Department of Radiation Oncology, Princess Margaret Hospital-University Health Network, Toronto, Canada.
Radiat Oncol. 2006 May 4;1:13. doi: 10.1186/1748-717X-1-13.
To evaluate intensity-modulated radiation therapy (IMRT) as an alternative to conformal radiotherapy (CRT) or 4-field box boost (4FB) in women with gynecologic malignancies who are unsuitable for brachytherapy for technical or medical reasons.
Dosimetric and toxicity information was analyzed for 12 patients with cervical (8), endometrial (2) or vaginal (2) cancer previously treated with external beam pelvic radiotherapy and a CRT boost. Optimized IMRT boost treatment plans were then developed for each of the 12 patients and compared to CRT and 4FB plans. The plans were compared in terms of dose conformality and critical normal tissue avoidance.
The median planning target volume (PTV) was 151 cm(3) (range 58-512 cm(3)). The median overlap of the contoured rectum with the PTV was 15 (1-56) %, and 11 (4-35) % for the bladder. Two of the 12 patients, both with large PTVs and large overlap of the contoured rectum and PTV, developed grade 3 rectal bleeding. The dose conformity was significantly improved with IMRT over CRT and 4FB (p < or = 0.001 for both). IMRT also yielded an overall improvement in the rectal and bladder dose-volume distributions relative to CRT and 4FB. The volume of rectum that received the highest doses (>66% of the prescription) was reduced by 22% (p < 0.001) with IMRT relative to 4FB, and the bladder volume was reduced by 19% (p < 0.001). This was at the expense of an increase in the volume of these organs receiving doses in the lowest range (<33%).
These results indicate that IMRT can improve target coverage and reduce dose to critical structures in gynecologic patients receiving an external beam radiotherapy boost. This dosimetric advantage will be integrated with other patient and treatment-specific factors, particularly internal tumor movement during fractionated radiotherapy, in the context of a future image-guided radiation therapy study.
评估调强放疗（IMRT）作为一种替代技术，用于因技术或医学原因不适合近距离放疗的妇科恶性肿瘤患者。
对 12 例宫颈癌（8 例）、子宫内膜癌（2 例）或阴道癌（2 例）患者进行了分析，这些患者在接受盆腔外照射放疗和 CRT 加量放疗后，接受了调强放疗加量治疗。然后为每位患者制定了优化的 IMRT 加量治疗计划，并与 CRT 和 4FB 计划进行了比较。从剂量适形性和关键正常组织避免两个方面比较了这些计划。
中位计划靶区（PTV）为 151cm³（范围 58-512cm³）。直肠与 PTV 轮廓的重叠中位数为 15%（1-56%），膀胱为 11%（4-35%）。12 例患者中有 2 例发生 3 级直肠出血，这 2 例患者的 PTV 均较大，且直肠与 PTV 轮廓的重叠也较大。与 CRT 和 4FB 相比，IMRT 的剂量适形性显著提高（p<0.001）。与 CRT 和 4FB 相比，IMRT 还改善了直肠和膀胱的剂量-体积分布。直肠接受最高剂量（>66%处方剂量）的体积减少了 22%（p<0.001），膀胱体积减少了 19%（p<0.001）。这是以增加这些器官接受最低剂量范围（<33%）的体积为代价的。
这些结果表明，IMRT 可以提高靶区覆盖范围，降低接受外照射放疗加量的妇科患者关键结构的剂量。在未来的图像引导放疗研究中，将结合其他患者和治疗特定因素，特别是分次放疗过程中的肿瘤内部运动，对这种剂量学优势进行评估。
