Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan; Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-Universität, Munich, Germany.
Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan.
Int J Radiat Oncol Biol Phys. 2015 Feb 1;91(2):435-43. doi: 10.1016/j.ijrobp.2014.09.046.
This study compared normal tissue complication probability (NTCP) modeling of chronic gastrointestinal toxicities following prostate cancer treatment for 2 treatment modalities. Possible factors causing discrepancies in optimal NTCP model parameters between 3-dimensional conformal radiation therapy (3D-CRT) and intensity modulated RT (IMRT) were analyzed and discussed, including the impact of patient characteristics, image guidance, toxicity scoring bias, and NTCP model limitations.
Rectal wall dose-volume histograms of 1115 patients treated for prostate cancer under an adaptive radiation therapy protocol were used to model gastrointestinal toxicity grade ≥2 (according to Common Terminology Criteria for Adverse Events). A total of 457 patients were treated with 3D-CRT and 658 with IMRT. 3D-CRT patients were matched to IMRT patients based on various patient characteristics, using a propensity score-based algorithm. Parameters of the Lyman equivalent uniform dose and cut-off dose logistic regression NTCP models were estimated for the 2 matched treatment modalities and the combined group.
After they were matched, the 3D-CRT and IMRT groups contained 275 and 550 patients with a large discrepancy of 28.7% versus 7.8% toxicities, respectively (P<.001). For both NTCP models, optimal parameters found for the 3D-CRT groups did not fit the IMRT patients well and vice versa. Models developed for the combined data overestimated NTCP for the IMRT patients and underestimated NTCP for the 3D-CRT group.
Our analysis did not reveal a single definitive cause for discrepancies of model parameters between 3D-CRT and IMRT. Patient characteristics and bias in toxicity scoring, as well as image guidance alone, are unlikely causes of the large discrepancy of toxicities. Whether the cause was inherent to the specific NTCP models used in this study needs to be verified by future investigations. Because IMRT is increasingly used clinically, it is important that appropriate NTCP model parameters are determined for this treatment modality.
本研究比较了两种前列腺癌治疗模式下慢性胃肠道毒性的正常组织并发症概率（NTCP）建模。分析并讨论了导致 3 维适形放疗（3D-CRT）和调强放疗（IMRT）之间最佳 NTCP 模型参数差异的可能因素，包括患者特征、图像引导、毒性评分偏差和 NTCP 模型局限性。
采用自适应放疗方案治疗前列腺癌的 1115 例患者的直肠壁剂量-体积直方图，用于对胃肠道毒性 2 级（根据常见不良事件术语标准）进行建模。共有 457 例患者接受 3D-CRT 治疗，658 例患者接受 IMRT 治疗。3D-CRT 患者基于各种患者特征，采用倾向评分匹配算法与 IMRT 患者匹配。为 2 种匹配的治疗模式和组合组估计 Lyman 等效均匀剂量和截止剂量逻辑回归 NTCP 模型的参数。
匹配后，3D-CRT 和 IMRT 组分别包含 275 例和 550 例患者，毒性发生率分别为 28.7%和 7.8%，差异较大（P<0.001）。对于这两种 NTCP 模型，为 3D-CRT 组找到的最佳参数不太适合 IMRT 患者，反之亦然。为组合数据开发的模型高估了 IMRT 患者的 NTCP，低估了 3D-CRT 组的 NTCP。
我们的分析并未发现 3D-CRT 和 IMRT 之间模型参数差异的单一明确原因。患者特征和毒性评分偏差，以及单独的图像引导，不太可能是毒性差异较大的原因。该研究中使用的特定 NTCP 模型是否存在内在原因，需要进一步研究验证。由于 IMRT 在临床上越来越多地使用，因此确定这种治疗模式的适当 NTCP 模型参数非常重要。
