Bharati Avinav, Rath Satyajeet, Khurana Rohini, Rastogi Madhup, Mandal Susama R, Gandhi Ajeet Kumar, Hadi Rahat, Srivastava Anoop K, Mishra Surendra Prasad
Department of Radiation Oncology, NCI-AIIMS, New Delhi, India.
Department of Radiation Oncology, Gujarat Cancer and Research Institute, Ahmedabad, India.
J Med Phys. 2023 Jul-Sep;48(3):252-258. doi: 10.4103/jmp.jmp_36_23. Epub 2023 Sep 18.
The purpose of this study was to compare the dosimetric parameters of volumetric modulated arc therapy (VMAT) treatment plans using coplanar and noncoplanar beams in patients with bilateral breast cancer/s (BBCs) in terms of organ at risk sparing and target volume coverage. The hypothesis was to test whether VMAT with noncoplanar beams can result in lesser dose delivery to critical organs such as heart and lung, which will result in lesser overall toxicity.
Data of nine BBC cases treated at our hospital were retrieved. Computed tomography simulation data of these cases was used to generate noncoplanar VMAT plans and the parameters were compared with standard VMAT coplanar plans. Contouring was done using radiation therapy oncology group guidelines. Forty-five Gray in 25 fractions was planned followed by 10 Gy in five fractions boost in breast conservation cases.
No significant difference in planning target volume (PTV) coverage was found for the right breast/chestwall ( = 0.940), left breast/chestwall ( = 0.872), and in the total PTV ( = 0.929). Noncoplanar beams resulted in better cardiac sparing in terms of D heart. The difference in mean dose was >1 Gy (8.80 ± 0.28 - 7.28 ± 0.33, < 0.001). The D, V and V values for total lung slightly favor noncoplanar beams, although there was no statistically significant difference. The average monitor units (MUs) were similar for coplanar plans (1515 MU) and noncoplanar plans (1455 MU), but the overall treatment time was higher in noncoplanar plans due to more complex setup and beam arrangement. For noncoplanar VMAT plans, the mean conformity index was slightly better although the homogeneity indices were similar.
VMAT plans with noncoplanar beam arrangements had significant dosimetric advantages in terms of sparing of critical organs, that is D of heart doses with almost equivalent lung doses and equally good target coverage. Larger studies with clinical implications need to be considered to validate this data.
本研究的目的是比较容积调强弧形放疗（VMAT）治疗计划中，使用共面和非共面射束对双侧乳腺癌（BBC）患者进行治疗时，在危及器官保护和靶区覆盖方面的剂量学参数。假设是测试非共面射束的VMAT是否能减少对心脏和肺等关键器官的剂量输送，从而降低总体毒性。
检索了我院治疗的9例BBC病例的数据。利用这些病例的计算机断层扫描模拟数据生成非共面VMAT计划，并将参数与标准共面VMAT计划进行比较。按照放射肿瘤学组指南进行轮廓勾画。保乳病例计划25次分割给予45 Gy，随后5次分割给予10 Gy的追加剂量。
右乳/胸壁的计划靶区（PTV）覆盖（P = 0.940）、左乳/胸壁的PTV覆盖（P = 0.872）以及总PTV的覆盖（P = 0.929）均未发现显著差异。就心脏剂量（D心脏）而言，非共面射束在心脏保护方面效果更好。平均剂量差异>1 Gy（8.80±0.28 - 7.28±0.33，P < 0.001）。尽管无统计学显著差异，但总肺的Dmean、V20和V30值略倾向于非共面射束。共面计划（1515 MU）和非共面计划（1455 MU）的平均监测单位（MUs）相似，但由于设置和射束排列更复杂，非共面计划的总体治疗时间更长。对于非共面VMAT计划，平均适形指数略好，尽管均匀性指数相似。
非共面射束排列的VMAT计划在关键器官保护方面具有显著的剂量学优势，即心脏剂量的Dmean降低，肺剂量几乎相当，靶区覆盖同样良好。需要考虑开展具有临床意义的更大规模研究来验证该数据。
