The impact of intensity modulated radiotherapy on the skin dose for deep seated tumors

Objective: The purpose of this study was to investigate the impact of intensity modulated radiotherapy (IMRT) on surface doses for brain, abdomen and pelvis deep located tumors treated with 6 MV photon and to evaluate the skin dose calculation accuracy of the XIO 4.04 treatment planning system. Methods: More investigations for the influences of IMRT on skin doses would increase its applications for many treatment sites. Measuring skin doses in real treatment situations would reduce the uncertainty of skin dose prediction. In this work a pediatric human phantom was covered by a layer of 1 mm bolus at three treatment sites and thermoluminescent dosimeter (TLD) chips were inserted into the bolus at each treatment site before CT scan. Two different treatment plans [three-dimensional conformal radiation therapy (3DCRT) and IMRT] for each treatment sites were performed on XIO 4.04 treatment planning system using superposition algorism. Results: The results showed that the surface doses for 3DCRT were higher than the surface doses in IMRT by 1.6%, 2.5% and 3.2% for brain, abdomen and pelvis sites respectively. There was good agreement between measured and calculated surface doses, where the calculated surface dose was 15.5% for brain tumor calculated with 3DCRT whereas the measured surface dose was 12.1%. For abdomen site the calculated surface dose for IMRT treatment plan was 16.5% whereas the measured surface dose was 12.6%. Conclusion: The skin dose in IMRT for deep seated tumors is lower than that in 3DCRT which is another advantage for the IMRT. The TLD readings showed that the difference between the calculated and measured point dose is negligible. The superposition calculation algorism of the XIO 4.04 treatment planning system modeled the superficial dose well.

Helical tomotherapy and volumetric modulated arc therapy:New therapeutic arms in the breast cancer radiotherapy

AIM To analyse clinical and dosimetric results of helical tomotherapy(HT) and volumetric modulated arc therapy(VMAT) in complex adjuvant breast and nodes irradiation.METHODS Seventy-three patients were included(31 HT and 42 VMAT). Dose were 63.8 Gy(HT) and 63.2 Gy(VMAT) in the tumour bed, 52.2 Gy in the breast, 50.4 Gy in supraclavicular nodes(SCN) and internal mammary chain(IMC) with HT and 52.2 Gy and 49.3 Gy in IMC and SCN with VMAT in 29 fractions. Margins to particle tracking velocimetry were greater in the VMAT cohort(7 mm vs 5 mm).RESULTS For the HT cohort, the coverage of clinical target volumes was as follows: Tumour bed: 99.4% ± 2.4%; breast: 98.4% ± 4.3%; SCN: 99.5% ± 1.2%; IMC:96.5% ± 13.9%. For the VMAT cohort, the coverage was as follows: Tumour bed: 99.7% ± 0.5%, breast: 99.3% ± 0.7%; SCN: 99.6% ± 1.4%; IMC: 99.3% ± 3%. For ipsilateral lung, Dmean and V20 were 13.6 ± 1.2 Gy, 21.1% ± 5%(HT) and 13.6 ± 1.4 Gy, 20.1% ± 3.2%(VMAT). Dmean and V30 of the heart were 7.4 ± 1.4 Gy, 1% ± 1%(HT) and 10.3 ± 4.2 Gy, 2.5% ± 3.9%(VMAT). For controlateral breast Dmean was 3.6 ± 0.2 Gy(HT) and 4.6 ± 0.9 Gy(VMAT). Acute skin toxicity grade 3 was 5% in the two cohorts.CONCLUSION HT and VMAT in complex adjuvant breast irradiation allow a good coverage of target volumes with an acceptable acute tolerance. A longer follow-up is needed to assess the impact of low doses to healthy tissues.

Simultaneous modulated accelerated radiation therapy for esophageal cancer:A feasibility study

AIM: To establish the feasibility of simultaneous modulated accelerated radiation therapy (SMART) in esophageal cancer (EC).

5-氟尿嘧啶为基础的化疗方案联合三维适形调强放疗用于进展期胃癌术后的临床观察

目的:观察5-氟尿嘧啶(5-FU)为基础的化疗方案联合三维适形调强放疗用于进展期胃癌术后的疗效和安全性。方法:110例行根治切除的进展期胃癌患者随机分为对照组(55例)和序贯组(55例)。对照组患者给予5-FU注射液400 mg/(m^2·d),静脉推注后,再给予600 mg/m^2持续泵注22 h,d1~2+注射用盐酸吡柔比星50 mg,静脉滴注,d1+注射用奥沙利铂150 mg,静脉滴注,d1;序贯组患者在对照组治疗的基础上加用三维适形调强放疗,于第4个化疗周期后开始行三维适形调强放疗2周,总剂量DT40~45 Gy/1.8 Gy/24~25F。两组均以3周为1个周期,共治疗6个周期。随访两组患者1、2、3年总生存率及无进展生存率,转移率及Ⅲ~Ⅳ度不良反应发生情况。结果:序贯组患者随访1、2、3年总生存率和随访1、2、3年无进展生存率均显著高于对照组,序贯组患者淋巴结转移率和远处转移率均显著低于对照组,差异均有统计学意义(P<0.05)。两组患者Ⅲ~Ⅳ度恶心呕吐、脱发、骨髓抑制发生率比较,差异均无统计学意义(P>0.05)。结论:5-FU为基础化疗方案联合三维适形调强放疗可延长进展期胃癌术后患者的生存时间,降低远期转移率,且安全性相当。

胸中段食管癌三维适形放疗与简化调强放疗技术的剂量学比较

目的：评估三维适形放疗与简化调强放疗两种不同放疗技术在胸中段食管癌放射治疗中的优缺点。方法20例胸中段食管癌患者分别进行3DCRT和sIMRT两种放疗计划设计，处方剂量均为66 Gy/33 f。比较两组计划的靶区与危及器官剂量学参数及加速器跳数（ MU）。结果 sIMRT在PTV的剂量覆盖、均一性及适形度均优于3DCRT（P＜0．05）；3DCRT与sIMRT的双肺V30 Gy及双肺V20 Gy分别为11．61±3．68 vs．10．33±3．02（P＝0．010）和23．37±8．38 vs．18．89±4．45（P＝0．001）。两组的双肺V5 Gy无显著性差异。3DCRT与sIMRT的MU分别为542．24±76．32和530．80±97．13（P＝0．677）。结论与3DCRT相比，sIMRT有较满意的PTV高剂量覆盖及均匀的剂量分布。在危及器官保护方面，sIM-RT的双肺高剂量区范围明显低于3DCRT。两组计划的MU无显著性差异。