Medical Physics Laboratory, Regina Elena Cancer Institute, Rome, Italy.
Clin Oncol (R Coll Radiol). 2012 Apr;24(3):e54-62. doi: 10.1016/j.clon.2011.11.006. Epub 2011 Dec 3.
To quantify the changes in dose as well as in the prediction of parotid gland toxicity due to anatomical changes during therapy of head and neck cancer patients.
Fifteen patients with advanced locoregional head and neck cancer, with no evidence of distant metastasis, were enrolled in a prospective study. All patients were treated with intensity-modulated radiotherapy. Multiple computed tomography scans were repeated at the end of each treatment week. The original treatment plans were copied to the per-treatment scans to create hybrid plans. The normal tissue complication probability (NTCP) was calculated assuming the end point to be grade ≥3 xerostomia according to the Radiation Therapy Oncology Group late toxicity scale.
The gross tumour volume dose coverage was slightly affected by the anatomical changes, whereas the mean dose (D(mean)) to the parotids changed from 26.1 ± 6.0 to 27.4 ± 7.4 Gy, with a mean increase of 0.22 Gy/treatment week. Consequently, the mean NTCP increased from 0.15 ± 0.06 to 0.18 ± 0.10, primarily due to a few patients exhibiting a marked increase. The absolute gross tumour volume shrinkage and the percentage parotids shrinkage were the best independent predictors for the NTCP variations.
On average, the increase in the parotids D(mean) as well as in NTCP during treatment is limited, and the observed variations were strongly patient-dependent.
定量评估由于头颈部癌症患者治疗过程中解剖结构变化导致的剂量变化以及腮腺毒性预测的变化。
本研究纳入了 15 例局部晚期头颈部癌症患者，这些患者无远处转移的证据，他们均接受了调强放疗。在每个治疗周结束时重复进行多次 CT 扫描。将原始治疗计划复制到每次治疗的扫描中，以创建混合计划。假设终点为根据放射治疗肿瘤学组晚期毒性量表出现≥3 级口干症，计算正常组织并发症概率（NTCP）。
肿瘤总体积剂量覆盖受解剖结构变化的轻微影响，而腮腺的平均剂量（Dmean）从 26.1±6.0 Gy 增加到 27.4±7.4 Gy，平均每周增加 0.22 Gy。因此，平均 NTCP 从 0.15±0.06 增加到 0.18±0.10，主要是由于少数患者的明显增加。肿瘤总体积绝对收缩和腮腺百分比收缩是 NTCP 变化的最佳独立预测因子。
在治疗过程中，腮腺的 Dmean 和 NTCP 的平均增加是有限的，并且观察到的变化强烈依赖于患者。
