Department of Physics, Faculty of Science, Helwan University, Egypt; Baghdad Center for Radiotherapy and Nuclear Medicine, Medical City, Iraq.
Clinical oncology, Faculty of Medicine, Suze University, Egypt.
J Med Imaging Radiat Sci. 2023 Sep;54(3):473-480. doi: 10.1016/j.jmir.2023.07.002. Epub 2023 Jul 21.
Volumetric Modulated Arc Therapy (VMAT) is an option for the delivery of Radiotherapy treatment technique for pediatric nasopharyngeal cancer, VMAT is the most common treatment technique for pediatric nasopharyngeal cancer. The use of a combination of both biological and physical parameters in VMAT planning optimization may produce better target coverage and sparing of critical organs. This work was to compare Biological Cost Functions (BCFs) and Physical Cost Functions (PCFs) in the VMAT of pediatric nasopharyngeal cancer patients.
VMAT plans for 20 nasopharyngeal pediatric cancer patients were created using Monaco 5.11® treatment planning system (TPS). Three VMAT plans were retrospectively generated for each patient using BCFs, PCFs and mixed plan with a total dose of 61.2 Gy in 34 fractions to planning target volume (PTV). All plans were adjusted to deliver 95% of the prescribed dose to 95% of the PTV. The calculated plans were qualitatively and quantitatively evaluated using the dose-volume histogram (DVH).
The coverage of the target and the maximum dose for the three plans were nearly the same, and better sparing was achieved in the serial organs (spinal cord and brain stem) with PCFs. On the contrary, more dose spring was observed using the BCFs in the organs at risk (OARs) that were not involved in the dose optimization, such as the optic nerve maximum dose, with a significant p-value (0.035 and 0.0001) respectively. Using the PCFs, both parotids received a lower mean dose, but not for the oral cavity, which had a lower mean dose using BCFs (p=<0.0001). The same values of tumor control probability (TCP) were found for both cost functions in PTVs and normal tissue complications probability (NTCP) (99%). The values reported were as follows: spinal cord = 0.5%, brain stem = 19.1%, and brain = 90.7% for BCFs, compared to spinal cord = 0.3%, brain stem = 14.9%, and brain = 90.7% for PCFs. The delivery time was found to be less in BCFs (p=0.005).
The BCFs are superior to the PCFs in conformity index and time of radiation delivery. However, PCFs were better at dose sparing for the serial organs and achieving a sharper falloff dose around the involved volumes. A patient-specific clinical compromise is recommended to gain the best plan that meets the clinical goals.
容积调强弧形治疗（VMAT）是儿科鼻咽癌放射治疗技术的一种选择，VMAT 是儿科鼻咽癌最常见的治疗技术。在 VMAT 计划优化中使用生物和物理参数的组合可能会产生更好的靶区覆盖和关键器官的保护。这项工作旨在比较生物成本函数（BCF）和物理成本函数（PCF）在儿科鼻咽癌患者的 VMAT 中的应用。
使用 Monaco 5.11®治疗计划系统（TPS）为 20 名鼻咽癌儿科患者创建 VMAT 计划。每个患者分别用 BCF、PCF 和混合计划（总剂量为 61.2Gy，分 34 次）生成 3 个 VMAT 计划，以计划靶区（PTV）。所有计划均调整为将 95%的处方剂量输送至 95%的 PTV。使用剂量-体积直方图（DVH）对计算出的计划进行定性和定量评估。
三个计划的靶区覆盖和最大剂量几乎相同，PCF 能更好地保护连续器官（脊髓和脑干）。相反，在未参与剂量优化的危及器官（OAR）中，BCF 观察到更多的剂量爆发，视神经最大剂量的 p 值分别为 0.035 和 0.0001。使用 PCF，双侧腮腺接受的平均剂量较低，但口腔接受的平均剂量较低，BCF 组的平均剂量较低（p<0.0001）。两种成本函数在 PTV 和正常组织并发症概率（NTCP）中均发现相同的肿瘤控制概率（TCP）值（99%）。BCF 组的脊髓=0.5%，脑干=19.1%，大脑=90.7%，而 PCF 组的脊髓=0.3%，脑干=14.9%，大脑=90.7%。发现 BCF 组的治疗时间更短（p=0.005）。
BCF 在适形指数和放射治疗时间方面优于 PCF。然而，PCF 在保护连续器官和实现涉及体积周围更陡峭的剂量下降方面表现更好。建议进行患者特定的临床权衡，以获得满足临床目标的最佳计划。
