乳腺癌改良根治术后放疗降低患侧肺受量的剂量学研究

Dosimetry of different techniques in postmastectomy radiation therapy on the ipsilateral lung

目的 探讨乳腺癌改良根治术后放疗(PMRT)3种照射技术靶区和患侧肺剂量分布的特点,评价其对降低患侧肺受量的作用.方法 对28例Ⅱ、Ⅲ期乳腺癌根治术后患者分别进行胸壁区2个切线适形野(半野)加锁骨上区调强放疗(3D-CRT+ IMRT)、胸壁区加锁骨上区一体调强放疗(IMRT),以及胸壁区2个切线适形野(半野)加锁骨上区电子线单野放疗技术(3D-CRT+ E)的计划设计,通过剂量体积直方图(DVH)评价靶区剂量以及患侧肺V5、V10、V20及V45受照射体积,处方剂量为50.4 Gy(1.8 Gy×28次).结果 靶区适形指数(CI) 3D-CRT+ IMRT组(0.61 ±0.03)和IMRT组(0.62±0.03)之间差异无统计学意义(q=2.16,P＞0.05),这两组CI均优于3DCRT+E组[(0.44±0.02),q=20.50、22.66,P＜0.01]；不均匀指数(HI) 3D-CRT+ IMRT组(1.17±0.02)和IMRT组(1.15±0.02)之间差异无统计学意义(q=1.66,P＞0.05),这两组HI均优于3DCRT+E组[(1.24±0.04),q=3.91、5.58,P＜0.01]；患侧肺V5、V10,3D-CRT+E组(48.70％±3.24％,38.56％±3.70％)、3D-CRT+ IMRT组(49.12％±3.03％,38.38％±3.56％)明显少于IMRT组[(77.18％±8.01％,53.07％±6.85％),q=20.35、20.05、12.10、12.24,P＜0.01],3D-CRT+E、3D-CRT+ IMRT两组之间差异无统计学意义(q =0.30、0.14,P＞0.05)；患侧肺V20,3D-CRT+ IMRT组(26.57％±2.51％)、IMRT组(25.22％±2.77％)优于3D-CRT+E组[(31.79％±3.00％),q=5.27、8.21,P＜0.01],3D-CRT+ IMRT、IMRT两组之间差异无统计学意义(q =2.76,P＞0.05)；V453种计划之间差异无统计学意义(F=0.69,P＞0.05).结论 在PMRT中应用3D-CRT+ IMRT照射技术在不增加设备投入的情况下能有效地降低患侧肺受照射剂量.

Objective To identify the best technique of postmastectomy radiation therapy (PMRT).Methods Twenty-eight patients with stage Ⅱ or Ⅲ invasive breast cancer were treated with modified radical mastectomy and radiotherapy sequaciously involving the supraclavicular region and the chest wall.Three different techniques were developed for each patient:two tangential conformal fields ( half field) in the chest wall plus supraclavicular intensity modulated radiotherapy (3D-CRT + IMRT),integrated chest wall and supraclavicular IMRT(IMRT),and two tangential conformal fields (half field) in the chest wall plus single field electron beam radiotherapy in the supraclavicular region( 3D-CRT + E).The dose distributions of the target areas and the irradiated volumes of the ipsilateral lung ( V5,V10,V20,and V45)were estimated with the dosage volume histogram (DVH).The dosage prescription was 50.4 Gy (1.8 Gy × 28 f).Results The conformity index (CI) of the 3D-CRT + IMRT group was (0.61 ± 0.03),not different from that of the IMRT [ (0.62 ±0.03),q =2.16,P ＞0.05],and the CI levels of these 2 groups were both higher than that of the 3D-CRT + E group [ (0.44 ± 0.02 ),q =20.50,22.66,P ＜0.01 ].The heterogeneity index (HI) of the 3D-CRT + IMRT group was ( 1.17 ±0.02),not different from that of the IMRT [ (1.15 ±0.02),q =1.66,P ＞0.05],and the HI levels of these 2 groups were both lower than that of the 3D-CRT + E group[ ( 1.24 ±0.04),q =3.91,5.58,P ＜0.01 ].The levels of V5 and V10 of the ipsilateral lungs of the 3D-CRT + E group(48.70％ ±3.24％,38％.56％ ±3.70％ ) and 3D-CRT + IMRT group (49.12％ ±3.03％,38.38％ ± 3.56％ ) were all significantly lower than those of the IMRTgroup [(77.18％ ±8.01％,53.07％ ±6.85％),V5,q =20.35,20.05,P＜0.01; V10,q=12.10,12.24,P ＜0.01 ] and there were not significant differences in the V5 and V10 levels between the 3D-CRT + E and 3D-CRT + IMRT groups ( q =0.30,0.14,P ＞ 0.05 ).The levels of V20 of the ipsilateral lungs of the 3D-CRT + IMRT group (26.57％ ±2.51％ )and IMRT group (25.22％ ±2.77％) were all significantly lower that those of the 3D-CRT + E group [ (31.79％ ± 3.00％ ),q =5.27,8.21,P ＜ 0.01 ]and there were not significant differences in the V20 level between the 3D-CRT + IMRT and IMRT groups (q=2.76,P ＞ 0.05 ).There were not significant differences in the V45 levels among these 3 groups (F =0.69,P ＞ 0.05).Conclusions The 3D-CRT + IMRT technique in PMRT effectively reduces the radiated dose on the ipsilateral lung.