Department of Radiation Oncology, Cancer Center, Peking University Third Hospital, Beijing, China.
Int J Gynecol Cancer. 2009 Dec;19(9):1574-9. doi: 10.1111/IGC.0b013e3181bd35a6.
Conventional whole pelvic radiotherapy (WPRT) with 3-dimensional conformal radiotherapy (3D-CRT) exposes most of the contents of the true pelvis to the prescribed dose. Intensity-modulated radiation therapy (IMRT) provides more conformal dose distribution and better sparing of critical structures for WPRT. However, IMRT is more complicated in planning and delivery, requiring more expensive equipment and time-consuming quality assurance. We explore and evaluate a novel conformal arc radiotherapeutic technique for postoperative WPRT for endometrial cancer in this study.
This technique involves 2-axis conformal arc therapy (2A-CAT) with 180-degree rotation around 2 isocenters each in 2 separate dose-shaping structures. Dosimetric comparison with 3D-CRT and IMRT for 10 endometrial cancer patients undergoing postoperative WPRT was performed to evaluate this new 2A-CAT technique.
The mean conformity indices were 0.83, 0.61, and 0.88 for 2A-CAT, 3D-CRT, and IMRT, respectively. The mean homogeneity indices were 1.15, 1.08, and 1.10. The mean doses to bowel, rectum, bladder, and pelvic bone marrow were, respectively, 1.19, 3.39, 4.65, and 1.64 Gy lower with 2A-CAT than with 3D-CRT (P < 0.05), whereas a little higher than with IMRT. The mean dose to normal tissue was 1.87 Gy higher with 2A-CAT than with IMRT (P = 0.00).
In postoperative WPRT for endometrial cancer, 2A-CAT significantly improves the dose conformity and sparing of bowel, rectum, and bladder compared with 3D-CRT. Despite dose uniformity and conformity being still inferior to those of IMRT, its simplicity and extensive availability combined with further improvement warrant it as a potential shortcut alternative to IMRT.
传统的三维适形放疗（3D-CRT）的全盆腔放疗（WPRT）会将真骨盆的大部分内容暴露于规定剂量下。调强放疗（IMRT）可为 WPRT 提供更适形的剂量分布，并更好地保护关键结构。然而，IMRT 在计划和实施方面更加复杂，需要更昂贵的设备和耗时的质量保证。我们在这项研究中探索并评估了一种新的用于子宫内膜癌术后 WPRT 的适形弧形放射治疗技术。
该技术涉及两个轴的适形弧形治疗（2A-CAT），每个 2 个单独的剂量成型结构中有 2 个中心点各进行 180 度旋转。对 10 例接受术后 WPRT 的子宫内膜癌患者进行了 3D-CRT 和 IMRT 的剂量比较，以评估这种新的 2A-CAT 技术。
2A-CAT、3D-CRT 和 IMRT 的平均适形性指数分别为 0.83、0.61 和 0.88。平均均匀性指数分别为 1.15、1.08 和 1.10。与 3D-CRT 相比，2A-CAT 使肠道、直肠、膀胱和骨盆骨髓的平均剂量分别降低了 1.19、3.39、4.65 和 1.64 Gy（P<0.05），而与 IMRT 相比则略高。与 IMRT 相比，2A-CAT 使正常组织的平均剂量增加了 1.87 Gy（P=0.00）。
在子宫内膜癌的术后 WPRT 中，2A-CAT 与 3D-CRT 相比，显著提高了肠道、直肠和膀胱的剂量适形性和保护效果。尽管剂量均匀性和适形性仍不如 IMRT，但由于其简单性和广泛适用性，加上进一步的改进，使其成为 IMRT 的潜在替代方案。
