CBCT, a reduction in CTV2 to PTV2 margins to 3 mm is achievable without compromising tumour control. The consequent sparing of surrounding normal tissues is associated with reduced anticipated rectal toxicity.Advances in knowledge: Margin reduction is feasible and potentially beneficial. Centres with image-guided radiotherapy capability should consider assessing whether margin reduction is possible within their institutes.