左乳腺癌保乳术后瘤床同步加量静态调强放射治疗与断层定野放射治疗的剂量学研究

Dosimetric study of sIMRT and TOMO fixed field irradiation (TD) simultaneous integrated boost on tumor bed for patients receiving left breast-conserving surgery

摘要:

目的 探讨左乳腺癌保乳术后瘤床同步加量静态调强放射治疗（sIMRT）与断层定野放射治疗（TD）的剂量学特点。方法 选取2016年5月—2018年5月云南省肿瘤医院左乳腺癌保乳术后瘤床银夹标记患者24例，对同一患者分别采用sIMRT计划设计（Monaco5.11.03治疗计划系统）和TD计划设计（TomoTherapy治疗计划系统），比较两种计划的剂量学参数。结果 两组计划的肿瘤计划靶区（PGTV）的D_2%、D_98%、适形指数（CI）、均匀性指数（HI）比较，差异均有统计学意义（P <0.05），sIMRT的CI（0.75±0.05）高于TD的CI（0.61±0.13），TD的HI（0.04±0.01）低于sIMRT的HI（0.05±0.00）（P <0.05）。D_50%组间差异无统计学意义（P >0.05）。两组计划的乳腺计划靶区（PTV）的D_98%、CI、HI比较，差异均有统计学意义（P <0.05），sIMRT的CI（0.82±0.04）高于TD的CI（0.68±0.05），TD的HI（0.19±0.01）低于sIMRT的HI（0.20±0.01）（P <0.05），D_2%、D_50%组间差异均无统计学意义（P >0.05）。在危及器官的比较上，sIMRT较TD降低了左肺的V₅、V₂₀、D_mean以及左右心室的D_mean（P <0.05），其中sIMRT左肺的V₅、V₂₀和D_mean较TD分别降低了3.69%、1.26%、7.84%。TD较sIMRT降低了对侧乳腺的D_mean、心脏的V₃₀、左右心房的D_mean及脊髓的D_2%（P <0.05）。但在心脏的D_mean方面两者组间差异无统计学意义（P >0.05）。结论 sIMRT技术和TD技术均能满足左乳腺癌保乳术后放疗的剂量需求，sIMRT技术的CI优于TD技术的CI，TD技术的HI优于sIMRT技术的HI；sIMRT技术对患侧肺的保护更佳，对于有肺部基础疾病的患者，建议优先选择sIMRT技术；TD技术对心脏的保护并未体现出明显优势。

Abstract:

Objective To discuss the dosimetric characteristics of simultaneous integrated boost sIMRT and TD on the tumor bed after breast-conserving surgery for left breast cancer.Methods Twenty-four patients who were marked by silver clips on the tumor bed after breast-conserving surgery for left breast cancer were selected. For the same patient, the Monaco5.11.03 treatment planning system was used for the sIMRT plan design, and the Tomo Therapy treatment planning system was used for the TD plan design. The dosimetry parameters of the two plans were compared.Results The differences in D_2%, D_98%, CI, and HI of planned tumor planning target volume (PGTV) between the two groups were statistically significant (P < 0.05). The CI of sIMRT (0.75 ± 0.05) was higher than that of TD (0.61 ± 0.13), and the HI of TD (0.04 ± 0.01) was lower than sIMRT (0.05 ± 0.00) (P < 0.05). The difference in D_50% was not statistically significant (P > 0.05). The differences in D_98%, CI, and HI of the breast plan target volume (PTV) between the two groups were statistically significant (P < 0.05). The CI of sIMRT (0.82 ± 0.04) was higher than that of TD (0.68 ± 0.05), and the HI of TD (0.19 ± 0.01) was lower than sIMRT (0.20 ± 0.01) (P < 0.05). The difference in D_2%, D_50% was not statistically significant (P > 0.05). In comparison with organs at risk, compared with TD, sIMRT reduced V₅, V₂₀, Dmean in the left lung and, Dmean in the left and right ventricles (P < 0.05). The V₅, V₂₀ and D_mean of the left lung of sIMRT were reduced by 3.69%, 1.26%, and 7.84% respectively, compared with TD. Compared with sIMRT, TD reduced the D_mean of the contralateral breast, V₃₀ of the heart, D_mean of the left and right atrium, and D_2% of the spinal cord (P < 0.05). However, there was no statistically significant difference in the D_mean of the heart (P > 0.05).Conclusion Both sIMRT technology and TD technology can meet the dose requirements of postoperative radiotherapy for left breast cancer. The CI of the former is better than the latter, and the HI of the latter is better than the former; sIMRT technology can better protect the affected lung. For patients with underlying lung diseases, sIMRT technology is recommended to be preferred. The protection of the heart by TD technology does not show obvious advantages.