Sidhu Manjinder Singh, Singh Kulbir, Sood Sandhya, Aggarwal Ritu
Department of Radiation Oncology, DMCH Cancer Centre, Ludhiana, Punjab, India.
Department of Medical Physics, DMCH Cancer Centre, Ludhiana, Punjab, India.
J Cancer Res Ther. 2023 Jul-Sep;19(5):1267-1271. doi: 10.4103/jcrt.jcrt_11_22.
Aim of radiotherapy is precise dose delivery with objective of achieving maximum local control and minimal toxicity by decreasing dose to organ at risk (OAR).This aim can be achieved by technologies like intensity-modulated radiotherapy (IMRT) and volumetric arc therapy. However, later offers comparable or even better plan quality with shorter treatment time. It is important to note that low dose regions are also a concern due long-term risk of developing a second cancer after radiotherapy. The objective of our study is to do dosimetric comparison of IMRT vs. Rapid arc (RA) plan in gynecology cancer and specifically to assess dose beyond planning target volume (PTV), precisely 5 Gy volume.
Each 20 eligible patients underwent radiotherapy planning on eclipse by both IMRT and RA plans as per institution protocols. Comparative dosimetric analysis of both plans was done by paired sample t-test. PTV metrics compared were D95%, homogenecity index (HI), and conformity index (CI). OAR dose compared were bowel V40 Gy <30%, Rectum V30 Gy <60%, Bladder V45 Gy <35%, and bilateral femur head and neck V30 Gy < 50%. Futhermore, calculated monitor units (MUs) were also compared. Finally, volume of normal tissue beyond the PTV, specifically 5 Gy volume, was compared between plans.
Dosimetric plan comparison showed statistically significant difference in RA and IMRT plans with improved PTV coverage and better OAR tolerance with RA plan. In addition, MU used were significantly less in RA plan, coupled with reduced V5 Gy volume.
In sum, RA plans are dosimetrically significantly better compared to IMRT plans in gynecological malignancies in terms of PTV coverage and OAR sparing. Importantly, not only less MU used but also significantly less normal tissue V5 Gy volume is less in RA compared to IMRT plans.
放射治疗的目的是精确地给予剂量，目标是通过减少危及器官（OAR）的剂量来实现最大程度的局部控制和最小的毒性。这一目标可通过调强放射治疗（IMRT）和容积弧形调强放疗等技术来实现。然而，容积弧形调强放疗能在更短的治疗时间内提供相当甚至更好的计划质量。需要注意的是，由于放疗后发生第二种癌症的长期风险，低剂量区域也是一个问题。我们研究的目的是对妇科癌症中IMRT与容积弧形调强放疗（RA）计划进行剂量学比较，特别是评估计划靶体积（PTV）之外的剂量，精确地说是5 Gy体积。
按照机构方案，20例符合条件的患者分别接受了IMRT和RA计划的放疗计划制定。通过配对样本t检验对两种计划进行比较剂量学分析。比较的PTV指标包括D95%、均匀性指数（HI）和适形指数（CI）。比较的OAR剂量包括肠V40 Gy<30%、直肠V30 Gy<60%、膀胱V45 Gy<35%以及双侧股骨头和颈部V30 Gy<50%。此外，还比较了计算出的监测单位（MU）。最后，比较了计划之间PTV之外正常组织的体积，特别是5 Gy体积。
剂量学计划比较显示，RA和IMRT计划存在统计学显著差异，RA计划的PTV覆盖更好，对OAR的耐受性更佳。此外，RA计划使用的MU显著更少，同时V5 Gy体积也更小。
总之，在妇科恶性肿瘤中，就PTV覆盖和对OAR的保护而言，RA计划在剂量学上明显优于IMRT计划。重要的是，与IMRT计划相比，RA计划不仅使用的MU更少，而且正常组织V5 Gy体积也显著更小。
