乳腺癌保乳术后静态逆向调强与三维适形野中野放疗的剂量学比较

目的 比较早期乳腺癌保乳术后静态逆向调强(IMRT)与三维适形野中野瘤床同步加量(FIF)两种放疗技术的剂量学差异。方法 选择9例左侧早期乳腺癌保乳术后患者,分别设计IMRT与FIF两组放疗计划,处方剂量为乳房靶区50.4 Gy,分28次,每次1.8 Gy;瘤床靶区61.6 Gy,分28次,每次2.2 Gy。比较两组计划的靶区适形度及危及器官受量,并比较两者的计划优化和治疗时间。结果 IMRT的全乳靶区适形度(CI)为1.82±0.16,低于FIF的2.21±0.15(t=2.08,P<0.05);瘤床靶区适形度为1.19±0.04,低于FIF的1.59±0.11(t=3.97,P<0.05)。两组计划危及器官同侧肺的V₂₀和心脏的V₃₀无明显差异。FIF对侧肺的Dmax和Dmean分别是(5.41±2.76)和(0.51±0.10) Gy, IMRT分别为(25.72±2.61)和(7.46±0.39) Gy(t=-22.44、-21.14,P<0.05)。对侧乳房的Dmax和Dmean,FIF为(8.50±5.61)和(0.46±0.11) Gy,IMRT为(27.73±4.29)和(6.38±0.48) Gy(t=-5.66、-14.83,P<0.05)。对于对侧肺和乳房的低剂量照射区V₅,FIF为(0.09±0.09)%和(0.45±0.45)%,低于IMRT的(84.66±3.06)%和(60.79±4.94)%(t=-28.19、-12.80,P<0.05)。在计划优化及治疗时间方面,FIF与IMRT优化时间分别为(61.57±0.89)min和(241.28±1.06)min,单次治疗时间分别为(16.14±1.42)min和(29.85±0.59) min(t=-32.35、-8.82,P<0.05)。结论 IMRT改善了靶区适形度,但是增加了对侧肺和对侧乳房的受照剂量。FIF在计划优化时间及治疗时间方面有优势。

Comparison of dosimetry between inversely optimised intensity-modulated radiotherapy and three-dimensional conformal radiotherapy using the field-in-field after breast-conserving surgery

Objective To compare the dosimetry between inversely optimised intensity-modulated radiotherapy(IMRT) and three-dimensional conformal radiotherapy using the field-in-field technique (FIF) for whole-breast radiotherapy with a boost to the tumor bed after breast-conserving surgery. Methods IMRT and FIF treatment plans were respectively performed and optimised for 9 patients with early stage left-breast cancer after breast-concerving surgery. The prescribed dose of breast was 50.4 Gy in 28 fractions, 1.8 Gy per fraction and that of tumor bed was 61.6 Gy in 28 fractions, 2.2 Gy per fraction. The conformity index, the dose and volume for OAR(organs at risks), time of planning and treatment for the two plans were compared. Results The conformity index(CI)for IMRT was improved compared with the FIF in breast [(1.82±0.16) vs.(2.21±0.15)] and tumor bed [(1.19±0.04) vs.(1.59±0.11), t=2.08, 3.97, P<0.05]. There was no difference for V₂₀ of ipsilateral lung and V₃₀ of heart between two plans. The Dmax and Dmean of the contralateral lung of FIF were (5.41±2.76) and (0.51±0.10) Gy, lower than those of IMRT [(25.72±2.61) and (7.46±0.39) Gy, t=-22.44,-21.14, P<0.05]. The Dmax and Dmean of the contralateral breast of FIF were (8.50±5.61) and (0.47±0.11) Gy, lower than those of IMRT [(27.73±4.30) and (6.38±0.48) Gy, t=-5.66,-14.83, P<0.05]. For FIF, the V₅ of the contralateral lung and breast were (0.09±0.09) % and (0.45±0.45) % , respectively, lower than those of IMRT, which were (84.66±3.06) % and (60.79±4.94)%(t=-28.19,-12.80, P<0.05). The time of optimised plan was (61.57±0.89)min for FIF and(241.28±1.06)min for IMRT (t=-32.35, P<0.05), and that of treatment were (16.14±1.42) min for FIF and (29.85±0.59)min for IMRT (t=-8.82, P<0.05). Conclusions For patients with early stage breast cancer after breast-concerving surgery,IMRT could improve the conformity index of target but increase the dose of contralateral lung and breast. However, FIF has advantage on the time of optimising plan and treatment.