Department of Radiation Physics, Oncology and Hematology Hospital, Maadi Armed Forces Medical Compound, Cairo, Egypt.
Department of Radiotherapy, National Cancer Institute, Cairo University, Giza, Egypt.
Indian J Cancer. 2020 Oct-Dec;57(4):388-392. doi: 10.4103/ijc.IJC_555_18.
To evaluate the pros and cons of 9-field intensity modulated radiotherapy (IMRT) compared to 7-field IMRT in the treatment of nasopharyngeal carcinoma (NPC).
Ten NPC patients were treated with 7F-IMRT and 9F-IMRT. A dose prescription of 70 Gy was delivered in 35 fractions to gross planning target volume (PTV1). Plan verification was performed via 2D-array and film dosimetry. Dose-Volume Histogram (DVH) parameters were used to evaluate the quality of IMRT plans.
Dose data for the investigated planning techniques obeyed the Radiation Therapy Oncology Group (RTOG) protocol no. 0615. The dose delivered to PTV1 and organs-at-risk (OARs) for 9F-IMRT was significantly better than 7F-IMRT, except for OARs which were at a distance from PTV1, such as eyes, optical nerves, and chiasma. Ninety five percent of PTV1 was covered by more than 95% of the prescribed dose (67.75 ± 1.1 Gy and 68.57 ± 1.2 Gy for 7F-IMRT and 9F-IMRT, respectively). The maximum dose to 1% of brainstem was 50.06 ± 2.7 Gy and 47.75 ± 2.6 Gy for 7F-IMRT and 9F-IMRT, respectively. Dose verification showed good agreement with treatment planning system with a maximum deviation for 2D-array of 2.16% ± 0.86 and 1.73% ± 0.33 for 7F-IMRT and 9F-IMRT, respectively. Similarly, radiochromic film reported maximum dose deviations of 3.38% ± 1.68 and 2.77% ± 1.3, respectively.
9F-IMRT provides better homogenous dose to PTV1 and more sparing of OARs over 7F-IMRT for NPC patients, except for OARs which are are a distance from PTV1.
评估 9 野强度调制放疗（IMRT）与 7 野 IMRT 治疗鼻咽癌（NPC）的优缺点。
对 10 例 NPC 患者分别采用 7F-IMRT 和 9F-IMRT 治疗。大体肿瘤靶区（PTV1）给予 70Gy/35 次剂量。通过二维矩阵和胶片剂量测定进行计划验证。剂量-体积直方图（DVH）参数用于评估 IMRT 计划质量。
所研究的计划技术的剂量数据符合放射治疗肿瘤学组（RTOG）协议号 0615。9F-IMRT 给予 PTV1 和危及器官（OARs）的剂量明显优于 7F-IMRT，除了远离 PTV1 的 OARs 如眼睛、视神经和视交叉。95%的 PTV1 被超过 95%的规定剂量覆盖（7F-IMRT 和 9F-IMRT 分别为 67.75±1.1Gy 和 68.57±1.2Gy）。脑干 1%的最大剂量分别为 50.06±2.7Gy 和 47.75±2.6Gy。剂量验证与治疗计划系统吻合良好，二维矩阵最大偏差分别为 2.16%±0.86%和 1.73%±0.33%，7F-IMRT 和 9F-IMRT。同样，放射色胶片报告的最大剂量偏差分别为 3.38%±1.68%和 2.77%±1.3%。
9F-IMRT 为 NPC 患者提供了更好的 PTV1 均匀剂量，对 OARs 的保护作用优于 7F-IMRT，除了远离 PTV1 的 OARs。
