Nithya L, Goel Vineeta, Sharma Deepti, Vittal Karthik, Marjara Nidhi
Department of Radiation Oncology, Max Super Speciality Hospital, Shalimarbagh, New Delhi, India.
Department of Radiation Oncology, Institute of Liver and Biliary Sciences, New Delhi, India.
J Med Phys. 2020 Jul-Sep;45(3):148-155. doi: 10.4103/jmp.JMP_49_20. Epub 2020 Oct 13.
This planning study compared the various dosimetric parameters of different types of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques for left-sided breast cancer radiotherapy.
Treatment of 22 left-sided breast cases was planned using two IMRT and VMAT techniques for the prescription of 40 Gy in 15 fractions. For tangential IMRT (Tan_IMRT), five beams were placed as conventional tangential beams. For equally spaced IMRT (Equi_IMRT), six beams were placed equidistantly at 40° interval from 300° to 140°. For tangential VMAT (Tan_VMAT), two arcs were used with the avoidance sector in such a way that the beam covered like tangential fields. For full-arc VMAT (Full_VMAT), similar arcs as Tan_VMAT were used, without avoidance sector. All treatment plans were generated using Eclipse planning system for TrueBeam STx linear accelerator. For planning target volume (PTV), dose parameters including D, D, V homogeneity index (HI), and conformity index (CI) were analyzed. Different dose parameters for the left lung, heart, left anterior descending artery (LAD), right lung, and right breast were also analyzed. In addition, low-dose spillage in the normal tissues and the number of monitor units (MUs) required for the treatment were compared.
IMRT technique exhibited superior D and D for PTV compared with VMAT techniques. VMAT plans provided more V (6%) compared with that of IMRT plans (approximately 1%). HI was better in IMRT plans (Tan_IMRT, 0.085 ± 0.015; Equi_IMRT, 0.094 ± 0.011) than in VMAT plans. CI was better in VMAT plans. The mean lung dose (7.7 Gy ± 1.788 Gy) and V (34.99% ± 6.799%) were better achieved in Tan_IMRT plan than other plans. Right lung, heart, and right breast sparing were better achieved in Tan_IMRT plan. Moreover, low-dose spillage was very less in the Tan_IMRT compared with all other techniques.
Dosimetric comparison in this study showed that tangential IMRT technique is superior in terms of target coverage, sparing of lung, heart, and right breast, and low-dose spillage control in the left-sided breast-only radiotherapy.
本规划研究比较了不同类型的调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）技术用于左侧乳腺癌放射治疗的各种剂量学参数。
采用两种IMRT和VMAT技术对22例左侧乳腺癌病例进行治疗计划，处方剂量为40 Gy，分15次照射。对于切线IMRT（Tan_IMRT），如传统切线野那样设置5个射野。对于等间距IMRT（Equi_IMRT），以300°至140°每隔40°等间距设置6个射野。对于切线VMAT（Tan_VMAT），使用两个弧形野并设置避让野，使射野覆盖类似切线野。对于全弧VMAT（Full_VMAT），使用与Tan_VMAT类似的弧形野，不设置避让野。所有治疗计划均使用Eclipse治疗计划系统在TrueBeam STx直线加速器上生成。对于计划靶体积（PTV），分析包括D、D、体积均匀性指数（HI）和适形指数（CI）在内的剂量参数。还分析了左肺、心脏、左前降支动脉（LAD）、右肺和右乳腺的不同剂量参数。此外，比较了正常组织中的低剂量溢出情况以及治疗所需的监测单位（MU）数量。
与VMAT技术相比，IMRT技术在PTV的D和D方面表现更优。VMAT计划的V（6%）比IMRT计划（约1%）更高。IMRT计划的HI更好（Tan_IMRT，0.085±0.015；Equi_IMRT，0.094±0.011），而VMAT计划的CI更好。Tan_IMRT计划在平均肺剂量（7.7 Gy±1.788 Gy）和V（34.99%±6.799%）方面比其他计划实现得更好。Tan_IMRT计划在右肺、心脏和右乳腺的保护方面表现更好。此外，与所有其他技术相比，Tan_IMRT的低剂量溢出非常少。
本研究中的剂量学比较表明，在仅左侧乳腺癌放射治疗中，切线IMRT技术在靶区覆盖、肺、心脏和右乳腺的保护以及低剂量溢出控制方面具有优势。
