Dijkema Tim, Terhaard Chris H J, Roesink Judith M, Braam Pètra M, van Gils Carla H, Moerland Marinus A, Raaijmakers Cornelis P J
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands.
Int J Radiat Oncol Biol Phys. 2008 Nov 15;72(4):1101-9. doi: 10.1016/j.ijrobp.2008.02.059. Epub 2008 May 28.
To compare parotid gland dose-volume response relationships in a large cohort of patients treated with intensity-modulated (IMRT) and conventional radiotherapy (CRT).
A total of 221 patients (64 treated with IMRT, 157 with CRT) with various head-and-neck malignancies were prospectively evaluated. The distribution of tumor subsites in both groups was unbalanced. Stimulated parotid flow rates were measured before and 6 weeks, 6 months, and 1 year after radiotherapy. Parotid gland dose-volume histograms were derived from computed tomography-based treatment planning. The normal tissue complication probability (NTCP) model proposed by Lyman was fit to the data. A complication was defined as stimulated parotid flow ratio <25% of the pretreatment flow rate. The relative risk of complications was determined for IMRT vs. CRT and adjusted for the mean parotid gland dose using Poisson regression modeling.
One year after radiotherapy, NTCP curves for IMRT and CRT were comparable with a TD(50) (uniform dose leading to a 50% complication probability) of 38 and 40 Gy, respectively. Until 6 months after RT, corrected for mean dose, different complication probabilities existed for IMRT vs. CRT. The relative risk of a complication for IMRT vs. CRT after 6 weeks was 1.42 (95% CI 1.21-1.67), after 6 months 1.41 (95% CI; 1.12-1.77), and at 1 year 1.21 (95% CI 0.87-1.68), after correcting for mean dose.
One year after radiotherapy, no difference existed in the mean dose-based NTCP curves for IMRT and CRT. Early after radiotherapy (up to 6 months) mean dose based (Lyman) models failed to fully describe the effects of radiotherapy on the parotid glands.
比较接受调强放疗（IMRT）和传统放疗（CRT）的大量患者腮腺剂量-体积反应关系。
前瞻性评估了221例患有各种头颈恶性肿瘤的患者（64例接受IMRT，157例接受CRT）。两组肿瘤亚部位的分布不均衡。在放疗前以及放疗后6周、6个月和1年测量刺激后的腮腺流速。腮腺剂量-体积直方图源自基于计算机断层扫描的治疗计划。将Lyman提出的正常组织并发症概率（NTCP）模型拟合到数据中。并发症定义为刺激后的腮腺流速比<预处理流速的25%。使用泊松回归模型确定IMRT与CRT并发症的相对风险，并根据腮腺平均剂量进行调整。
放疗1年后，IMRT和CRT的NTCP曲线具有可比性，TD(50)（导致50%并发症概率的均匀剂量）分别为38 Gy和40 Gy。在放疗后6个月之前，校正平均剂量后，IMRT与CRT存在不同的并发症概率。6周后IMRT与CRT并发症的相对风险为1.42（95%CI 1.21-1.67），6个月后为1.41（95%CI；1.12-1.77），1年后为1.21（95%CI 0.87-1.68），校正平均剂量后。
放疗1年后，基于平均剂量的IMRT和CRT的NTCP曲线无差异。放疗早期（至6个月）基于平均剂量（Lyman）的模型未能充分描述放疗对腮腺的影响。
