CRT+ARC技术在肺癌“T”形靶区患者放射治疗中的剂量学研究

Dosimetric study of conformal radiation therapy+volumetric modulated arc therapy for T-shaped target areas in lung cancer patients

目的:探讨适形放疗(CRT)+容积旋转调强(ARC)在肺癌"T"形靶区放疗计划中的剂量学特点。方法:使用瓦里安计划系统(Eclipse 10.0)对随机选取的15例已行固定野调强放射治疗(FF-IMRT)治疗的肺癌"T"形靶区的患者,采用CRT和ARC设计CRT+ARC计划,采用CRT和FF-IMRT设计CRT+IMRT计划。在满足相同处方剂量要求的情况下,评价和比较两种治疗计划中计划靶区(PTV)的最小剂量(D_(min))、最大剂量(D_(max))、中位剂量、适形度指数(CI)、均匀性指数(HI)和危及器官受量(正常肺的V_5、V_(10)、V_(13)、V_(20)、V_(30)和平均剂量,脊髓D_(max),心脏V_(20)、V_(30)、V_(40)、V_(45)和平均剂量,食管V50、D_(max)),并比较两种治疗计划正常组织B-P受量和总机器跳数。结果:(1)PTV剂量学指标。CRT+ARC计划与CRT+IMRT计划相比,靶区中位值和V107略有升高,具有统计学意义(P=0.000、0.003),其它剂量学指标(PTV的D_(min)、D_(max)、CI、HI)均无统计学意义。(2)危及器官受量。CRT+ARC计划与CRT+IMRT计划相比,脊髓D_(max)有所降低,且具有统计学意义(P=0.000),正常肺的V13有所升高,但不具有统计学意义,正常肺的V_5、V_(10)、V_(20)、V_(30)和平均剂量有所降低,且V_(20)、V_(30)和平均值具有统计学意义(P=0.000、0.020、0.006);其它危及器官受量,食管V50和D_(max),心脏V_(20)、V_(30)、V_(40)、V_(45)和平均剂量,均无统计学意义。(3)正常组织B-P受量。CRT+ARC计划与CRT+IMRT计划相比,V10略有增高,且具有统计学意义(P=0.030);V_(15)、V_(20)、V_(25)和V_(30)有所降低,且具有统计学意义(P=0.000、0.000、0.000、0.001);其它剂量学指标(V_5、V_(35)、V_(40)、V_(45)和V_(50))无统计学意义。(4)机器跳数。CRT+ARC计划和CRT+IMRT计划单次计划中各射野机器跳数累加之和分别为460±59、1 561±180,两者有显著统计学意义(P=0.000)。结论:对于局部晚期或晚期具有"T"形(或"Y"形)靶区的肺癌患者,CRT+ARC计划比CRT+IMRT计划,在靶区剂量分布、保护肺和脊髓方面表现出了优势,明显减少了机器跳数,且肺和正常组织的低剂量受照体积受量未增加,还有一定程度的降低,这对于CRT+ARC技术在临床上应用,具有重要的指导意义。

Objective To discuss the dosimetric characteristics of conformal radiation therapy（CRT）＋volumetric modulated arc therapy（ARC） for T-shaped target areas in patients with lung cancer. Methods Varian treatment planning system（Eclipse 10.0） was used to design CRT＋ARC plan and CRT＋fixed-field intensity-modulated radiotherapy（CRT＋IMRT） plan for T-shaped target areas in 15 lung cancer patients who had been treated with fixed-field IMRT. With the same dose prescription, the minimum dose（D_（min））, maximum dose（Dmax）, median dose, conformity index（CI）, and homogeneity index（HI） of planning target volume（PTV）,and the dose of organs-at-risk（OAR）,（including the V_5, V_（10）, V_（13）, V_（20）, V_（30） and mean dose of normal lung, spinal cord-Dmax, the V_（20）, V_（30）, V_（40）, V_（45） and mean dose of heart, and the V_50 and Dmaxof esophagus） were evaluated and compared between CRT＋ARC plan and CRT＋IMRT plan. And the dose of normal tissues and total monitor units（MU） between the two plans were also compared. Results For the PTV dosimetric index, median dose and V_（10）7 in CRT＋ARC plan increased, compared to those in CRT＋IMRT plan（P=0.000 and 0.003, respectively）, and no statistical differences between the two plans were found in the other dosimetric parameters（D_（min）, Dmax, CI and HI of PTV）. For OAR dose, compared with CRT ＋ IMRT plan, CRT ＋ ARC plan significantly decreased spinal cord-Dmax（P=0.000）, while increased the V_（13） of normal tissue, without statistical significance. Among the decreased V_5, V_（10）, V_（20）, V_（30） and mean dose of normal tissue in CRT＋ARC plan, as comparison with those in CRT＋IMRT plan,the differences in V_（20）, V_（30） and mean dose showed statistical significance（P=0.000, 0.020, 0.006, respectively）. No statistical differences were found in the other OAR dosimetric indexes（the V_50 and Dmaxof esophagus, the V_（20）, V_（30）, V_（40）, V_（45） and mean dose of heart）. For normal tissue B-P dose, compared with CRT＋IMRT plan, CRT＋ARC plan showed slightly increased V_（10） and decreased V_（15）, V_（20）, V25, V_（30）, with statistical differences（P=0.030, 0.000, 0.000, 0.000, 0.001, respectively）. No statistical significances were found in the other dosimetric indexes（V_5, V35, V_（40）, V_（45）, V_50）. The total MU of all beam fields in a fractionated therapy was 460±59, 1 561±180 for CRT＋ARC plan and CRT＋IMRT plan, respectively（P=0.000）. Conclusion For the T-or Y-shaped target areas in the patients with locally advanced or advanced lung cancer, compared with CRT＋IMRT plan, CRT＋ARC plan shows advantages in the dose distribution of target areas and the protection of lung and spinal cord, and significantly decreases MU without increasing or even decreasing the dose of lung, normal tissues and low-dose volume, which provides important guidance for the application of CRT＋ARC in clinical use.