Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, 100730, China.
Tumor Hospital affiliated to Xinjiang Medical University, Urumqi, China.
Radiat Oncol. 2024 Jan 4;19(1):2. doi: 10.1186/s13014-023-02394-2.
To determine the optimal planning target volume (PTV) margins for adequate coverage by daily iterative cone-beam computed tomography (iCBCT)-guided online adaptive radiotherapy (oART) in postoperative treatment of endometrial and cervical cancer and the benefit of reducing PTV margins.
Fifteen postoperative endometrial and cervical cancer patients treated with daily iCBCT-guided oART were enrolled in this prospective phase 2 study. Pre- and posttreatment iCBCT images of 125 fractions from 5 patients were obtained as a training cohort, and clinical target volumes (CTV) were contoured separately. Uniform three-dimensional expansions were applied to the PTVpre to assess the minimum margin required to encompass the CTVpost. The dosimetric advantages of the proposed online adaptive margins were compared with conventional margin plans (7-15 mm) using an oART emulator in another cohort of 125 iCBCT scans. A CTV-to-PTV expansion was verified on a validation cohort of 253 fractions from 10 patients, and further margin reduction and acute toxicity were studied.
The average time from pretreatment iCBCT to posttreatment iCBCT was 22 min. A uniform PTV margin of 5 mm could encompass nodal CTVpost in 100% of the fractions (175/175) and vaginal CTVpost in 98% of the fractions (172/175). The margin of 5 mm was verified in our validation cohort, and the nodal PTV margin could be further reduced to 4 mm if ≥ 95% CTV coverage was predicted to be achieved. The adapted plan with a 5 mm margin significantly improved pelvic organ-at-risk dosimetry compared with the conventional margin plan. Grade 3 toxicities were observed in only one patient with leukopenia, and no patients experienced acute urinary toxicity.
In the postoperative treatment of endometrial and cervical cancer, oART could reduce PTV margins to 5 mm, which significantly decrease the dose to critical organs at risk and potentially lead to a lower incidence of acute toxicity.
为了确定在子宫内膜癌和宫颈癌术后治疗中，使用每日迭代锥形束 CT（iCBCT）引导在线自适应放疗（oART）进行充分覆盖所需的最佳计划靶区（PTV）边界，以及减少 PTV 边界的获益。
这项前瞻性 2 期研究纳入了 15 例接受每日 iCBCT 引导 oART 的术后子宫内膜癌和宫颈癌患者。从 5 例患者的 125 个分次中获取治疗前和治疗后的 iCBCT 图像作为训练队列，并分别勾画临床靶区（CTV）。对 PTVpre 进行统一的三维扩展，以评估包含 CTVpost 所需的最小边界。在另一个 125 个 iCBCT 扫描的队列中，使用 oART 仿真器比较了所提出的在线自适应边界与常规边界计划的剂量学优势。在 10 例患者的 253 个分次的验证队列中验证了 CTV 到 PTV 的扩展，并进一步研究了边界缩小和急性毒性。
从治疗前 iCBCT 到治疗后 iCBCT 的平均时间为 22 分钟。5mm 的均匀 PTV 边界可以包含 100%（175/175）的淋巴结 CTVpost 和 98%（172/175）的阴道 CTVpost。在我们的验证队列中验证了 5mm 的边界，如果预测要达到≥95%CTV 覆盖，则可以进一步将淋巴结 PTV 边界缩小至 4mm。与常规边界计划相比，边界为 5mm 的自适应计划显著改善了骨盆危及器官的剂量学。仅 1 例患者出现白细胞减少的 3 级毒性，没有患者发生急性尿毒性。
在子宫内膜癌和宫颈癌的术后治疗中，oART 可以将 PTV 边界缩小至 5mm，这显著降低了危及器官的剂量，并有潜力降低急性毒性的发生率。
