Portelance L, Chao K S, Grigsby P W, Bennet H, Low D
Department of Radiology, Radiation Oncology Center, Mallinckrodt Institute of Radiology, Washington University Medical Center, St. Louis, MO 63110, USA.
Int J Radiat Oncol Biol Phys. 2001 Sep 1;51(1):261-6. doi: 10.1016/s0360-3016(01)01664-9.
The emergent use of combined modality approach (chemotherapy and radiation therapy) for the treatment of patients with cervical cancer is associated with significant gastrointestinal and genitourinary toxicity. Intensity-modulated radiation therapy (IMRT) has the potential to deliver adequate dose to the target structures while sparing the normal organs and could also allow for dose escalation to grossly enlarged metastatic lymph node in pelvic or para-aortic area without increasing gastrointestinal/genitourinary complications. We conducted a dosimetric analysis to determine if IMRT can meet these objectives in the treatment of cervical cancer.
Computed tomography scan studies of 10 patients with cervical cancer were retrieved and used as anatomic references for planning. Upon the completion of target and critical structure delineation, the imaging and contour data were transferred to both an IMRT planning system (Corvus, Nomos) and a three-dimensional planning system (Focus, CMS) on which IMRT as well as conventional planning with two- and four-field techniques were derived. Treatment planning was done on these two systems with uniform prescription, 45 Gy in 25 fractions to the uterus, the cervix, and the pelvic and para-aortic lymph nodes. Normalization was done to all IMRT plans to obtain a full coverage of the cervix with the 95% isodose curve. Dose-volume histograms were obtained for all the plans. A Student's t test was performed to compute the statistical significance.
The volume of small bowel receiving the prescribed dose (45 Gy) with IMRT technique was as follows: four fields, 11.01 +/- 5.67%; seven fields, 15.05 +/- 6.76%; and nine fields, 13.56 +/- 5.30%. These were all significantly better than with two-field (35.58 +/- 13.84%) and four-field (34.24 +/- 17.82%) conventional techniques (p < 0.05). The fraction of rectal volume receiving a dose greater than the prescribed dose was as follows: four fields, 8.55 +/- 4.64%; seven fields, 6.37 +/- 5.19%; nine fields, 3.34 +/- 3.0%; in contrast to 84.01 +/- 18.37% with two-field and 46.37 +/- 24.97% with four-field conventional technique (p < 0.001). The fractional volume of bladder receiving the prescribed dose and higher was as follows: four fields, 30.29 +/- 4.64%; seven fields, 31.66 +/- 8.26%; and nine fields, 26.91 +/- 5.57%. It was significantly worse with the two-field (92.89 +/- 35.26%) and with the four-field (60.48 +/- 31.80%) techniques (p < 0.05).
In this dosimetric study, we demonstrated that with similar target coverage, normal tissue sparing is superior with IMRT in the treatment of cervical cancer.
宫颈癌患者采用联合治疗方法（化疗和放疗）进行急诊治疗会伴有严重的胃肠道和泌尿生殖系统毒性。调强放射治疗（IMRT）有潜力在保护正常器官的同时向靶区结构给予足够剂量，还能在不增加胃肠道/泌尿生殖系统并发症的情况下对盆腔或腹主动脉旁区域明显肿大的转移性淋巴结进行剂量递增。我们进行了剂量学分析，以确定IMRT在宫颈癌治疗中是否能实现这些目标。
检索10例宫颈癌患者的计算机断层扫描研究资料，并用作计划的解剖学参考。完成靶区和关键结构勾画后，将影像和轮廓数据传输至IMRT计划系统（Corvus，Nomos）和三维计划系统（Focus，CMS），在这两个系统上得出IMRT以及采用两野和四野技术的传统计划。在这两个系统上进行治疗计划，对子宫、宫颈、盆腔和腹主动脉旁淋巴结给予统一处方剂量45 Gy，分25次照射。对所有IMRT计划进行归一化处理，以使95%等剂量曲线完全覆盖宫颈。获取所有计划的剂量体积直方图。进行Student t检验以计算统计学显著性。
采用IMRT技术接受处方剂量（45 Gy）的小肠体积如下：四野，11.01±5.67%；七野，15.05±6.76%；九野，13.56±5.30%。这些均显著优于两野（35.58±13.84%）和四野（34.24±17.82%）传统技术（p<0.05）。接受大于处方剂量的直肠体积分数如下：四野，8.55±4.64%；七野，6.37±5.19%；九野，3.34±3.0%；相比之下，两野为84.01±18.37%，四野传统技术为46.37±24.97%（p<0.001）。接受处方剂量及更高剂量的膀胱体积分数如下：四野，30.29±4.64%；七野，31.66±8.26%；九野，26.91±5.57%。两野（92.89±35.26%）和四野（60.48±31.80%）技术的情况明显更差（p<0.05）。
在这项剂量学研究中，我们证明在宫颈癌治疗中，在靶区覆盖相似的情况下，IMRT对正常组织的保护更优。
