乳腺癌术后胸壁大体积复发二野和六野调强放疗剂量学比较

A dosimetric comparison of the tangential beams IMRT with multifield beams IMRT of the chestwall in postmastectomy breast cancer recurrent patients

目的 比较乳腺癌术后胸壁大体积复发2野和6野调强放疗的计划差异.方法 对8例乳腺切除术后胸壁大体积复发病例,Pinnacle计划系统上分别对PTV进行2野调强和6野调强放疗计划设计,PTV处方剂量为50 Gy/25次（GTV后续计划补量至66～70 Gy）,比较2种计划95％处方剂量PTV适形指数（CI）、均匀性指数（HI）及心脏、同侧肺剂量.结果 6野IMRT计划的CI和HI均优于2野IMRT计划,6野和2野的CI分别为（0.66±0.08）和（0.53±0.10）（t=7.99,P＜0.05）,HI分别为（1.36±0.08）和（2.19±0.78）（t=9.04,P＜0.05）.2个计划中肺V5、V10、V20、V35和心脏Dmax、V35、Dmean值比较差异无统计学意义.结论 乳腺癌切除术后胸壁大体积复发患者行放疗,6野静态逆向调强放疗计划靶区覆盖优于2野,而心肺受量方面无明显差异.

Objective To compare the dose distribution of reserved planned tangential beam IMRT（2-field IMRT） with multifields beams IMRT（6-field IMRT） of the bulk-recurrent chest wall in postmastectomy breast cancer patients. Methods For 8 patients with chest wall in postmastectomy breast cancer bulk-recurrence, 2-field IMRT and 6-field IMRT plans were generated on PTV in Pinnacle Planning System. The prescribed dose of PTV was 50 Gy in 25 fractions and GTV was 66-70 Gy which irradiated incrementally by subsequent plan in 8-10 fractions. The conformal index （CI） and homogeneity index （HI） of 95% of prescribed dose over PTV were compared, while the dose distribution on ipsilateral lung and heart were evaluated. Results The CI of PTV by 6-field IMRT （0.66 ± 0. 08） was higher than that of the 2-field IMRT （0.53 ±0. 10） （t =7.99, P 〈0.05）. The HI of PTV by 6-field IMRT （1.36 ＋0.08） was lower than that of 2-field IMRT （2. 19 ± 0.78） （t = 9.04, P 〈 0.05）. There was no statistical difference in V5, V10, 1：20 and V35 for ipsilateral lung and in D V35 and D for heart between two plans. Conclusions Compared with 2-field IMRT, 6-field IMRT might have a better dose distribution on planning target volume（PTV） for chest wall in postmastectomy breast cancer bulk-recurrence patients, but there is no significant difference in dose-volume of ipsilateral lung and heart between two plans.